impact of jet experiment manual

Prepare for your exams

• Guidelines and tips

Study with the several resources on Docsity

Earn points by helping other students or get them with a premium plan

Prepare for your exams with the study notes shared by other students like you on Docsity

The best documents sold by students who completed their studies

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

For each uploaded document

For each given answer (max 1 per day)

Choose a premium plan with all the points you need

Study Opportunities

Connect with the world's best universities and choose your course of study

Ask the community for help and clear up your study doubts

Discover the best universities in your country according to Docsity users

Free resources

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

From our blog

Experiment # 5 - Impact of Jet, Lab Reports of Fluid Mechanics

Experiment # 5 - Impact of Jet

Typology: Lab Reports

Limited-time offer

Uploaded on 03/04/2021

81 documents

On special offer

Related documents

Partial preview of the text.

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

Book Title: Applied Fluid Mechanics Lab Manual

Authors: Habib Ahmari and Shah Md Imran Kabir

Download this book

• Digital PDF
• Pressbooks XML
• Common Cartridge (Web Links)
• Common Cartridge (LTI Links)

Book Description: This lab manual provides students with the theory, practical applications, objectives, and laboratory procedure of ten experiments. The manual also includes educational videos showing how student should run each experiment and a workbook for organizing data collected in the lab and preparing result tables and charts.

Book Information

Book description.

Basic engineering knowledge about fluid mechanics is required in various sectors of water resources engineering, such as designing hydraulic structure on any riverine environments and flood mitigation process. The objective of this book is to enable students to understand fundamental concepts in the field of fluid mechanics and apply those concepts in practice. Applied Fluid Mechanics Lab Manual is designed to enhance civil engineering students’ understanding and knowledge of experimental methods and basic principles of fluid mechanics. The ten experiments in this lab manual provide an overview of widely used terms and phenomena of fluid mechanics and open channel flow, which are required for solving engineering problems.

Applied Fluid Mechanics Lab Manual Copyright © 2019 by Habib Ahmari and Shah Md Imran Kabir is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

Engineering: general

• No category

Impact of a Jet

Related documents.

Add this document to collection(s)

You can add this document to your study collection(s)

Add this document to saved

You can add this document to your saved list

Suggest us how to improve StudyLib

(For complaints, use another form )

Input it if you want to receive answer

Academia.edu no longer supports Internet Explorer.

To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to  upgrade your browser .

Enter the email address you signed up with and we'll email you a reset link.

• We're Hiring!
• Help Center

Download Free PDF

EXPERIMENT NO. 3 IMPACT OF JET

Objective: To verify the momentum equation experimentally through impact of jet experiment. Apparatus Required: Impact of jet apparatus, weights and stop watch. Theory: The momentum equation based on Newton's 2 nd law of motion states that the algebraic sum of external forces applied to control volume of fluid in any direction equal to the rate of change of momentum in that direction. The external forces include the component of the weight of the fluid and of the forces exerted externally upon the boundary surface of control volume. If a vertical water jet moving with velocity 'V' made to strike a target (Vane) which is free, to move in vertical direction, force will be exerted on the target by the impact of jet. Applying momentum equation in z-direction, force exerted by the jet on the vane, Fz is given by F = ρQ (Vz out-V Z in) For flat plate, V z out = 0 F z = ρQ (0-v) F Z = ρQv For hemispherical curved plate, v z out =-v, v z in = v F z = ρQ [v+ (-v)] F Z = 2 ρQv Where Q= Discharge from the nozzle (Calculated by volumetric method) V= Velocity of jet = (Q/A) Experimental setup: The set up primarily consists of a nozzle through which jet emerges vertically in such a way that it may be conveniently observed through the transparent cylinder. It strikes the target plate or disc positioned above it. An arrangement is made for the movement of the plate under the action of the jet and also because of the weight placed on the loading pan. A scale is provided to carry the plate to its original position i.e. as before the jet strikes the plate. A collecting tank is utilized to find the actual discharge and velocity through nozzle.

Free related PDFs Related papers

This thesis work includes determination of the impact of a jet, incorporating the design and fabrication of the impact of jet apparatus. An impact of jet apparatus is used to investigate the reaction force produced by the impact of a jet of water on to various target vanes. This impact of jet apparatus will be used for carrying out experiments in the Fluid Machinery Laboratory. This thesis work provides detailed performance measurements of an impact of jet operation. This experiment addresses the study and determination of the reaction forces exerted by a jet of water impacting against stationary deflectors and to compare the experimental results to the theoretical results. The deflectors used in the experiment can be categorized into four geometries. A flat plate, a conical cup, a semi-hemispherical and a combined conical and hemispherical cup are used as deflectors in the experiment. The measurements include the varied flow rates, the velocity of water at nozzle output and the angles of the exit velocities of water from which the corresponding reaction forces are computed. The reaction forces are calculated both experimentally and theoretically and the results are presented graphically. The results and properties of the graphs are used to compare among the reaction forces of each deflectors or vanes.

This papers discuss the experiment in an hydraulic lab

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

JOHN WILEY & SONS, INC., 2011

•   We're Hiring!
•   Help Center
• Find new research papers in:
• Health Sciences
• Earth Sciences
• Cognitive Science
• Mathematics
• Computer Science
• Academia ©2024

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 23 September 2024

Impact of different disinfection protocols on the bond strength of NeoMTA 2 bioceramic sealer used as a root canal apical plug (in vitro study)

• Nada Omar 1 ,
• Nihal Refaat Kabel 2 ,
• Muhammad Abbass Masoud 3 &
• Tamer M. Hamdy   ORCID: orcid.org/0000-0003-0948-194X 1  

BDJ Open volume  10 , Article number:  75 ( 2024 ) Cite this article

35 Accesses

Metrics details

• Calcium-based cement
• Root canal treatment

Introduction

Treatment of an immature permanent tooth required a special disinfection protocol due to the presence of thin radicular walls, which are prone to fracture. Mineral Trioxide Aggregate (MTA) has been proposed as a root repair material for root canal treatment. The aim of this in vitro study was to compare the push-out bond strength of conventional White MTA cements and second generation NeoMTA 2 in imitated immature roots treated with different disinfection protocols, which are 5.25% sodium hypochlorite (NaOCl), followed by 17% ethylenediaminetetraacetic acid (EDTA), and NaOCl, followed by 20% etidronic acid (HEBP).

The root canals of freshly extracted single-root teeth were manually prepared until 90 K-file to imitate immature roots. Roots were randomly divided into four groups (G) according to the disinfection protocol ( n  = 15 per group). where G1 (NaOCl + EDTA + White MTA) and G2 (NaOCl + EDTA + NeoMTA 2) While G3 (NaOCl + HEBP + White MTA) and G4 (NaOCl + HEBP + NeoMTA 2) All groups were activated with manual agitation. All specimens were incubated for 48 h. The apical third of each root was perpendicularly sectioned to attain a slice of 3 mm thickness. Push-out bond strength values were assessed using a two-way ANOVA and a Student’s t test.

G3 and G4 that were treated with HEPB showed higher significant push-out bond strength mean values than G1 and G2 treated with an EDTA chelating agent. Irrespective of the chelating agent used, it was found that both NeoMTA 2 and White MTA had no significant influence on push-out bond strength mean values ( p  ≤  0.05 ).

The combined use of 5.25% NaOCl and 20% HEBP increased the push-out strength values of both NeoMTA 2 and White MTA, rendering them suitable to be used as an alternative chelating agent to EDTA.

Similar content being viewed by others

Biocompatibility of mineral trioxide aggregate and biodentine as root-end filling materials: an in vivo study

A matched irrigation and obturation strategy for root canal therapy

Efficacy of various techniques in calcium silicate-based intracanal medicament removal: a micro-CT analysis

Innovations in the root canal treatment comprise improvements in root canal filling materials, root canal irrigants, and instrumentation to achieve a suitable apical seal and convenient root canal treatment [ 1 , 2 , 3 , 4 , 5 ]. Treatment options for necrotic, immature permanent teeth include revascularization and apexification [ 6 , 7 , 8 ]. It has been demonstrated that revascularization of non-vital, immature roots is suggested in cases where deep caries or trauma has interrupted the normal root canal development [ 7 , 8 ]; however, in other cases, it is not recommended and may lead to failure [ 9 , 10 ]. In these situations, induction of apical closure utilizing the one-visit apexification technique by using a biocompatible, insoluble, and osteoconductive material, such as mineral trioxide aggregate (MTA), is becoming more reliable. where an apical plug is applied, filling the apical part of the immature root canals, which produce more favorable conditions for conventional root canal filling [ 10 ], and inducing an apical hard tissue matrix [ 11 , 12 ].

MTA contains dicalcium and tricalcium silicate particles that set in a damp environment, forming calcium silicate hydrate. It is usually used in pulp capping, pulpotomy, root perforation repair, pulp regeneration, and root end filling materials [ 13 , 14 , 15 , 16 ]. However, its prolonged setting time, staining of the teeth, and difficulty in manipulation limit its use [ 17 ]. NeoMTA 2 is the second generation of NeoMTA, whose prototype was NeoMTA Plus [ 18 ]. It was developed to be a multipurpose root and pulp treatment material that is quicker to mix, whiter, higher radiopacity, and suitable for all procedures [ 18 ]. It is a fast-setting, bioactive, and non-staining material with easier manipulation to overcome the MTA drawbacks. It is resin-free for extreme MTA concentration and highest calcium and hydroxide ions release and maximum bioactivate potentiality [ 19 ]. Its unique gel properties ensure that the cement remains in place without being washed out. It doesn’t stain the teeth as it contains tantalum oxide as a radio-opacifier instead of bismuth oxide to overcome the discoloration potential [ 20 , 21 , 22 ]. It is composed of extremely fine, inorganic powder of tricalcium and dicalcium silicate with tantalum oxide and aluminum as a radiopacifying agent instead of bismuth oxide to overcome its well-known discoloration potential [ 18 , 23 ].

Prior to starting the apexification procedures, disinfection of the canal is of prime importance because, in most cases, necrotic pulps are infected [ 24 , 25 , 26 ]. The primary phase of treatment is to disinfect the necrotic root canals to establish periapical healing [ 26 ]. It has been advocated that copious irrigation using sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA) be used for proper chemo-mechanical preparation, to control the microorganisms and their byproducts, to dissolve the necrotic tissue, and to remove the smear layer created during instrumentation [ 27 , 28 , 29 , 30 ]. Nevertheless, it was observed that the physical, chemical, and structural properties of dentin were altered when in contact with this combination of irrigants. NaOCl decreases the dentin microhardness, causing irreversible erosion of the dentin microstructure [ 31 , 32 , 33 ], denaturing the collagen components of the dentin surface and oxidizing the organic matrix. EDTA can change the ratio of organic and inorganic components of dentine, lowering the collagen matrix in mineralized tissues and thus altering its microstructure [ 34 , 35 , 36 ]. Considering these facts of clinical occurrences, especially in immature permanent teeth, they may develop a more brittle and less resistant tooth structure substrate. Subsequently, the endo-treated teeth will be more susceptible to crown or root fractures [ 37 ]. Etidronic acid, also referred to as HEBP (1-hydroxyethylidene-1,1-bisphosphonate) (BP), is a weak, biocompatible chelating solution that has an adequate calcium chelation capacity, is reportedly less abrasive to root dentine than EDTA, and could be utilized in conjunction with NaOCl [ 38 , 39 , 40 , 41 ]. It has the ability to chelate metallic ions. It has been suggested as a potential alternative to EDTA [ 42 ]. The concentration of HEBP is a crucial factor for effective removal of calcium from the root canal as the lower concentrations are less efficient [ 43 ]. Although etidronic acid were tested as an irrigant solutions in a previous study, the effect of compositional alterations of NeoMTA 2 in combination with 5.25% NaOCl and 20% HEBP irrigation protocol on the push-out bond strength has not been reported.

Hence, the aim of this in vitro study was to compare the push-out bond strength of the conventional White MTA cements and the second generation NeoMTA 2 as root end fillings in simulated immature permanent teeth treated with different disinfection protocols, which are 5.25% NaOCl, followed by 17% EDTA, and 5.25% NaOCl, followed by 20% HEBP. The null hypothesis was that there was no significant difference when using 5.25% NaOCl, followed by 17% EDTA, and 5.25% NaOCl, followed by 20% HEBP, among the following two root-end filling materials:

Sample collection

The present experimental study was approved by the Medical Research Ethical Committee (MREC) of the National Research Centre (NRC), Cairo, Egypt (Reference number: 3587062022). All methods were performed in accordance with the Declaration of Helsinki. Forty freshly extracted permanent, straight, single-rooted human teeth were gathered from the oral surgery dental clinic in the National Research Centre, Cairo. Extractions were performed with consent. Teeth were inspected under stereomicroscopy (×10) to eliminate roots with cracks, fractures, and caries. Also, they were radiographed in the mesiodistal and buccolingual aspects to detect any resorption. Exclusion of teeth with decay, cracks, or fractures Teeth were scaled to remove any calcified deposits. Organic tissues and any remaining soft tissue were removed by immersion of the teeth in 5.25% NaOCl for 10 min. Finally, they were stored in distilled water until use.

Specimen size determination

Sample size was determined using sample size calculator software program (G. power 3.19.2) based on research published by Buldur et al., and Shetty et al. [ 44 , 45 ]. Sample size calculation was based on 95% confidence interval and power of 90% with α error of 5%. The minimum sample size estimated for this study was 15 samples in each group.

Samples preparation

The coronal segments of all samples were sectioned by sectioning disc mounted on a low speed handpiece along with water coolant to standardize the teeth lengths at 15 mm. Mechanical preparation was done using ProTaper Next system (files X1- X3) (PTN; Dentsply Maillefer, Ballaigues, Switzerland). The canals were irrigated with 5 mL of freshly prepared 5.25% NaOCl solution, followed by a rinse with 5 ml distilled water.

Root-end preparation and plug condensation

All roots were resected perpendicular to the root’s long axis by a sectioning disc, and 3 mm were removed apically. A balanced force technique was used for apical enlargement until file K-90 (Dentsply/Maillefer, Ballaigues, Switzerland).

The simulated immature roots were arbitrarily divided into four experimental groups ( n  = 15 per group) according to the irrigation protocol and apical plug material as follows:

Group 1 (G1): Samples were irrigated by utilizing 5 ml NaOCl 5.25% (Sigma-Aldrich, Inc., St. Louis, MO, USA), followed by 5 ml 17% EDTA (Sigma-Aldrich, Inc., St. Louis, MO, USA), activated with manual agitation for 5 min., followed by 5 ml distilled water as a final rinse. Canals were slightly dried with paper points and a 5 mm apical plug using White MTA (Pro Root MTA, Dentsply Tulsa Dental, Tulsa, OK, USA) that was prepared according to the manufacturer’s recommendations and incrementally placed in orthograde direction using the MAP system (Roydent, Johnson City, TN, USA) and further compacted with a pre-fitted plugger.

Group 2 (G2): irrigation using 5 ml of 5.25% NaOCl followed by 5 ml of 17% EDTA. Canals were slightly dried using paper points, and an apical plug using Neo MTA 2 (NuSmile Avalon Biomed, Bradenton, FL, USA) was prepared the same way in G1.

Group 3 (G3): irrigation using 5 ml of 5.25% NaOCl along with 5 ml of 20% HEBP (Cublen K8514 GR; Zschimmer & Schwarz, Mohsdorf, Germany) activated manually for 5 min. A 5 mm apical plug using white MTA. Prepared according to the respective manufacturer’s recommendations and incrementally placed in an orthograde direction.

Group 4 (G4): irrigation using 5 ml of 5.25% NaOCl along with 5 ml of EDTA activated manually for 5 min. A 5 mm apical plug using Neo MTA 2. It was prepared and placed as before.

All specimens were labeled and stored in an incubator (CBM, S.r.l. Medical Equipment, 2431/V, Cremona, Italy) at 100% humidity at 37 °C for 48 h to ensure the complete hardening of the tested cements [ 46 , 47 , 48 ]. White MTA and NeoMTA 2, regarding push-out bond strength. The composition of the two root-end filling materials examined in the current study are represented in Table  1 .

Push-out test procedure

The roots apical thirds were sectioned horizontally, perpendicular to their long axis, with a water-cooled precision saw, obtaining a 3 mm (0.1) section in thickness. Sections were gauged by a digital caliper (Pachymeter, Electronic Digital Instruments, China). Each specimen was labeled and pictured coronally and apically using a stereomicroscope (65x) (SZ-PT; Olympus, Tokyo, Japan). A scale was conducted by matching up a ruler of a recognized length using the “Set Scale” tool of the image analysis software (Image J; NIH, Bethesda, MD, USA). The diameter of the filling was measured, and subsequently, the radius was calculated. Every section was mounted in a custom-made loading fixture (a metal block with a circular cavity in the middle). The hole for specimen housing had a central cavity to ease the movement of extruded cement material. A computer-controlled compressive load with a crosshead speed of 1 mm/min on a testing machine (Model 3345; Instron Industrial Products, Norwood, MA, USA) was applied to each specimen.

A load was applied to the specimens’ radicular parts by a plunger of 0.75 mm in diameter. The tip of the plunger was positioned only touching the cement part, avoiding the surrounding dentin, in an apical-coronal direction to avoid any obstruction of the cement movement towards the wider diameter. This guaranteed that during the loading process, the overlaying dentin was efficiently supported.

The maximum load failure (in Newton) was recorded and then converted into MPa. The bond strength was calculated by recording the maximum load and dividing it by the computed surface area, calculated by the following formula [ 40 , 49 ]:

Where; r 1 : apical radius, r 2 : coronal one, h: the thickness of the sample in mm.

The push-out bond strength was determined for each root specimen. Failure was demonstrated by the displacement of the cement out of the canal lumen. The sudden drop in the load-deflection curve confirms bond failure, as recorded by Blue-hill computer software (62.01, version 2.0, NY, USA). Figure  1 represent diagrammatic illustration of the specimen’s preparation.

It provides  the sectioning of the crown and the apical parts.

Statistical analysis

Statistical Package for Social Sciences (SPSS, IBM, Chicago, USA) 16.0 statistical software was used to conduct the statistical study. The normality test carried out by Kolmogrov–Smirnov and Shapiro–Wilk tests; the data exhibited a normal distribution. After utilizing various irrigants, a two-way ANOVA and a Tukey test were used to compare the mean push-out bond strength values (MPa) for the various root-end filling materials. The significance level was set at P  ≤ 0.05.

The mean values and standard deviation of the push-out bond strength (MPa) as function of chelating agent subgroup and different root-end filling materials were outlined in Table 2 .

As regards chelating agents, HEBP showed higher significant push-out bond strength mean values (G3 and G4) than EDTA when used with either White MTA or NeoMTA 2 ( P  = 0.04 and 0.05, respectively) (G1 and G2).

Comparing the two root-end filling materials (White MTA and NeoMTA 2), when EDTA chelating agent was used as an irrigation protocol, there was no significant difference in their bond strength mean values ( P  = 0.85). Similarly, the HEBP chelating agent resulted in an insignificant difference between the bond strength mean values of White MTA and NeoMTA 2 ( P  = 0.73).

Moreover, two-way ANOVA showed that the interaction of variables (Root canal filling type and chelating agent protocol) was not significant ( P  = 0.24). While, the effect of chelating agent protocol separately was significant ( P  = 0.0001), contrary to the effect of type of root canal filling separately was insignificant ( P  = 0.87), as represented in Table 3 .

Achievement of a perfect seal at the apex of immature necrotic teeth and protection of the remaining tooth structure of the immature tooth using a bioinert filling material after efficient root canal debridement are the most important factors for the success of its treatment [ 50 , 51 ].

The management of immature roots is accompanied by many challenges. Its difficulty in debridement of the root canal due to thin roots at risk of fracture and the absence of an apical stop makes root canal filling difficult [ 52 ]. These obstacles can be controlled by enhancing the synthesis of a hard tissue barrier at the root end and augmenting the root against fracture by the apexification technique [ 53 , 54 ]. Several dental materials were used for the formation of the apical barrier, such as calcium hydroxide, freeze-dried dentin, freeze-dried cortical bone, dentin shavings, resorbable ceramic, bone morphogenic protein, MTA, Biodentine, and the recently introduced NeoMTA 2 cement [ 27 , 55 ].

On the other hand, although root canal irrigation is an efficient way for its debridement [ 56 ], it was nevertheless revealed that several chemical irrigants induce alterations in the dentine walls [ 28 ]. The most common and widely applied irrigation protocol includes the use of NaOCl followed by a final flush with EDTA [ 27 , 30 , 42 ]. EDTA is efficient in the removal of the smear layer due to its chelating effect. Though its erosive effect hinders the mechanical characteristics of root dentin by modifying its calcium to phosphorous ratio [ 57 , 58 ], it causes reduction in dentine microhardness, increasing solubility and permeability properties [ 59 , 60 ].

An alternative combination of NaOCl and a weak chelating agent such as etidronic acid (HEBP) has been advocated because it maintains the properties of both individual solutions and decreases the deleterious effect of EDTA on root canal dentine [ 40 , 41 , 59 ]. Yadav et al. was reported that the using of concentration of 18% HEBP was more effective than concentration of 9% HEBP in removing calcium from the root canal due to the higher concentration. [ 43 ].

The adhesion of root-end filling cements to the dentinal walls is one of the significant essentials for success. providing a good root end seal filling material-dentin interface, increasing the ability to pack the root canal filling in the immature roots, and maintaining the integrity of the remaining short, underdeveloped roots [ 61 ]. Nevertheless, the kind of material used for apexification can directly affect the quality of its bonding to the dentin [ 62 ]. In addition to the chemicals used to debride the necrotic, immature, weak permanent teeth [ 63 ]. A root-end filling material should be stable against displacement and dislodging pressures. Push-out bond strength testing is an efficient and reliable way to determine how well a material fits into the surrounding root dentin and how well root-end filling materials resist dislodgement to demonstrate their efficacy [ 64 , 65 , 66 ]. The push-out strength test was conducted after 48 h of material mixing, as it was reported as the most appropriate time to ensure material hardening and the most crucial time to test the bond strength [ 46 , 47 , 48 , 67 , 68 , 69 ].

Consequently, the current study was outlined to evaluate and compare the push-out bond strength of two calcium silicate-based cements used as root end filling materials in simulated immature roots with different irrigation protocols. According to the above findings, the null hypothesis was rejected, as regardless of the apical plug materials used, the type of chelating agent used in disinfection of immature root canals made a significant difference in the push-out bond strength.

Regardless of the apical plug material used, it was observed that when the root canals were treated with 20% HEBP in G3 and G4, they showed greater push-out bond strength mean values than in G1 and G2, where 17% EDTA was used when used following 5.25% NaOCl. This can be referred to as the minimal action of HEBP on dentine physical properties, interfering minimally with the microhardness and roughness of the dentinal walls. Also, it was mentioned in previous studies that HEBP caused the least change in the ability of NaOCl to breakdown organic matter and had the least erosive effect on dentine [ 70 , 71 ]. Therefore, it could be more suitable for disinfection of the canals and dissolving of necrotic tissue in combination with NaOCl without further weakening of the root canal dentine. Furthermore, other studies reported MTA-dentin bond failures after irrigation with NaOCl and EDTA [ 72 , 73 , 74 ]. This may be related to the erosive and dissolving effects of the EDTA chelating agent, rendering dentine weaker for bonding with MTA [ 75 ]. This finding is in accordance with Barrio et al., who showed that irrigation with NaOCl and HEBP after repairing a root canal perforation with calcium silicate-based cements has no detrimental effect on the bond strength of these materials [ 5 ].

The findings of the current study suggest that the treatment of White MTA or Neo MTA 2 with 5.25% NaOCl followed by 20% HEBP solutions provides a stronger bond to the root canal dentine than the treatment with chelating agent to EDTA. Further research is needed to confirm the clinical usage of the suggested irrigation protocol with root end filling materials. Moreover, it is suggested that the irrigant protocol is a significant variable affecting the push-out bond strength more than the type of MTA.

Conclusions

Within the limitations of the current in vitro study, it could be concluded that the combined use of 5.25% NaOCl and 20% HEBP increased the push-out strength values of both White MTA, and NeoMTA 2 rendering them suitable to be used as an alternative chelating agent to EDTA. Moreover, the employed chelating agent within the disinfection protocol had a great influence on the bond strength between dentin and apical plug materials.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Abboud KM, Abu-Seida AM, Hassanien EE, Tawfik HM. Biocompatibility of NeoMTA Plus® versus MTA Angelus as delayed furcation perforation repair materials in a dog model. BMC Oral Health. 2021;21. https://doi.org/10.1186/s12903-021-01552-w .

Kumaravadivel MS, Pradeep S. Recent advancements of endodontic sealers-a review. Int J Pharm Technol. 2016;8:4060–75.

CAS   Google Scholar  

Mahmoud D, Salman R. Effect of different instrument systems on the quality of bio-ceramic obturation material (An in vitro leakage and SEM Study). Erbil Dent J. 2020;3:1–9.

Article   Google Scholar  

Hamdy TM, Galal M, Ismail AG, Abdelraouf RM. Evaluation of flexibility, microstructure and elemental analysis of some contemporary nickel-titanium rotary instruments. Open Access Maced J Med Sci. 2019;7:3647–54.

Article   PubMed   PubMed Central   Google Scholar  

Rebolloso de Barrio E, Pérez-Higueras JJ, García-Barbero E, Gancedo-Caravia L. Effect of exposure to etidronic acid on the bond strength of calcium silicate-based cements after 1 and 21 days: an in vitro study. BMC Oral Health. 2021;21. https://doi.org/10.1186/s12903-021-01959-5 .

Jung IY, Lee SJ, Hargreaves KM. Biologically based treatment of immature permanent teeth with pulpal necrosis: a case series. Tex Dent J. 2012;129:601–16.

PubMed   Google Scholar  

Soares Ade J, Lins FF, Nagata JY, Gomes BP, Zaia AA, Ferraz CC, et al. Pulp revascularization after root canal decontamination with calcium hydroxide and 2% chlorhexidine gel. J Endod. 2013;39:417–20.

Article   PubMed   Google Scholar  

Chan EKM, Desmeules M, Cielecki M, Dabbagh B, Ferraz dos Santos B. Longitudinal Cohort Study of Regenerative Endodontic Treatment for Immature Necrotic Permanent Teeth. J Endod. 2017;43:395–400.

Petrino JA, Boda KK, Shambarger S, Bowles WR, McClanahan SB. Challenges in Regenerative Endodontics: A Case Series. J Endod. 2010;36:536–41.

Nosrat A, Homayounfar N, Oloomi K. Drawbacks and unfavorable outcomes of regenerative endodontic treatments of necrotic immature teeth: A literature review and report of a case. J Endod. 2012;38:1428–34.

Cochrane NJ, Shen P, Yuan Y, et al. Fluoride Varnish: an Evidence-Based Approach. Fluoride. 2012;1:1–15.

Google Scholar  

Rafter M. Apexification: A review. Dent Traumatol. 2005;21:1–8.

Parirokh M, Torabinejad M. Mineral Trioxide Aggregate: A Comprehensive Literature Review-Part III: Clinical Applications, Drawbacks, and Mechanism of Action. J Endod. 2010;36:400–13.

Gandolfi MG, Van Landuyt K, Taddei P, Modena E, Van Meerbeek B, Prati C. Environmental Scanning Electron Microscopy Connected with Energy Dispersive X-ray Analysis and Raman Techniques to Study ProRoot Mineral Trioxide Aggregate and Calcium Silicate Cements in Wet Conditions and in Real Time. J Endod. 2010;36:851–7.

Taddei P, Modena E, Tinti A, Siboni F, Prati C, Gandolfi MG. Vibrational investigation of calcium-silicate cements for endodontics in simulated body fluids. J Mol Struct 2011;993:367–75.

Article   CAS   Google Scholar  

Hamdy TM. Polymers and ceramics biomaterials in Orthopedics and dentistry: A review article. Egypt. J Chem 2018;61:723–30.

Cintra LTA, Benetti F, de Azevedo Queiroz ÍO, de Araújo Lopes JM, Penha de Oliveira SH, Sivieri Araújo G, Gomes-Filho JE. Cytotoxicity, Biocompatibility, and Biomineralization of the New High-plasticity MTA Material. J Endod. 2017;43:774–8.

Rodríguez-Lozano FJ, Lozano A, López-García S, García-Bernal D, Sanz JL, Guerrero-Gironés J, et al. Biomineralization potential and biological properties of a new tantalum oxide (Ta2O5)–containing calcium silicate cement. Clin Oral Investig. 2022;26:1427–41.

Walsh RM, Woodmansey KF, He J, Svoboda KK, Primus CM, Opperman LA. Histology of NeoMTA Plus and Quick-Set2 in Contact with Pulp and Periradicular Tissues in a Canine Model. J Endod. 2018. https://doi.org/10.1016/j.joen.2018.05.001 .

Aktemur Türker S, Uzunoğlu E, Bilgin B. Comparative evaluation of push-out bond strength of Neo MTA Plus with Biodentine and white ProRoot MTA. J Adhes Sci Technol. 2017;31:502–8.

Camilleri J. Staining Potential of Neo MTA Plus, MTA Plus, and Biodentine Used for Pulpotomy Procedures. J Endod. 2015;41:1139–45.

Tomás-Catalá CJ, Collado-González M, García-Bernal D, Oñate-Sánchez RE, Forner L, Llena C, et al. Biocompatibility of New Pulp-capping Materials NeoMTA Plus, MTA Repair HP, and Biodentine on Human Dental Pulp Stem Cells. J Endod. 2018;44:126–32.

Li X, Pedano MS, Li S, Sun Z, Jeanneau C, About I, et al. Preclinical effectiveness of an experimental tricalcium silicate cement on pulpal repair. Mater Sci Eng C. 2020;116:111167.

Zaki DY, Zaazou MH, Khallaf ME, Hamdy TM. In vivo comparative evaluation of periapical healing in response to a calcium silicate and calcium hydroxide based endodontic sealers. Open Access Maced J Med Sci. 2018;6:1475–9.

Bergenholtz G. Micro organisms from necrotic pulp of traumatized teeth. Odont Revy. 1974;25:347–58.

Shuping GB, Ørstavik D, Sigurdsson A, Trope M. Reduction of intracanal bacteria using nickel-titanium rotary instrumentation and various medications. J Endod. 2000;26:751–5.

Article   PubMed   CAS   Google Scholar  

Omar N, Abdelraouf RM, Hamdy TM. Effect of different root canal irrigants on push- out bond strength of two novel root-end filling materials. BMC Oral Health. 2023;23:1–8.

Capar ID, Aydinbelge HA. Surface change of root canal dentin after the use of irrigation activation protocols: Electron microscopy and an energy-dispersive X-ray microanalysis. Microsc Res Tech. 2013;76:893–6.

Siqueira JF, Rôças IN. Clinical Implications and Microbiology of Bacterial Persistence after Treatment Procedures. J. Endod. 2008;34. https://doi.org/10.1016/j.joen.2008.07.028 .

Hamdy TM, Alkabani YM, Ismail AG, Galal MM. Impact of endodontic irrigants on surface roughness of various nickel-titanium rotary endodontic instruments. BMC Oral Health. 2023;23:517.

Article   PubMed   PubMed Central   CAS   Google Scholar  

Cobankara FK, Erdogan H, Hamurcu M. Effects of chelating agents on the mineral content of root canal dentin. Oral Surg Oral Med Oral Pathol Oral Radiol Endodontol. 2011;112. https://doi.org/10.1016/j.tripleo.2011.06.037 .

Qian W, Shen Y, Haapasalo M. Quantitative analysis of the effect of irrigant solution sequences on dentin erosion. J Endod. 2011;37:1437–41.

Hamdy TM, Galal MM, Ismail AG, Saber S. Physicochemical properties of AH plus bioceramic sealer, Bio-C Sealer, and ADseal root canal sealer. Head Face Med. 2024;20:1–9.

Mirseifinejad R, Tabrizizade M, Davari A, Mehravar F. Efficacy of different root canal irrigants on smear layer removal after post space preparation: A scanning electron microscopy evaluation. Iran Endod J. 2017;12:185–90.

PubMed   PubMed Central   CAS   Google Scholar  

Gu LS, Huang XQ, Griffin B, Bergeron BR, Pashley DH, Niu LN, et al. Primum non nocere – The effects of sodium hypochlorite on dentin as used in endodontics. Acta Biomater. 2017;61:144–56.

Pérez-Heredia M, Ferrer-Luque CM, González-Rodríguez MP, Martín-Peinado FJ, González-López S. Decalcifying effect of 15% EDTA, 15% citric acid, 5% phosphoric acid and 2.5% sodium hypochlorite on root canal dentine. Int Endod J. 2008;41:418–23.

Ali MRW, Mustafa M, Bårdsen A, Bletsa A. Fracture resistance of simulated immature teeth treated with a regenerative endodontic protocol. Acta Biomater Odontol Scand. 2019;5:30–37.

Tartari T, Duarte Junior AP, Silva Júnior JOC, Klautau EB, Silva E, Souza Junior MH, et al. Etidronate from medicine to endodontics: Effects of different irrigation regimes on root dentin roughness. J Appl Oral Sci. 2013;21:409–15.

Arias-Moliz MT, Ordinola-Zapata R, Baca P, Ruiz-Linares M, Ferrer-Luque CM. Antimicrobial activity of a sodium hypochlorite/etidronic acid irrigant solution. J Endod. 2014;40:1999–2002.

Zehnder M, Schmidlin P, Sener B, Waltimo T. Chelation in root canal therapy reconsidered. J Endod. 2005;31:817–20.

Kuruvilla A, Jaganath BM, Krishnegowda SC, Ramachandra PKM, Johns DA, Abraham A. A comparative evaluation of smear layer removal by using edta, etidronic acid, and maleic acid as root canal irrigants: An in vitro scanning electron microscopic study. J Conserv Dent. 2015;18:247–51.

Raghavendra Surya, Hindlekar S, Vyavahare A. N. Effect of Etidronic Acid, Chitosan and EDTA on Microhardness of Root Canal Dentin. Saudi J Oral Dent Res. 2018;1300:118–21.

Yadav HK, Tikku AP, Chandra A, Yadav RK, Patel DK. Efficacy of etidronic acid, BioPure MTAD and SmearClear in removing calcium ions from the root canal: An in vitro study. Eur J Dent. 2015;09:523–8.

Buldur B, Öznurhan F, Kaptan A. The effect of different chelating agents on the push-out bond strength of proroot mta and endosequence root repair material. Eur Oral Res. 2019;53:88–93.

Shetty P, Kini S, Ballal NV, Upadhaya N. Effect of chelating agents on shear bond strength of EpoSeal Plus TM sealer to root canal dentin: In vitro study. Saudi Endod J. 2021;11:188–94.

Wang J-S, Bai W, Wang Y, Liang Y-H. Effect of different dentin moisture on the push-out strength of bioceramic root canal sealer. J Dent Sci. 2023;18:129–34.

Guneser MB, Akbulut MB, Eldeniz AU. Effect of various endodontic irrigants on the push-out bond strength of biodentine and conventional root perforation repair materials. J Endod. 2013. https://doi.org/10.1016/j.joen.2012.11.033 .

Vivan RR, Guerreiro-Tanomaru JM, Bosso-Martelo R, Costa BC, Duarte MAH, Tanomaru-Filho M. Push-out bond strength of root-end filling materials. Braz Dent J. 2016. https://doi.org/10.1590/0103-6440201600340 .

Nagas E, Cehreli ZC, Durmaz V, Vallittu PK, Lassila LVJ. Regional Push-out Bond Strength and Coronal Microleakage of Resilon after Different Light-curing Methods. J Endod. 2007;33:1464–8.

García-Godoy F, Loushine RJ, Itthagarun A, Weller RN, Murray PE, Feilzer AJ, et al. Application of biologically-oriented dentin bonding principles to the use of endodontic irrigants. Am J Dent. 2005;18:281–90.

Desai S, Chandler N. The restoration of permanent immature anterior teeth, root filled using MTA: A review. J Dent 2009;37:652–7.

Camp JH, Barrett EJ PF. Pediatric endodontics: endodontic treatment for the primary and young, permanent dentition. CV Mosby Co. 2002;833–9.

Tolibah YA, Kouchaji C, Lazkani T, Ahmad IA, Baghdadi ZD. Comparison of MTA versus Biodentine in Apexification Procedure for Nonvital Immature First Permanent Molars: A Randomized Clinical Trial. Children. 2022;9. https://doi.org/10.3390/children9030410 .

Zaki DY, Zaazou MH, Khallaf ME, Hamdy TM. In Vivo Comparative Evaluation of Periapical Healing in Response to a Calcium Silicate and Calcium Hydroxide Based Endodontic Sealers. Open Access Maced J Med Sci. 2018;6:1–5.

Zeid STA, Alamoudi NM, Khafagi MG, Abou Neel EA. Chemistry and Bioactivity of NeoMTA Plus TM versus MTA Angelus® Root Repair Materials. J Spectrosc. 2017;2017. https://doi.org/10.1155/2017/8736428 .

Ali A, Bhosale A, Pawar S, Kakti A, Bichpuriya A, Agwan MA Current Trends in Root Canal Irrigation. Cureus 2022. https://doi.org/10.7759/cureus.24833 .

Haapasalo M, Shen Y, Qian W, Gao Y. Irrigation in Endodontics. Dent Clin North Am. 2010;54:291–312.

Zehnder M. Root Canal Irrigants. J Endod. 2006;32:389–98.

Uzunoglu E, Aktemur S, Uyanik MO, Durmaz V, Nagas E. Effect of ethylenediaminetetraacetic acid on root fracture with respect to concentration at different time exposures. J Endod. 2012;38:1110–3.

Çalt S, Serper A. Time-dependent effects of EDTA on dentin structures. J Endod. 2002;28:17–19.

Cimpean SI, Burtea ALC, Chiorean RS et al. Evaluation of Bond Strength of Four Different Root Canal Sealers. Materials. 2022;15. https://doi.org/10.3390/ma15144966 .

Guerrero F, Mendoza A, Ribas D, Aspiazu K. Apexification: A systematic review. J Conserv Dent. 2018;21:462–5.

Elbahary S, Haj-yahya S, Khawalid M et al. Effects of different irrigation protocols on dentin surfaces as revealed through quantitative 3D surface texture analysis. Sci Rep. 2020;10. https://doi.org/10.1038/s41598-020-79003-9 .

Donnermeyer D, Dornseifer P, Schäfer E, Dammaschke T. The push-out bond strength of calcium silicate-based endodontic sealers. Head Face Med. 2018;14:1–7.

Topçuoʇlu HS, Arslan H, Akçay M, Saygili G, Çakici F, Topçuoʇlu G. The effect of medicaments used in endodontic regeneration technique on the dislocation resistance of mineral trioxide aggregate to root canal dentin. J Endod. 2014;40:2041–4.

Majeed A, Alshwaimi E. Push-Out Bond Strength and Surface Microhardness of Calcium Silicate-Based Biomaterials: An in vitro Study. Med Princ Pr. 2017;26:139–45.

Tomer AK, Dayal C, Malik N, Bhardwaj G, Muni S, Sharma A. An in vitro Evaluation of the Push-out Bond Strength of Biodentine and MTA Plus Root Perforation Repair Materials after Irrigation with Different Endodontic Irrigants. Int J Oral Care Res. 2016;4:53–57.

Alcalde MP, Vivan RR, Marciano MA et al. Effect of ultrasonic agitation on push-out bond strength and adaptation of root-end filling materials. Restor Dent Endod. 2018;43. https://doi.org/10.5395/rde.2018.43.e23 .

Alsubait SA. Effect of sodium hypochlorite on push-out bond strength of four calcium silicate-based endodontic materials when used for repairing perforations on human dentin: An in vitro evaluation. J Contemp Dent Pr. 2017;18:289–94.

Tartari T, Guimarães BM, Amoras LS, Duarte MAH, Silva e Souza PAR, Bramante CM. Etidronate causes minimal changes in the ability of sodium hypochlorite to dissolve organic matter. Int Endod J. 2015;48:399–404.

Girard S, Paqué F, Badertscher M, Sener B, Zehnder M. Assessment of a gel-type chelating preparation containing 1-hydroxyethylidene-1, 1-bisphosphonate. Int Endod J. 2005;38:810–6.

Kogan P, He J, Glickman GN, Watanabe I. The Effects of Various Additives on Setting Properties of MTA. J Endod. 2006;32:569–72.

Lee YL, Lin FH, Wang WH, Ritchie HH, Lan WH, Lin CP. Effects of EDTA on the hydration mechanism of mineral trioxide aggregate. J Dent Res. 2007;86:534–8.

Nagas E, Cehreli ZC, Uyanik MO, Durmaz V, Vallittu PK, Lassila LVJ. Bond strength of mineral trioxide aggregate to root dentin after exposure to different irrigation solutions. Dent Traumatol. 2014;30:246–9.

Smith JB, Loushine RJ, Weller RN, Rueggeberg FA, Whitford GM, Pashley DH, Tay FR. Metrologic Evaluation of the Surface of White MTA After the Use of Two Endodontic Irrigants. J Endod. 2007;33:463–7.

Download references

Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB).

Author information

Authors and affiliations.

Restorative and Dental Materials Department, Oral and Dental Research Institute, National Research Centre (NRC), Giza, Dokki, 12622, Egypt

Nada Omar & Tamer M. Hamdy

Pediatric Dentistry Department, Faculty of Dentistry, Misr University for Science and Technology (MUST), Cairo, Egypt

Nihal Refaat Kabel

Dental Biomaterials Department, Faculty of Dental Medicine, Boys, Al Azhar University, Cairo, Egypt

Muhammad Abbass Masoud

You can also search for this author in PubMed   Google Scholar

Contributions

Nada Omar conceived the ideas; Nada Omar, Nihal Refaat Kabel, and Muhammad Abbass Masoud designed the study. Nada Omar, Nihal Refaat Kabel, Muhammad Abbass Masoud, and Tamer M. Hamdy collected and analyzed the data. Tamer M. Hamdy checked the data and revised the manuscript. Nada Omar, Nihal Refaat Kabel, and Tamer M. Hamdy wrote the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Tamer M. Hamdy .

Ethics declarations

Competing interests.

The authors declare no competing interests. This in vitro study received ethical approval from the Medical Research Ethical Committee (MREC) of the National Research Centre (NRC), Cairo, Egypt (Reference number: 3911911022). All methods were carried out in accordance with relevant guidelines and regulations. This study was carried out in accordance with the Declaration of Helsinki. Extractions were performed with consent.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

Omar, N., Kabel, N.R., Masoud, M.A. et al. Impact of different disinfection protocols on the bond strength of NeoMTA 2 bioceramic sealer used as a root canal apical plug (in vitro study). BDJ Open 10 , 75 (2024). https://doi.org/10.1038/s41405-024-00257-w

Download citation

Received : 24 May 2024

Revised : 05 August 2024

Accepted : 11 August 2024

Published : 23 September 2024

DOI : https://doi.org/10.1038/s41405-024-00257-w

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

The influence of El Niño on springtime synoptic-scale precipitation extremes in Southeastern China: insights from CMIP6 model simulations

• Original Article
• Open access
• Published: 24 September 2024

Cite this article

You have full access to this open access article

• Dingrui Cao 1 , 2 ,
• Chi-Yung Tam   ORCID: orcid.org/0000-0002-5462-6880 1 , 2 &
• Kang Xu 3  

1 Altmetric

This study focuses on El Niño impacts on springtime extreme precipitation in Southeastern China (SEC) by comparing observations with data from the Coupled Model Intercomparison Project phase 6 (CMIP6) historical runs. Observational and simulated results suggest that synoptic-scale temperature advection patterns over East Asia (EA) are closely associated with extreme precipitation in SEC, encompassing the Pearl River Basin (PRB), Yangtze River Basin (YRB), and Huaihe River Basin (HRB). Based on this, we introduce a temperature advection index (TAI) tailored to capture the cold-warm temperature advection dipole, which shows a significant positive correlation with SEC precipitation. Both observations and CMIP6 indicate that TAI-related circulations, characterized by upper-level synoptic-scale waves and a north–south oriented temperature gradient over EA, are conducive to extreme precipitation in northern PRB (NPRB)–YRB–HRB. However, the TAI-related synoptic-scale activities have a lesser impact on extreme precipitation in southern PRB (SPRB), as these disturbances mainly affect the mid-latitude weather. Further investigation reveals that during boreal spring following El Niño, 85% of extreme events in YRB–HRB are associated with positive TAI values, compared to 76% under climatological conditions. However, such a change in the association with TAI is not evident in CMIP6 simulations. From observations, atmospheric baroclinicity along the East Asian westerly jet is enhanced during El Niño, which promotes the development of TAI-related synoptic-scale disturbances. In contrast, CMIP6 models struggle to reproduce these observed baroclinicity signals during El Niño. This challenge arises from the background westerly jet bias and mean-state cold tongue bias in tropical Pacific temperature in models.

Avoid common mistakes on your manuscript.

1 Introduction

China is located in the East Asian monsoon region, where the climate is heavily influenced by monsoon circulations (Gao et al. 2014 ; Li et al. 2019a , b ; Xue et al. 2023 ). Spring is the transition season from winter to summer monsoon (Yang et al. 2021 ; Wu et al. 2023 ). During this period, cold air from the mid-high latitudes and warm, moist air from the lower latitudes usually converge in Southeastern China (SEC), forming frontal systems that contribute to heavy rainfall in SEC (Wang et al. 2021b ; Li et al. 2022 ). Previous studies indicated that various external forcing factors can affect the interannual variability of spring precipitation in China (Jia et al. 2018 , 2021 ; Li et al. 2021a ; Zhu et al. 2022 ). El Niño–Southern Oscillation is the most prominent interannual variability in the tropical air–sea coupling system, exerting a significant influence on the climate and extreme weather in SEC from its development phase to its decay phase through atmospheric teleconnections (Lau 1992 ; Wang et al. 2000 ; Wang and Zhang 2002 ; Kim and Kug 2018 ; Wu et al. 2024 ). El Niño significantly influences extreme precipitation in SEC. In boreal spring, heavy rainfall tends to concentrate in southern China, presenting significant threats to society, economy, and ecosystems (Feng et al. 2011 ; Zhou et al. 2019 ; Gao and Li 2023 ; Zhong et al. 2023 ). Consequently, it becomes imperative to implement effective flood and disaster prevention measures during El Niño.

Many studies indicate the anomalous SEC springtime precipitation in relation to El Niño (Feng et al. 2011 ; Wang et al. 2019 , a ; Li et al. 2021b ; Jing and Sun 2023 ). El Niño events commonly induce a lower-level Western North Pacific anomalous anticyclone (WNPAC), which forms in boreal fall and remains prominent throughout winter and into the decaying spring (Wang et al. 2000 ; Wu et al. 2003 ). On the northwestern flank of the WNPAC, southwestward airflow can transport ample water vapor to the SEC region, leading to heavy precipitation in SEC (Wang et al. 2019 ; Li et al. 2021b ). Gao et al. ( 2022 ) further demonstrates that El Niño influence on springtime extreme rainfall in China is several times greater than its impact on the seasonal mean rainfall. Springtime SEC extreme rainfall has significant interannual variability, and at the same time is also influenced by synoptic-scale activities (Qin et al. 2017 ; Zhang and Meng 2018 ; Chan et al. 2020 ; Jiang et al. 2020 ; Xu et al. 2022 ). Qin et al. ( 2017 ) showed that cyclone activities are a significant contributor to heavy springtime rainfall events in the Yangtze River basin–Huaihe River valleys region, serving as a crucial indicator for extreme precipitation. Zhang and Meng ( 2018 ) found that mid-level troughs and low-level vortices are significant weather processes influencing a severe rainstorm event in Guangdong province in March 2014. SEC heavy springtime rainfall is also associated with intense frontal activity, which is attributed to the confluence of cold and warm air (Hayasaki and Kawamura 2012 ; Wang et al. 2021b ; Xu et al. 2022 ). Therefore, SEC springtime precipitation and extremes are influenced by circulation elements at a variety of scales.

Previous works also examine the performance of general circulation models (GCMs) in simulating springtime SEC precipitation (Zhang et al. 2013 ; Ai et al. 2022 , 2023 ), as well as the influence of El Niño (Wu and Mao 2016 ; Wang et al. 2019 ; Li et al. 2021b ; An et al. 2023 ). Models tends to underestimate precipitation along the southeastern coastal areas of China, consistent with bias in vertical moisture advection (Dong and Dong 2021 ; Chen et al. 2021 ). Still, GCMs can capture the general trend of decreasing precipitation from southeast to northwest over the SEC region. Also, GCMs can effectively replicate the pronounced moisture divergence over Northwestern Pacific (WNP) and the increased precipitation over SEC, in relation to anomalous WNPAC during El Niño in the subsequent spring season (Wang et al. 2019 , 2021a ; Li et al. 2021b ).

El Niño influences extreme precipitation over SEC by modulating the seasonal mean circulation (Gao et al. 2020 ; Cao et al. 2024 ). However, there has been limited research on how El Niño affects synoptic-scale activities related to extreme precipitation. Our study primely address this research gap and we pose three key questions: By using observations and the Coupled Model Intercomparison Project phase 6 (CMIP6) historical runs, we explore (1) synoptic-scale disturbances associated with springtime extreme precipitation over SEC; (2) how El Niño influences these phenomena; (3) whether CMIP6 models accurately simulate the climatological SEC extreme precipitation and El Niño-related variations, along with the associated dynamic processes.

2 Data, methodology and model

2.1 observational and model datasets.

This study utilizes (1) Global monthly SST at a horizontal resolution of 1° × 1°, obtained from the Hadley Centre Global Sea Ice and Sea Surface Temperature analysis dataset (HadISST version 1.1; Rayner et al. 2003 ), (2) Reanalysis data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) (Kalnay et al. 1996 ), encompassing monthly (daily) three-dimensional wind, geopotential height, specific humidity, and temperature data from 1000 to 10 hPa, with a vertical resolution of 17 pressure levels at 2.5° × 2.5°, and (3) Precipitation data at a resolution of 0.25° × 0.25° obtained from the Asia Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation (APHRODITE version 1101 and APHRODITE V1101EX_R1; Yatagai et al. 2012 ). These datasets cover the analysis period from 1951 to 2015, and anomalies are calculated as deviations from the climatological values.

To evaluate the performance of CMIP6 models, we collected and assessed daily atmospheric variables along with monthly SST from the historical runs of 20 coupled models spanning the period from 1951 to 2014. Table 1 provides the relevant information regarding the model experiments. Given the limited availability of multiple realizations in the models, we have exclusively utilized the first realization (r1i1p1f1) from each model. Before conducting our analyses, the outputs from each model were interpolated onto the same spatial grid as the observational data.

2.2 Methodology

2.2.1 identification of el niño events.

The Niño 3.4 index, defined as the area-averaged SST anomalies over the equatorial central-eastern Pacific (5°S–5°N, 170°W–120°W), is used for identifying El Niño events in both observations and models (Trenberth 1997 ; Fredriksen et al. 2020 ; Van Oldenborgh et al. 2021 ). Prior to calculating the index, SST fields were detrended and bandpass filtered to preserve variations with periods less than 7 years, thereby retaining interannual SST variability across the tropics. An El Niño event is identified whenever the December-to-February (DJF) standardized Niño 3.4 index exceeds the values of 0.8. All models can simulate the observed-like warming SST signals in the tropical central-eastern Pacific during El Niño in mature boreal winter (Fig. S1 ).

2.2.2 Model selection

Previous studies demonstrated the presence of a significant WNPAC during El Niño, accompanied by moisture flux divergence over WNP and convergence over SEC (Wang et al. 2000 , 2019 ; Wu et al. 2003 ). Associated with these circulation features are intense precipitation in SEC (Gao et al. 2020 ; Cao et al. 2024 ). To identify models capable of representing such seasonal mean circulations, we analyze the anomalous moisture flux transport vertically integrated from the surface to 300 hPa, weighted by mass, during El Niño in the subsequent spring, using both observations and 20 models. Then, spatial correlation coefficients are computed for the vertically integrated moisture flux divergence over the region of 105°E–150°E; 5°N–30°N (see blue box in Fig. S2a) between observations and each model. Results show that spatial correlation coefficients range from 0.02 to 0.88 among the 20 models. A spatial correlation coefficient threshold of 0.6, derived by averaging the spatial correlation coefficients from the 20 models, is used to select models capable of replicating the moisture transport pattern. Finally, 13 models meeting the aforementioned criteria are selected (indicated by the red hollow circles in Fig. S3 and also highlighted in boldface font in Table  1 ), as these models are able to capture the WNPAC and moisture transport effectively. The remaining 7 models (indicated by the black hollow circles in Fig. S3) fail to simulate such circulations during El Niño, and the reasons for this are detailed in the supplementary materials (see details in S1).

2.2.3 Definition of extreme precipitation events

Extreme precipitation events are identified by applying a threshold set at the 95th percentile of all days in March–April-May (MAM) with precipitation exceeding 0.1 mm. Here, we define a wet day as any day with daily rainfall exceeding 0.1 mm. When daily rainfall surpasses this threshold, it is classified as an extreme precipitation event (Lui et al. 2019 ; Kim et al. 2019 ).

2.2.4 Wave activity flux analysis for stationary Rossby waves

Wave activity flux is widely used to depict Rossby wave dispersion induced by oceanic and land forcing factors (Kosaka and Nakamura 2006 ; Liu et al. 2014 ; Feng et al. 2017 ). In this study, the wave activity flux ( \(W\) ) for investigating stationary Rossby waves induced by El Niño is expressed as follows (Takaya and Nakamura 2001 ):

where \(a\) is earth radius; \(\overrightarrow{U}=\left(U, V\right)\) is basic state wind velocity; φ and \(\uplambda\) represent latitude and longitude, respectively; \({\varPsi }^{\prime}\) and \(p\) donate the perturbation geostrophic stream-function and pressure scaled by 1000 hPa, respectively.

2.2.5 Stationary wavenumber

Previous studies have emphasized the critical role of the background westerlies in the propagation of stationary Rossby waves (Hoskins and Karoly 1981 ; Hoskins and Ambrizzi 1993 ). The stationary wavenumber ( \(Ks\) ), which acts as a refractive index for Rossby waves and identifies regions serving as waveguides with maximum \(Ks\) values, is calculated as described by Hoskins and Ambrizzi ( 1993 ):

where \(\overline{U }\) indicates climatology of zonal winds; \(\varphi\) is the latitude; \(a\) and \(\Omega\) donate the equatorial Earth radius and Earth’s rotation rate, respectively.

2.2.6 Eady growth rate

The atmospheric baroclinic instability over EA contributes to the storm track activity (Lee 2000 ; Chang and Fu 2002 ; Liao et al. 2018 ) and is an important cause of strong precipitation (Qin et al. 2017 ). Eady growth rate ( \(EGR\) ), an effective measure of atmospheric baroclinic instability (Lindzen and Farrell 1980 ), is defined as:

where \(f\) is the Coriolis parameter, \(N\) is the Brunt–Väisälä frequency (where \({N}^{2}=\frac{g}{\theta }\frac{\partial \theta }{\partial z}\) , \(g\) being the acceleration due to gravity, \(z\) is the vertical coordinate, and \(\theta\) is the potential temperature), \(u(z)\) is the vertical profile of the eastward wind component.

2.2.7 Temperature advection

In spring, frontal synoptic conditions make significant contributions to persistent heavy rainfall in SEC. The prominent characteristic of such weather systems is the convergence of warm and cold air masses in the SEC region due to the substantial north–south oriented temperature gradient (Sawyer and Sutton 1997 ; Grotjahn 2003 ). To uncover the connection between these systems and extreme rainfall events in SEC, we calculate the horizontal temperature advection:

where the \(\frac{\partial T}{\partial x}\) and \(\frac{\partial T}{\partial y}\) are zonal and meridional temperature gradients, \(u\) and \(v\) are zonal and meridional wind, respectively.

2.2.8 Moisture budge analysis

Moisture budget analysis is utilized to delineate the underlying physical processes related to extreme precipitation during El Niño. The moisture budget is expressed as follows (Palmén and Newton 1969 ; Tan et al. 2022 ):

where \(P\) and \(E\) indicate precipitation rate and evaporation rate from the surface, respectively; \(\frac{\partial W}{\partial t}\) and \(\nabla \cdot \overrightarrow{Q}\) are the local rate of changes in water vapor ( \(W\) ) and moisture flux ( \(\overrightarrow{Q}\) ) divergence, respectively.

Here, our primary focus is on interannual-scale moisture transport anomalies induced by El Niño events. Since the regional precipitation is roughly balanced between local evaporation and remote moisture transport on a seasonal mean timescale (Brubaker et al. 1993 ; Li et al. 2013 ; Wang et al. 2017 ), \(\frac{\partial W}{\partial t}\) can be ignored. Hence, the moisture budget can be further represented as:

The moisture flux ( \(\overrightarrow{Q}\) ), integrated in pressure coordinates from the surface to upper-level pressure, are expressed as follows (Peixto and Oort 1984 ):

where the \(g\) is the gravitational acceleration, \(\overrightarrow{V}=(u,v)\) is the horizontal wind vector, \(q\) is the specific humidity, \({\rho }_{w}\) is the density of water, \({p}_{t}\) is the upper-level pressure (300 hPa), and the \({p}_{s}\) is the surface pressure. \(\nabla \cdot \overrightarrow{\text{Q}}>0\) denotes the divergence of moisture flux, and \(\nabla \cdot \overrightarrow{\text{Q}}<0\) denotes the convergence of moisture flux.

3 El Niño impacts on SEC extreme precipitation

We first investigate how El Niño affects SEC precipitation in the following spring, using observations and models identified in Sect.  2.2.2 . During El Niño, both observations (Fig.  1 a–c) and the multi-model ensemble (MME) mean (Fig.  1 d–f) indicate an increase in seasonal total precipitation (Fig.  1 a, d), total accumulated extreme precipitation (Fig.  1 b, e), and frequency of extremes (Fig.  1 c, f) over SEC, including Pearl River Basin (PRB), Yangtze River Basin (YRB), and Huaihe River Basin (HRB) subregions. In fact, both datasets indicate significant contributions of the extreme (Fig.  1 b, e) to the total precipitation (Fig.  1 a, d), as suggested by their similar patterns, highlighting the importance of extreme precipitation during El Niño. Additionally, both observations and MME indicate that El Niño events contribute not only to the increased intensity of SEC extreme precipitation in the following spring but also to its increased frequency (Fig.  1 c, f). Previously it was shown that the WNPAC is a significant factor causing moisture flux divergence or convergence over East Asia (EA)–WNP during El Niño. Results from observations (Fig.  2 a) and MME (Fig.  2 b) indicate that such an anticyclone acts to transport warm and moist air from low latitudes to the SEC, resulting in above-average precipitation in this region.

Precipitation anomalies during the following spring of El Niño based on a – c APHRODITE and d – f MME mean of 13 selected models. a , d total accumulated seasonal precipitation (shading; mm season −1 ), b , e total accumulated extreme precipitation (shading; mm season −1 ), c , f frequency of extreme precipitation (shading: day season −1 ). Black dots for a – c indicate the signals passing the 90% significance level. Black dots for d – f indicate locations over which more than 80% of models agree on the sign of precipitation anomalies between MME and each model

Anomalous vertically integrated moisture flux (vectors; kg m −1  s −1 ) and its divergence (shading; mm day −1 ) during the following spring of El Niño based on a NCEP and b MME mean of 13 models. Only moisture flux anomalies > 10 kg m −1  s −1 are shown. Purple crosses in a indicate that moisture flux divergence anomalies pass the 90% significance level, and those in b indicate locations over which more than 80% of models agree on the sign of moisture flux divergence anomalies between MME and each model

4 Temperature advection index (TAI)

In addition to the WNPAC, which is the primary seasonal mean feature influencing SEC during El Niño, synoptic-scale activities also affect SEC precipitation extremes (Chan et al. 2020 ; Cao et al. 2024 ). Previous studies showed that in spring, the confluence of cold and warm air masses over SEC significantly contributes to heavy rainfall in the region (Wang et al. 2021b ; Li et al. 2022 ). Therefore, we attempt to use daily temperature advection to quantify its relationship with extreme precipitation in SEC. To do this, we examine temperature advection anomalies during MAM by comparing SEC extreme precipitation days with climatological conditions. We calculate daily SEC rainfall by averaging rainfall over 112°E–122°E and 22°N–34°N (see red box in Fig.  1 a). The temperature advection fields are initially detrended to eliminate long-term variations caused by global warming effects. Both observations (Fig.  3 a, b) and MME mean (Fig.  3 c, d) indicate that the confluence of cold and warm temperature advection over SEC (TA pattern, hereafter) signifies active frontal synoptic conditions, conducive to occurrence of extreme precipitation in the area. This convergence structure extends from the lower troposphere to the mid-troposphere, representing a vertically extensive frontal system. Here, we analyze synoptic-scale features linked to extreme precipitation over SEC using daily temperature advection.

Horizontal temperature advection anomalies (shading; ℃ day −1 ) and its zonal and meridional vector components (vector; ℃ day −1 ) at a , c 850 hPa and b , d 500 hPa, associated with extreme precipitation days in MAM over SEC based on a , b NCEP reanalysis data and c , d MME mean of 13 models; Purple crosses in a , b indicate temperature advection anomalies passing the 99% significance level, while those in c , d represent locations where more than 80% of models agree on the sign of temperature advection anomalies between MME and each individual model. Only vectors with magnitudes greater than 0.5 ℃ day −1 are shown

Following this, we performed EOF analyses on the 850 hPa daily temperature advection within the region of 105°E–135°E and 17.5°N–40°N (outlined by the red box in Fig.  3 a). In observations, the first leading EOF mode (EOF1), which explains 26.3% of the EA domain-temperature advection variability on the synoptic timescale, represents a typical monopole temperature advection pattern (see Fig. S4a). The EOF1 mode is not the focus of this study and will, therefore, not be discussed further. The second leading EOF mode (EOF2), with an explained variance of 18.7%, is characterized by a dipole temperature advection pattern (hereafter referred to as the EOF2 TA pattern), closely resembling the TA pattern during extreme precipitation events in SEC, albeit with a slight northward shift (Fig.  4 a). These findings suggest a close relationship between EOF2 of daily temperature advection and SEC precipitation. In models, the EOF1 and EOF2 modes of daily temperature advection (see Figs. S5 and S6) and their corresponding explained variance ratios (Table S1 ) are provided in the supplemental materials. Here, we introduce a normalized principal component for EOF2, termed the temperature advection index (TAI), with the aim of quantifying synoptic-scale disturbances related to SEC precipitation (Fig.  4 b). Note that TAI derived from daily temperature advection at 850 hPa, 700 hPa, and 500 hPa exhibit high correlation with each other, and the results obtained from utilizing TAI at each of these levels in subsequent studies are consistent.

EOF2 of daily temperature advection (shading; ℃ day −1 ) over the region 17.5°N–40°N, 105°E–135°E at 850 hPa and a TAI time series obtained from the EOF2 of daily temperature advection based on NCEP reanalysis data; The x-axis in b represents the time series for the spring seasons from 1951 to 2014, totaling 5888 days; the y-axis in b represents the daily TAI values. The red (blue) line in b represents TAI values greater (less) than zero

To examine the relationship between TAI and SEC precipitation, we regress TAI onto the daily precipitation data. Observations reveal positive rainfall anomalies in most provinces of the SEC region, spanning latitudes 24°N–35°N, including the YRB, northern PRB (NPRB), and HRB (Fig.  5 a). However, the impact of synoptic-scale activities represented by TAI on rainfall in southern PRB (SPRB) is relatively small, consistent with the more northward displacement of EOF2 (Fig.  4 a) compared to the TA pattern during SEC extreme precipitation events (Fig.  3 ). As a result, TAI-induced circulations can only depict mid-latitude disturbances, with minimal influence on weather conditions in SPRB. Most models can replicate the observed TAI-induced precipitation pattern (referred to as the TAI-rainfall pattern), although some models (i.e., ACCESS-CM2, GFDL-CM4, MRI-ESM2-0) exhibit a noticeable southward shift in this pattern (Fig. S8). This shift is characterized by underestimated YRB–HRB, and overestimated PRB precipitation. Such discrepancies result from a southward shift bias in the EOF2 TA pattern within these models (Fig. S6). To identify models capable of accurately representing the relationship between TAI and precipitation over SEC, we compute spatial correlation coefficients between the observed TAI-rainfall pattern and that from 13 models, within the region of 20°N–40°N; 110°E–125°E. 10 models are able to reasonably simulate the TAI-rainfall pattern, with spatial correlation coefficients all exceeding 0.7 (see red hollow circles in Fig. S9). Three models (ACCESS-CM2, GFDL-CM4, MRI-ESM2-0) exhibit significantly lower spatial correlation coefficients compared to the other models (see black hollow circles in Fig. S9). These three models erroneously give negative precipitation anomalies over YRB–HRB (Fig. S8). In the end, 10 models (well-performing models, hereafter) possess good capabilities in simulating the TAI-rainfall pattern. These well-performing models will be utilized to investigate how El Niño modulates weather activities associated with extreme precipitation.

Anomalies of March–May daily precipitation (shading; mm day −1 ) obtained by regressing onto TAI in a , d climatological and b , e El Niño sense, and c , f the difference between the latter and the former based on a – c APHRODITE data and d – f MME mean of well-performing models. The black dots in a , b indicate precipitation anomalies passing the 99% significance level, and the black dots in d , e indicate locations over which more than 80% of models agree on the sign of anomalies of precipitation anomalies between MME and each of model

We further investigate the relationship between TAI and daily rainfall/extreme rainfall over NPRB–YRB–HRB in both observations and well-performing models. Both observations and well-performing models indicate a strong linear correlation between TAI and daily rainfall (Table S2). However, such a strong linear correlation is not found between TAI and extreme rainfall events (Table S2). The above results indicate that the synoptic-scale disturbances represented by TAI have a strong linear influence on daily rainfall in NPRB–YRB–HRB, with positive (negative) TAI-related circulations favoring positive (negative) anomalies of daily rainfall in these regions. Although the linear correlation between TAI and extreme rainfall events is not significant, most extreme rainfall events occur under circulations represented by positive TAI (see Fig. S10). This suggests that the influence of TAI-related circulations on extreme rainfall events is a nonlinear process. Specifically, the weather processes leading to very intense extreme rainfall events (i.e., heavy rainfall nearly doubling the 95th percentile threshold, as shown in Fig. S10) are complex and do not solely depend on TAI-related synoptic-scale disturbances. However, it is noteworthy that, compared with climatology, circulations represented by positive TAI significantly increase the probability of extreme rainfall events in the NPRB–YRB–HRB region (Table S3). Thus, TAI has predictive significance for the probability of extreme rainfall events in NPRB–YRB–HRB, although its linear relationship with the intensity of extreme rainfall is relatively weak.

5 Changes in TAI-induced synoptic-scale activities during El Niño

Next, we compare rainfall anomalies regressed onto all-day TAI (climatological sense, hereafter, see Fig.  5 a, d) with those regressed onto all-day TAI during El Niño (El Niño sense, hereafter, see Fig.  5 b, e). From observations, although TAI-rainfall pattern in climatological sense and El Niño sense shares an identical pattern (Fig.  5 a, b), differences exist between the former and the latter. To be specific, in El Niño sense, precipitation over the YRB–HRB region (110°E–125°E; 27°N–34°N; see red box in Fig.  5 c) increases compared to that for climatological sense, indicating that El Niño events can enhance precipitation over YRB–HRB. Note that there is almost no precipitation change attributed to synoptic-scale activities over PRB during El Niño (Fig.  5 c). This is primarily because precipitation in the PRB region is mainly influenced by WNPAC during El Niño, while it is less affected by mid-latitude synoptic-scale disturbances represented by TAI. Although the MME mean of well-performing models generally replicates the TAI-rainfall pattern both in the climatological and El Niño sense (Fig.  5 d, e), it fails to capture the distinction between these two senses (Fig.  5 f).

The above suggests that El Niño may promote synoptic-scale activities represented by TAI, leading to increased extreme precipitation over YRB–HRB. However, models fail to capture this phenomenon. To validate these findings, we initially investigate the disparity between TAI in climatological sense and that in El Niño sense using a Z test on both observational data and well-performing models (Table  2 ). It is worth noting that we chose the Z test because TAI values in both climatological sense and El Niño sense are based on large sample sizes of over a thousand data points. Observations reveal a significant positive TAI with a P value below 0.05. On the other hand, most well-performing models struggle to capture this change in El Niño sense. Only two models, CESM2-FV2 and MPI-ESM1-2-HR, successfully distinguish such a difference. This outcome indicates while El Niño is observed to enhance the occurrence of circulations represented by TAI, such a feature is not adequately captured by most well-performing models.

To quantify the relationship between TAI and extreme precipitation over YRB–HRB, we introduce the concept of TAI-induced extreme precipitation ratio (hereafter referred to as TAI-extreme ratio), defined as the ratio of the number of YRB–HRB extreme precipitation events with positive TAI to the total number of YRB–HRB extreme precipitation events. A higher TAI-extreme ratio indicates a greater influence of synoptic-scale activities represented by TAI on extreme precipitation. Daily precipitation over YRB–HRB (as delineated by the red box in Fig.  5 c) is computed by averaging precipitation over the area of 110°E–125°E; 27°N–34°N. The 95th percentile of the daily region-averaged precipitation over YRB–HRB serves as the threshold for identifying extreme events. Extreme precipitation events in YRB–HRB associated with positive TAI are abbreviated as TAI-extremes.

We also compare the TAI-extreme ratio in El Niño sense (El Niño-TAI-extreme ratio, hereafter) with the TAI-extreme ratio in climatological sense (Clim-TAI-extreme ratio, hereafter). Table 3 presents El Niño-TAI-extreme ratios and Clim-TAI-extreme ratios, utilizing observations, MME mean of well-performing models, as well as those from CESM2-FV2 and MPI-ESM1-2-HR. The observed El Niño-TAI-extreme ratio (0.85) notably exceeds the Clim-TAI-extreme ratio (0.76), affirming that El Niño can foster conducive conditions for TAI-extremes. Conversely, no difference is noted between El Niño-TAI-extreme and Clim-TAI-extreme ratios in the MME mean, both being 0.65. Among the 10 well-performing models, a notable difference is found between TAI in the climatological sense and El Niño sense in CESM2-FV2 and MPI-ESM1-2-HR, which warrants further investigation. In these two models, only minor differences are noted between El Niño-TAI-extreme and Clim-TAI-extreme ratios. While CESM2-FV2 and MPI-ESM1-2-HR effectively capture significantly positive TAI during El Niño, they fall short in reproducing changes in TAI-extremes during El Niño.

The above results indicate that in observations, El Niño events significantly increase the frequency of TAI-related rainfall events, while well-performing models fail to capture this phenomenon. Here, we need to verify whether there is a close relationship between TAI and YRB–HRB daily rainfall. We define daily rainfall events occurring when TAI values are positive as “rainfall in the TAI sense” and all rainfall events during wet days as “rainfall in the climatological sense.” Figure S11 shows both observed and simulated probability density function (PDF) distributions of daily precipitation for the YRB–HRB region in the climatological sense (blue curve) and the TAI sense (red curve). The vertical red (blue) lines in Fig. S11 indicate the 95th percentile of daily rainfall in the TAI (climatological) sense. Both observations and well-performing models show a lower peak value in their daily rainfall PDFs and a more right-skewed distribution in the TAI sense compared with the climatological sense. More importantly, in both observations and well-performing models, the 95th percentile of daily rainfall over YRB–HRB in the TAI sense is significantly higher than that in the climatological sense. This result suggests that TAI-related synoptic-scale disturbances can significantly increase extreme rainfall over YRB–HRB, which can be well captured by well-performing models.

In observations, El Niño events can increase the TAI-extreme ratio, primarily because they significantly increase the probability of positive TAI occurrences (see z test results in Table  2 ). Most models fail to simulate increased TAI-extreme ratios during El Niño because they cannot capture significantly positive TAI values in the El Niño sense (see Table  2 ). Figure  6 shows the observed daily rainfall PDFs in the climatological sense, TAI sense, and El Niño sense. The results indicate that El Niño events indeed increase extreme rainfall in YRB–HRB, partially attributable to interannual-scale circulation variability (i.e., WNPAC). However, we find that the daily rainfall PDFs in the TAI sense (red curve in Fig.  6 ) are significantly more right-skewed than the PDFs in the El Niño sense (green curve in Fig.  6 ). Additionally, the 95th percentile threshold difference between the El Niño sense (vertical green line in Fig.  6 ) and the climatological sense (vertical blue line in Fig.  6 ) is 0.6 mm/day, which is much lower than the difference between the TAI sense and the climatological sense (1.76 mm/day). This result suggests that on the day-to-day variability scale, TAI-induced circulations have a much greater impact on rainfall than El Niño. In summary, El Niño events have an indirect effect on rainfall in YRB–HRB on the synoptic timescale, mediated by TAI.

YRB–HRB daily precipitation probability density function (PDF) in climatological sense (blue curve), El Niño sense (green curve), and TAI sense (red curve) based on APHRODITE. The 95th percentile values of the daily precipitation associated with the climatological sense (15.94 mm day −1 ), El Niño sense (16.54 mm day −1 ), and TAI sense (17.7 mm day −1 ) are indicated by blue, green, and red vertical lines, respectively

Subsequently, we delve into two key issues: Firstly, based on observations, how does El Niño modulate synoptic-scale features associated with TAI-extremes? Secondly, why do TAI-extremes during El Niño fail to exhibit enhancement compared to climatology in well-performing models?

Figure  7 illustrates the 250 hPa geopotential height anomalies regressed onto TAI in both climatological sense (Fig.  7 a, d) and El Niño sense (Fig.  7 b, e), as well as the difference between the latter and the former (Fig.  7 c, f), based on observations (Fig.  7 a–c) and MME mean of well-performing models (Fig.  7 d–f). In both climatological and El Niño senses, both observations and MME mean exhibit significant wave-like disturbances in the geopotential height. These upper-level disturbances, characterized by a deep upper trough (ridge) over Mongolia–Northern China (SEC–South Korea–Japan), are associated with the tropospheric southward (northward) displacement of cold (warm) advection (see Fig.  3 ). Further examination of the 250 hPa geopotential height anomalies differences between the El Niño and climatological senses reveals enhanced trough-ridge activity during El Niño, with negative (positive) anomalies over Lake Baikal–Mongolia–Northern China (Japan) (Fig.  7 c). Thus, the increased activity of synoptic-scale waves in the upper troposphere during El Niño can lead to more frequent cold and warm temperature advection, conducive to more TAI-extremes. Conversely, MME fails to replicate the observed upper-level waves changes during El Niño (Fig.  7 f), resulting in no significant difference between El Niño-TAI-extreme and TAI-extreme ratios.

Same as Fig.  5 , but for 250 hPa geopotential height anomalies (shading; m). The purple crosses in a , b indicate that geopotential height anomalies pass the 99% significance level. Purple crosses in d – f indicate locations over which more than 80% of models agree on the sign of geopotential height anomalies between the MME mean and each model

Synoptic-scale activities in the lower troposphere between the climatological (Fig.  8 a, d) and El Niño senses (Fig.  8 b, e) are further examined, focusing on 700 hPa temperature. Both observed (Fig.  8 a, b) and simulated (Fig.  8 d, e) outcomes illustrate a north–south oriented temperature dipole pattern, characterized by anomalous cooling (warming) over Mongolia-Northern China (SEC–South Korea–Japan), evident in both observations and MME of well-performing models. Observations reveal a temperature difference between the El Niño and climatological senses, indicating negative (positive) anomalies over Mongolia–Northern China (SEC–South Korea–Japan) during El Niño, suggesting a stronger meridional temperature gradient over EA (Fig.  8 c). This intensified north–south oriented temperature gradient, associated with frontal activities, is primarily attributed to the heightened upper-level trough-ridge pattern in El Niño sense, thereby creating conducive conditions for TAI-extremes. Conversely, the MME mean shows no significant changes in temperature perturbation during El Niño (Fig.  8 f), consistent with the earlier finding that models fail to capture changes in the El Niño-TAI-extreme ratio.

Same as Fig.  7 , but for 700 hPa temperature (shading; ℃)

6 El Niño impacts on synoptic-scale activities represented by TAI

The above results indicate that, for observations, El Niño favors the enhancement of synoptic-scale activities represented by TAI, consequently increasing extreme precipitation over YRB–HRB. Here we investigate how El Niño strengthens these synoptic-scale activities and why models fail to capture these phenomena. Considering that the enhanced synoptic-scale upper-level waves during El Niño may be influenced by interannual-scale circulation anomalies, we focus on studying seasonal mean anomalies during El Niño. Furthermore, models' deficiency in reproducing upper-level wave activities during El Niño may also be affected by bias in the mean circulation. In light of this, we will next discuss the potential relationship between seasonal mean anomalies during El Niño and synoptic-scale activities.

SST anomalies in the equatorial region can drive local convection and diabatic heating, inducing upper-tropospheric circulation anomalies in remote areas through the propagation of Rossby waves to mid-high latitudes (Hoskins and Karoly 1981 ). To understand the extra-tropical Rossby wave dispersion during El Niño, the 250 hPa wave activity flux is analyzed. Figure  9 shows the composite 250 hPa geopotential height anomalies and the associated wave activity flux during El Niño, for observations (Fig.  9 a) and MME mean (Fig.  9 b). Regarding observations, geopotential height anomalies exhibit two stationary wave patterns (SWP) in mid-high latitudes during El Niño. One SWP is characterized by alternating positive and negative anomalies originating from the Atlantic, extending throughout the entire northern Eurasian continent, and finally reaching EA. This elongated zonally oriented SWP, spanning almost 30°W–120°E, traverses the EA region and propagates along the East Asian westerly jet (EAWJ), referred to as EAWJ-SWP. Another SWP is found in the North Pacific–North America (PNA) region, starting from the North Pacific with negative anomalies, propagating northeastward, and ultimately penetrating into the central-western part of North America with positive anomalies (PNA-SWP, hereafter). MME can replicate the PNA-SWP with a stronger and equatorward-displaced pattern, but it does not capture the EAWJ-SWP during El Niño (Fig.  9 b). The investigation further delves into the upper-level zonal wind patterns during El Niño. Observations show a north–south alternation of positive and negative zonal wind anomalies spanning the entire Eurasian continent (Fig.  10 a). The most notable aspect is the enhanced EAWJ during El Niño, with similar findings observed in previous studies (Horel 1981 ; Wang 2002 ; Yang et al. 2002 ). In contrast, MME cannot reproduce the enhanced EAWJ (Fig.  10 b). Additionally, observations show an obvious alternation of positive and negative zonal wind anomalies across the entire PNA region (Fig.  10 a). While this PNA anomaly pattern can be captured by the MME, it appears with a larger magnitude and a northwestward displacement (Fig.  10 b). These findings indicate that models exhibit poor performance in simulating the EAWJ-SWP teleconnections during El Niño.

Same as Fig.  2 , but for 250 hPa wave activity flux (vectors; m 2 s −2 ) and 250 hPa geopotential height anomalies (shading; m). The vectors less than 0.2 m 2  s −2 are omitted. The purple crosses in a indicate that geopotential height anomalies passing the 90% significance level. The purple crosses in b indicate locations over which more than 80% of models agree on the sign of geopotential height anomalies between MME and each model

Same as Fig.  2 , but for 250 hPa zonal wind (shading; m s −1 ). The black crosses in a indicate zonal wind anomalies passing the 90% significance level. The black crosses in b indicate locations over which more than 80% of models agree on the sign of zonal wind anomalies between MME and each model

Possible reasons for the poor performance of models in capturing the EAWJ-SWP teleconnections during El Niño are now considered. Figure  11 displays the climatology of 250 hPa zonal winds and stationary wavenumbers (Ks) in both observations (Fig.  11 a) and MME (Fig.  11 b), along with the model biases (Fig.  11 c). The observed and simulated upper-level zonal winds exhibit strong westerlies within the 20°N–40°N axis, featuring two maximum jet centers located in the Atlantic and EA regions, respectively (Fig.  11 a, b). Although the MME mean can generally capture upper-level background winds, biases in 250 hPa zonal winds still exist, characterized by a globally meridional positive–negative–positive tri-pole pattern (Fig.  11 c), as supported by previous studies (Ma et al. 2015 ; Fu et al. 2020 ). The inadequate simulation of El Niño-related EAWJ-SWP teleconnections might be due to the equatorward-displaced jet bias. To further validate this viewpoint, we calculated the Ks of the background zonal wind at 250 hPa to explore the wave trapping effects of the westerly jet. For observations, we identified continuous Ks = 5 waveguides crossing the Atlantic westerly jet (AWJ) and EAWJ (Fig.  11 a), which is consistent with previous findings (Li et al. 2020 , 2021c ). Under such conditions, El Niño events are more likely to trigger EAWJ-SWP teleconnections. In contrast, for MME, we find discontinuous Ks = 5 waveguides along the AWJ-EAWJ, particularly with clear interruptions at the entrances of the AWJ and EAWJ (Fig.  11 b). This bias hinders zonal Rossby waves propagation, resulting in the absence of EAWJ-SWP teleconnections during El Niño in MME.

Climatology of 250 hPa zonal winds (shading; m s −1 ) based on a NCEP reanalysis data and b MME mean of well-performing models. c Climatological ensemble-mean 250 hPa zonal wind biases (shading; m s −1 ) from the reanalysis climatology. The solid black contour indicates the stationary wavenumber (Ks) of 5. Black crosses in b indicate locations over which more than 80% of models agree on the sign of biases of zonal wind between MME and each model

Diabatic heating serves as the source triggering quasi-stationary planetary waves (Seo and Son 2012 ; Wiel et al. 2015 ). Thus, the diabatic heating bias in models significantly contributes to the observed bias in stationary Rossby waves (Park and Lee 2021 ). Here, we examine the anomalous vertically integrated (from surface to 100 hPa) atmospheric apparent heat source during El Niño based on observations (Fig.  12 a) and models (Fig.  12 b) (as described in detail by Hsu and Li 2011 ). Observations indicate that there are positive heat source anomalies observed in the tropical central-eastern Pacific, while negative anomalies are found in the tropical western Pacific. In contrast, the MME mean shows an amplified and westward-displaced heat source anomalies in the tropical Pacific during El Niño (Fig.  12 b, c). Previous studies indicated that GCMs commonly exhibit a mean-state SST cold tongue bias in the tropical Pacific (Li et al. 2019a , b ; Wang et al. 2019 ; Li et al. 2021b ), and the well-performing models in this study are no exception (highlighted in the red box in Fig.  13 ). Previous study also showed that the excessive SST cold tongue bias in models tends to result in a westward shift of diabatic heating anomalies in the tropical Pacific during El Niño, as also seen in Fig.  12 . Importantly, this mean-state SST cold tongue bias not only affects the tropics but also leads to stronger and more westward-shifted forcing; this can result in westward displaced PNA-SWP teleconnections and bias in the EAWJ-SWP teleconnection (see Figs.  9 and 10 ). Previous studies suggested that the mean-state SST cold tongue bias in the tropics significantly affects the models' ability to simulate the atmospheric response in mid-high latitudes (Bayr et al. 2019 ; Li et al. 2019a , b ). Therefore, due to the presence of mean-state SST cold tongue bias in well-performing models, the EAWJ-SWP teleconnections during El Niño cannot be captured.

Same as Fig.  11 , but for anomalies of vertically integrated atmospheric apparent heat source (shading; W m −2 ) during the subsequent MAM season of the El Niño, along with their ensemble-mean bias (shading; W m −2 ). The black crosses in a indicate heat source anomalies passing the 90% significance level. The black crosses in b , c indicate locations where more than 80% of models agree on the sign of heat source anomalies between MME and each model

SST mean-state bias (shading; K) in the MME of well-performing models. Black crosses indicate locations over which more than 80% of models agree on the sign of SST bias between MME and each of model. The red box (170°E–80°W; 2°S–2°N) denotes the mean-state SST cold tongue bias

Section  5 emphasizes that El Niño events strengthen the upper-level synoptic-scale waves along the EAWJ. Here, focusing on observations (Fig.  14 a) and MME (Fig.  14 b), we examine the relationship between the anomalies in 500 hPa EGR during El Niño and synoptic-scale disturbances. In observations, we observe positive anomalies of EGR along the EAWJ extending to the EA–Pacific region, indicating stronger atmospheric baroclinicity and resulting in more synoptic-scale activities in this broad area. Consequently, a higher TAI-extreme ratio can be observed during El Niño compared to the climatological sense. However, the anomalies in EGR cannot be captured in the MME mean, thus consistent with the absence of linkage between TAI synoptic-scale activities and El Niño. The EGR bias during El Niño in models may arise from two main reasons: the westerly jet background bias and mean-state SST cold tongue bias. Specifically, the westerly jet background bias leads to discontinuous waveguides along the AWJ-EAWJ, preventing the models from reproducing the observed-like EAWJ-SWP in mid-high latitudes (including EGR anomalies along the EAWJ) during El Niño. Additionally, the excessive SST cold tongue bias in the tropical Pacific reduces the model's ability to simulate El Niño-related teleconnections in mid-high latitudes, leading to a failure to capture EAWJ-SWP teleconnections and EGR anomalies along the EAWJ.

Same as Fig.  2 , but for 500 hPa EGR (shading; day −1 ). The black crosses in a indicate EGR anomalies passing the 90% significance level. The black crosses in b indicate locations over which more than 80% of models agree on the sign of EGR anomalies between MME and each model

7 Discussion and conclusions

This study examines the impact of El Niño on extreme precipitation over SEC using both observational data and CMIP6 models. During El Niño in the following spring, more-than-normal extreme precipitation over SEC, including the PRB, YRB, and HRB subregions, can be seen in both observations and models. The significant WNPAC during El Niño plays a crucial role in transporting moisture to the SEC region, thereby increasing extreme precipitation over SEC. Furthermore, our study delves into the influence of synoptic-scale disturbances on extreme precipitation over SEC, as well as how El Niño influences these synoptic-scale activities. Both observations and CMIP6 models highlight the close relationship between the cold-warm temperature advection dipole and extreme precipitation over SEC.

Further investigation reveals that TAI derived from daily temperature advection effectively characterizes synoptic-scale activities associated with SEC extreme precipitation. These synoptic-scale activities, represented by TAI, are characterized by upper-level waves and a north–south temperature gradient over EA, significantly contributing to intense precipitation in the NPRB, YRB, and HRB regions. It is important to note that since TAI-related circulations are typical mid-latitude disturbances, their impact on precipitation in the SPRB is minimal. To assess the influence of El Niño on precipitation represented by TAI, we first compared daily rainfall anomalies regressed onto TAI between the El Niño and climatological senses. Observations show increased rainfall over YRB–HRB during El Niño, suggesting that precipitation in the YRB–HRB region may be more susceptible to the influence of synoptic-scale activities during El Niño. However, the MME mean fails to capture such a change for El Niño events. Next, we explore the relationship between TAI and extreme precipitation in the YRB–HRB region, as well as its differences between the El Niño and climatological senses. Both observations and MME mean reveal a significant positive correlation between TAI and extreme precipitation in the YRB–HRB region, with TAI-extreme ratios of 76% and 65%, respectively. Although models underestimate the TAI-extreme ratio, they generally simulate an observed-like relationship between TAI and extreme precipitation over YRB–HRB. Observations show a 9% higher El Niño-TAI-extreme ratio compared to the Clim-TAI-extreme ratio, while both are nearly equal in the MME mean. Subsequently, we focus on how El Niño affects synoptic-scale disturbances represented by TAI in observations, as well as why models fail to capture such changes during El Niño.

In observations, El Niño amplifies upper-level synoptic-scale waves, marked by a deepened trough over Mongolia–Northern China and an enhanced ridge over South Korea-Japan, owing to increased atmospheric instability along the EAWJ. These enhanced upper-level waves contribute to enlarging the meridional temperature gradient over EA. Consequently, more TAI-extremes are observed during El Niño (refer to Fig.  15 for details). In contrast, the MME mean fails to capture the discrepancy in TAI-extreme ratios between the El Niño and Climatological senses due to its inadequate representation of atmospheric instability along the EAWJ during El Niño. The absence of increased atmospheric baroclinicity in MME is primarily caused by its background westerly jet bias and mean-state SST cold tongue bias. Specifically, models commonly exhibit an upper-level zonal wind bias characterized by a globally meridional positive–negative–positive tri-pole pattern. Such a bias leads to the inability of models to replicate observed-like waveguides along the AWJ-EAWJ, ultimately resulting in the failure to reproduce EAWJ-SWP teleconnections during El Niño. Additionally, models also exhibit a mean-state SST cold tongue bias, resulting in a different atmospheric response in mid-high latitudes during El Niño. These two types of mean-state bias result in fewer changes in EGR anomalies along the EAWJ during El Niño. Therefore, improving the ability to simulate the background flow of upper-level zonal wind and mean-state SST in the tropical Pacific region is identified as a critical factor for obtaining reasonable synoptic-scale activities during El Niño.

Flowchart illustrating the mechanisms by which El Niño modulates synoptic-scale disturbances represented by TAI, leading to increased intense precipitation extremes over YRB–HRB

In our study, we examined the mechanisms contributing to extreme precipitation events using observed data and assessed the impacts of El Niño on extreme precipitation. Additionally, we evaluated the ability of CMIP6 models to simulate these mechanisms. More importantly, we identified an index, TAI, which represents synoptic-scale activities and can effectively quantify the frequency of extreme precipitation in SEC. Its significant correlation with El Niño also provides a new perspective on how large-scale circulations influence extreme precipitation on the synoptic timescale. However, TAI has certain limitations as a quantifying factor for extreme precipitation. This is mainly due to its nonlinear relationship with extreme precipitation. The factors influencing extreme precipitation involve complex nonlinear processes, and the intensity of extreme precipitation cannot be quantified solely by TAI. Additionally, our study does not investigate extreme precipitation under future global warming scenarios. Future research should investigate how precipitation extremes change under the influence of global warming compared to historical simulations, and whether there is an increased, reduced, or unchanged relationship between synoptic-scale disturbances and extreme precipitation under the influence of global warming compared to historical simulations.

For the convenience of the readers' understanding of this paper, we have compiled all abbreviations of academic terms mentioned in Table S4. Additionally, we considered the El Niño diversity and briefly discussed the impact of Eastern Pacific El Niño and Central Pacific El Niño on precipitation extremes over SEC. This discussion can be found in S2 of the supplemental materials.

Data availability

The rain-gauge-based daily precipitation data provided by APHRODITE were downloaded from http://aphrodite.st.hirosaki-u.ac.jp/download/ . The NCEP/NCAR reanalysis products were provided by NOAA/OAR/ESRL PSD, Boulder, CO, USA ( https://psl.noaa.gov/data/reanalysis/reanalysis.shtml ). The Sea Surface Temperature dataset provided by Hadley Centre Global Sea Ice and Sea Surface Temperature are available through https://www.metoffice.gov.uk/hadobs/hadisst/index.html . The CMIP6 outputs used in this study are available from the Earth System Grid Federation ( https://esgf-node.llnl.gov ).

Ai Y, Chen H, Sun J (2022) Model assessments and future projections of spring climate extremes in China based on CMIP6 models. Int J Climatol 42:4601–4620. https://doi.org/10.1002/joc.7492

Article   Google Scholar  

Ai Y, Chen H, Sun J (2023) The underestimation of spring precipitation over South China is caused by the weak simulations of the dynamic motion in CMIP6 models. Int J Climatol 43:2586–2600. https://doi.org/10.1002/joc.7991

An D, Eggeling J, Zhang L et al (2023) Extreme precipitation patterns in the Asia-Pacific region and its correlation with El Niño-Southern Oscillation (ENSO). Sci Rep 13:11068. https://doi.org/10.1038/s41598-023-38317-0

Article   CAS   Google Scholar  

Bayr T, DI Domeisen V, Wengel C (2019) The effect of the equatorial Pacific cold SST bias on simulated ENSO teleconnections to the North Pacific and California. Clim Dyn 53:3771–3789. https://doi.org/10.1007/s00382-019-04746-9

Brubaker KL, Entekhabi D, Eagleson PS (1993) Estimation of continental precipitation recycling. J Clim 6:1077–1089. https://doi.org/10.1175/1520-0442(1993)006%3c1077:EOCPR%3e2.0.CO;2

Cao D, Tam C-Y, Xu K (2024) Impacts of El Niño diversity on East Asian summertime precipitation extremes. Clim Dyn 62:4171–4187. https://doi.org/10.1007/s00382-024-07125-1

Chan JCL, Li Z, Du Y, Luo Y (2020) Statistical characteristics of pre-summer rainfall over south China and associated synoptic conditions. J Meteorol Soc Japan 98:213–233. https://doi.org/10.2151/jmsj.2020-012

Chang EKM, Fu Y (2002) Interdecadal variations in Northern Hemisphere winter storm track intensity. J Clim 15:642–658. https://doi.org/10.1175/1520-0442(2002)015%3c0642:IVINHW%3e2.0.CO;2

Chen CA, Hsu HH, Liang HC (2021) Evaluation and comparison of CMIP6 and CMIP5 model performance in simulating the seasonal extreme precipitation in the Western North Pacific and East Asia. Weather Clim Extrem 31:100303. https://doi.org/10.1016/j.wace.2021.100303

Dong T, Dong W (2021) Evaluation of extreme precipitation over Asia in CMIP6 models. Clim Dyn 57:1751–1769. https://doi.org/10.1007/s00382-021-05773-1

Feng J, Chen W, Tam CY, Zhou W (2011) Different impacts of El Niño and El Niño Modoki on China rainfall in the decaying phases. Int J Climatol 31:2091–2101. https://doi.org/10.1002/joc.2217

Feng J, Chen W, Li Y (2017) Asymmetry of the winter extra-tropical teleconnections in the Northern Hemisphere associated with two types of ENSO. Clim Dyn 48:2135–2151. https://doi.org/10.1007/s00382-016-3196-2

Fredriksen H-B, Berner J, Subramanian AC, Capotondi A (2020) How does El Niño-Southern oscillation change under global warming—a first look at CMIP6. Geophys Res Lett 47:e2020GL090640. https://doi.org/10.1029/2020GL090640

Fu Y, Lin Z, Guo D (2020) Improvement of the simulation of the summer East Asian westerly jet from CMIP5 to CMIP6. Atmos Ocean Sci Lett 13:550–558. https://doi.org/10.1080/16742834.2020.1746175

Gao C, Li G (2023) Decadal enhancement in the effect of El Niño in the decaying stage on the pre-flood season precipitation over Southern China. J Clim 36:8155–8170. https://doi.org/10.1175/JCLI-D-22-0864.1

Gao H, Jiang W, Li W (2014) Changed relationships between the East Asian summer monsoon circulations and the summer rainfall in eastern China. J Meteorol Res 28:1075–1084. https://doi.org/10.1007/s13351-014-4327-5

Gao T, Zhang Q, Luo M (2020) Intensifying effects of El Niño events on winter precipitation extremes in southeastern China. Clim Dyn 54:631–648. https://doi.org/10.1007/s00382-019-05022-6

Gao T, Xu Y, Wang HJ et al (2022) Combined impacts of climate variability modes on seasonal precipitation extremes over China. Water Resour Manag 36:2411–2431. https://doi.org/10.1007/s11269-022-03150-z

Grotjahn R (2003) Baroclinic instability. Encycloped Atmos Sci 179:00076–00172

Google Scholar  

Hayasaki M, Kawamura R (2012) Cyclone activities in heavy rainfall episodes in Japan during spring season. SOLA 8:45–48. https://doi.org/10.2151/sola.2012-012

Horel JD (1981) Planetary-scale atmospheric phenomena associated with the southern oscillation. Mon Weather Rev 110:1495–1496. https://doi.org/10.1175/1520-0493(1982)110%3c1495:COSAPA%3e2.0.CO;2

Hoskins BJ, Ambrizzi T (1993) Rossby wave propagation on a realistic longitudinally varying flow. J Atmos Sci 50:1661–1671. https://doi.org/10.1175/1520-0469(1993)050%3c1661:RWPOAR%3e2.0.CO;2

Hoskins BJ, Karoly DJ (1981) The steady linear response of a spherical atmosphere to thermal and orographic forcing. J Atmos Sci 38:1179–1196. https://doi.org/10.1175/1520-0469(1981)038%3c1179:TSLROA%3e2.0.CO;2

Hsu P-C, Li T (2011) interactions between boreal summer intraseasonal oscillations and synoptic-scale disturbances over the western North Pacific. Part II: apparent heat and moisture sources and eddy momentum transport. J Clim 24:942–961. https://doi.org/10.1175/2010JCLI3834.1

Jia X, Cao DR, Ge JW, Wang M (2018) Interdecadal change of the impact of Eurasian snow on spring precipitation over southern China. J Geophys Res Atmos 123:10092–10108. https://doi.org/10.1029/2018JD028612

Jia X, Zhang C, Wu R, Qian Q (2021) Influence of Tibetan Plateau autumn snow cover on interannual variations in spring precipitation over southern China. Clim Dyn 56:767–782. https://doi.org/10.1007/s00382-020-05497-8

Jiang Z, Zhang DL, Liu H (2020) Roles of synoptic to quasi-monthly disturbances in generating two pre-summer heavy rainfall episodes over south China. Adv Atmos Sci 37:211–228. https://doi.org/10.1007/s00376-019-8156-4

Jing H, Sun J (2023) Diverse impacts of strong and moderate intense El Niño-Southern Oscillation events on spring precipitation over Asia. Int J Climatol 43:6300–6313. https://doi.org/10.1002/joc.8206

Kalnay E, Kanamitsu M, Kistler R et al (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteorol Soc 77:437–471. https://doi.org/10.1175/1520-0477(1996)077%3c0437:TNYRP%3e2.0.CO;2

Kim S, Kug JS (2018) What controls ENSO teleconnection to east Asia? Role of Western North pacific precipitation in ENSO teleconnection to east Asia. J Geophys Res Atmos 123:10406–10422. https://doi.org/10.1029/2018JD028935

Kim IW, Oh J, Woo S, Kripalani RH (2019) Evaluation of precipitation extremes over the Asian domain: observation and modelling studies. Clim Dyn 52:1317–1342. https://doi.org/10.1007/s00382-018-4193-4

Kosaka Y, Nakamura H (2006) Structure and dynamics of the summertime Pacific-Japan teleconnection pattern. Q J R Meteorol Soc 132:2009–2030. https://doi.org/10.1256/qj.05.204

Lau K-M (1992) East Asian summer monsoon rainfall variability and climate teleconnection. J Meteorol Soc Jpn 70:211–240. https://doi.org/10.2151/jmsj1965.70.1B_211

Lee S (2000) Barotropic effects on atmospheric storm tracks. J Atmos Sci 57:1420–1435. https://doi.org/10.1175/1520-0469(2000)057%3c1420:BEOAST%3e2.0.CO;2

Li L, Li W, Barros AP (2013) Atmospheric moisture budget and its regulation of the summer precipitation variability over the Southeastern United States. Clim Dyn 41:613–631. https://doi.org/10.1007/s00382-013-1697-9

Li G, Jian Y, Yang S et al (2019a) Effect of excessive equatorial Pacific cold tongue bias on the El Niño-Northwest Pacific summer monsoon relationship in CMIP5 multi-model ensemble. Clim Dyn 52:6195–6212. https://doi.org/10.1007/s00382-018-4504-9

Li Z, Sun Y, Li T et al (2019b) Future changes in east Asian summer monsoon circulation and precipitation under 1.5 to 5 °C of warming. Earth’s Futur 7:1391–1406. https://doi.org/10.1029/2019EF001276

Li RKK, Tam CY, Lau NC et al (2020) Potential predictability of the Silk Road pattern and the role of SST as inferred from seasonal hindcast experiments of a coupled climate model. J Clim 33:9567–9580. https://doi.org/10.1175/JCLI-D-20-0235.1

Li G, Gao C, Lu B, Chen H (2021a) Inter-annual variability of spring precipitation over the Indo-China Peninsula and its asymmetric relationship with El Niño-Southern Oscillation. Clim Dyn 56:2651–2665. https://doi.org/10.1007/s00382-020-05609-4

Li RKK, Tam CY, Lau NC (2021b) Effects of ENSO diversity and cold tongue bias on seasonal prediction of South China late spring rainfall. Clim Dyn 57:577–591. https://doi.org/10.1007/s00382-021-05732-w

Li RKK, Tam CY, Lau NC et al (2021c) Forcing mechanism of the Silk Road pattern and the sensitivity of Rossby-wave source hotspots to mean-state winds. Q J R Meteorol Soc 147:2533–2546. https://doi.org/10.1002/qj.4039

Li Y, Deng Y, Cheung H-N et al (2022) Amplifying subtropical hydrological transition over China in early summer tied to weakened mid-latitude synoptic disturbances. NPJ Clim Atmos Sci 5:40. https://doi.org/10.1038/s41612-022-00259-1

Liao C, Xu H, Deng J, Zhang L (2018) Interannual relationship between ENSO and Atlantic storm track in spring modulated by the Atlantic multidecadal oscillation. Atmosphere (Basel). https://doi.org/10.3390/atmos9110419

Lindzen RS, Farrell B (1980) A simple approximate result for the maximum growth rate of baroclinic instabilities. J Atmos Sci 37:1648–1654. https://doi.org/10.1175/1520-0469(1980)037%3c1648:ASARFT%3e2.0.CO;2

Liu Y, Wang L, Zhou W, Chen W (2014) Three Eurasian teleconnection patterns: spatial structures, temporal variability, and associated winter climate anomalies. Clim Dyn 42:2817–2839. https://doi.org/10.1007/s00382-014-2163-z

Lui YS, Tam CY, Lau NC (2019) Future changes in Asian summer monsoon precipitation extremes as inferred from 20-km AGCM simulations. Clim Dyn 52:1443–1459. https://doi.org/10.1007/s00382-018-4206-3

Ma J, Xu H, Lin P (2015) Meridional position biases of East Asian subtropical jet stream in CMIP5 models and their relationship with ocean model resolutions. Int J Climatol 35:3942–3958. https://doi.org/10.1002/joc.4256

Palmén E, Newton CW (1969) Atmospheric circulation systems. Academic Press, New York, p 603

Park M, Lee S (2021) Is the stationary wave bias in CMIP5 simulations driven by latent heating biases? Geophys Res Lett 48:e2020GL091678. https://doi.org/10.1029/2020GL091678

Peixto JP, Oort AH (1984) Physics of climate. Rev Mod Phys. https://doi.org/10.1103/RevModPhys.56.365

Qin Y, Lu C, Li L (2017) Multi-scale cyclone activity in the Changjiang River-Huaihe River valleys during spring and its relationship with rainfall anomalies. Adv Atmos Sci 34:246–257. https://doi.org/10.1007/s00376-016-6042-x

Rayner NA, Parker DE, Horton EB et al (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J Geophys Res Atmos. https://doi.org/10.1029/2002jd002670

Sawyer JS, Sutton OG (1997) The vertical circulation at meteorological fronts and its relation to frontogenesis. Proc R Soc Lond Ser A Math Phys Sci 234:346–362. https://doi.org/10.1098/rspa.1956.0039

Seo K-H, Son S-W (2012) The global atmospheric circulation response to tropical diabatic heating associated with the madden-Julian oscillation during northern winter. J Atmos Sci 69:79–96. https://doi.org/10.1175/2011JAS3686.1

Takaya K, Nakamura H (2001) A formulation of a phase-independent wave-activity flux for stationary and migratory quasigeostrophic eddies on a zonally varying basic flow. J Atmos Sci 58:608–627. https://doi.org/10.1175/1520-0469(2001)058%3c0608:AFOAPI%3e2.0.CO;2

Tan Y, Yang S, Zwiers F et al (2022) Moisture budget analysis of extreme precipitation associated with different types of atmospheric rivers over western North America. Clim Dyn 58:793–809. https://doi.org/10.1007/s00382-021-05933-3

Trenberth KE (1997) The Definition of El Niño. Bull Am Meteor Soc 78:2771–2777

Van Oldenborgh GJ, Hendon H, Stockdale T et al (2021) Defining El Niño indices in a warming climate. Environ Res Lett 16:44003. https://doi.org/10.1088/1748-9326/abe9ed

Wang C (2002) Atmospheric circulation cells associated with the El Nino-Southern Oscillation. J Clim 15:399–419. https://doi.org/10.1175/1520-0442(2002)015%3c0399:ACCAWT%3e2.0.CO;2

Wang B, Zhang Q (2002) Pacific-East Asian teleconnection. Part II: How the Philippine Sea anomalous anticyclone is established during El Niño development. J Clim 15:3252–3265. https://doi.org/10.1175/1520-0442(2002)015%3c3252:PEATPI%3e2.0.CO;2

Wang B, Wu R, Fu X (2000) Pacific-East Asian teleconnection: How does ENSO affect East Asian climate? J Clim 13:1517–1536. https://doi.org/10.1175/1520-0442(2000)013%3c1517:PEATHD%3e2.0.CO;2

Wang Z, Duan A, Yang S, Ullah K (2017) Atmospheric moisture budget and its regulation on the variability of summer precipitation over the Tibetan plateau. J Geophys Res. https://doi.org/10.1002/2016JD025515

Wang P, Tam CY, Xu K (2019) El Niño-East Asian monsoon teleconnection and its diversity in CMIP5 models. Clim Dyn 53:6417–6435. https://doi.org/10.1007/s00382-019-04938-3

Wang P, Tam CY, Lau NC, Xu K (2021a) Future impacts of two types of El Niño on East Asian rainfall based on CMIP5 model projections. Clim Dyn 56:899–916. https://doi.org/10.1007/s00382-020-05510-0

Wang S-X, Zuo H-C, Sun F et al (2021b) Dynamics of east Asian spring rainband and spring-autumn contrast: environmental forcings of large-scale circulation. J Clim 34:1–59. https://doi.org/10.1175/JCLI-D-20-0501.1

Wiel K, Matthews A, Joshi M, Stevens D (2015) The influence of diabatic heating in the South Pacific Convergence Zone on Rossby wave propagation and the mean flow. Q J R Meteorol Soc. https://doi.org/10.1002/qj.2692

Wu X, Mao J (2016) Interdecadal modulation of ENSO-related spring rainfall over South China by the Pacific Decadal Oscillation. Clim Dyn 47:3203–3220. https://doi.org/10.1007/s00382-016-3021-y

Wu R, Hu ZZ, Kirtman BP (2003) Evolution of ENSO-related rainfall anomalies in East Asia. J Clim 16:3742–3758. https://doi.org/10.1175/1520-0442(2003)016%3c3742:EOERAI%3e2.0.CO;2

Wu C-H, Lee S-Y, Chiang JCH, Tsai P-C (2023) Role of precession on the transition seasons of the Asian monsoon. NPJ Clim Atmos Sci 6:95. https://doi.org/10.1038/s41612-023-00426-y

Wu S, Luo M, Liu Z et al (2024) Longer- and slower-moving contiguous heatwaves linked to El Niño. Geophys Res Lett 51:e2024GL109067. https://doi.org/10.1029/2024GL109067

Xu J, Zhang Q, Bi B, Chen Y (2022) Spring extreme precipitation days in North China and their reliance on atmospheric circulation patterns during 1979–2019. J Clim 35:2253–2267. https://doi.org/10.1175/JCLI-D-21-0268.1

Xue D, Lu J, Leung LR et al (2023) Robust projection of East Asian summer monsoon rainfall based on dynamical modes of variability. Nat Commun 14:3856. https://doi.org/10.1038/s41467-023-39460-y

Yang S, Lau KM, Kim KM (2002) Variations of the East Asian jet stream and Asian-Pacific-American winter climate anomalies. J Clim 15:306–325. https://doi.org/10.1175/1520-0442(2002)015%3c0306:voteaj%3e2.0.co;2

Yang S, Wu R, Jian M et al (2021) characteristics of the spring–summer atmospheric circulation transition over the south China sea and its surrounding regions and their responses to global warming, pp 7–79. https://doi.org/10.1007/978-981-15-8225-7_2

Yatagai A, Kamiguchi K, Arakawa O et al (2012) Aphrodite constructing a long-term daily gridded precipitation dataset for Asia based on a dense network of rain gauges. Bull Am Meteorol Soc 93:1401–1415. https://doi.org/10.1175/BAMS-D-11-00122.1

Zhang M, Meng Z (2018) Impact of synoptic-scale factors on rainfall forecast in different stages of a persistent heavy rainfall event in south China. J Geophys Res Atmos 123:3574–3593. https://doi.org/10.1002/2017JD028155

Zhang J, Li L, Zhou T, Xin X (2013) Evaluation of spring persistent rainfall over East Asia in CMIP3/CMIP5 AGCM simulations. Adv Atmos Sci 30:1587–1600. https://doi.org/10.1007/s00376-013-2139-7

Zhong W, Wu Y, Yang S et al (2023) Heavy southern China spring rainfall promoted by multi-year El Niño events. Geophys Res Lett 50:e2022GL102346. https://doi.org/10.1029/2022GL102346

Zhou X, Liu F, Wang B et al (2019) Different responses of East Asian summer rainfall to El Niño decays. Clim Dyn 53:1497–1515. https://doi.org/10.1007/s00382-019-04684-6

Zhu Z, Lu R, Fu S, Chen H (2022) Alternation of the atmospheric teleconnections associated with the northeast china spring rainfall during a recent 60-year period. Adv Atmos Sci. https://doi.org/10.1007/s00376-022-2024-3

Download references

Acknowledgements

This work was jointly sponsored by the National Key Research and Development Program of China (2019YFC1510400), National Natural Science Foundation of China (42076020, 42105040), Guangdong Basic and Applied Basic Research Foundation (2023B1515020009, 2024B1515040024), Youth Innovation Promotion Association CAS (2020340), Science and Technology Planning Project of Guangzhou (2024A04J6275) and special fund of South China Sea Institute of Oceanology of the Chinese Academy of Sciences (SCSIO2023QY01).

Author information

Authors and affiliations.

Department of Earth and Environmental Sciences, The Chinese University of Hong Kong, Hong Kong, China

Dingrui Cao & Chi-Yung Tam

Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China

State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China

You can also search for this author in PubMed   Google Scholar

Contributions

Dingrui Cao: Conceptualization, Data curation, Formal analysis, Methodology, Writing—original draft. Chi-Yung Tam: Conceptualization, Supervision, Funding acquisition, Writing—review and editing. Kang Xu: Conceptualization, Writing—review and editing, Funding acquisition.

Corresponding author

Correspondence to Chi-Yung Tam .

Ethics declarations

Conflict of interest.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Publisher's note.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Below is the link to the electronic supplementary material.

Supplementary file 1 (DOCX 13611 KB)

Rights and permissions.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cao, D., Tam, CY. & Xu, K. The influence of El Niño on springtime synoptic-scale precipitation extremes in Southeastern China: insights from CMIP6 model simulations. Clim Dyn (2024). https://doi.org/10.1007/s00382-024-07445-2

Download citation

Received : 17 June 2024

Accepted : 09 September 2024

Published : 24 September 2024

DOI : https://doi.org/10.1007/s00382-024-07445-2

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

• Springtime extreme precipitation
• Southeastern China
• Upper-level synoptic-scale waves
• Temperature advection index
• Find a journal
• Publish with us
• Track your research