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This study investigates the connection between significant sea surface temperature (SST) anomalies in the North Pacific during boreal spring (February–April, FMA) and the subsequent South China Sea (SCS) summer monsoon (SCSSM) onset. The SST anomalies, similar to the Pacific meridional mode (PMM), referred to as the PMM+ mode, are defined to examine the new influencing factor on the SCSSM onset. Our findings reveal that the (February–March–April, FMA) PMM+ has a noteworthy positive correlation with the subsequent May SCSSM onset date, with this correlation being minimally affected by the El Niño–Southern Oscillation (ENSO) during preceding winter. A robust positive PMM+ in boreal spring can be persist until May via atmosphere–ocean interaction. The cooling area over Western North Pacific would reduce precipitation heating, thereby generating Rossby waves that reinforce the formation of the anomalous anticyclone over the SCS. As a result, easterly winds and suppressed convection prevail over the SCS, making the SCSSM break out later than normal. Furthermore, the amplification of anticyclonic vorticity anomalies also strengthens the western North Pacific subtropical high (WNPSH) stronger and shifts its position further westward compared to normal years, thereby blocking active convection to the west of the SCS. Given the weakened relationship between El Niño–Southern Oscillation (ENSO) and the SCSSM onset in recent years, the PMM+ could be considered as a promising preceding signal for the SCSSM onset, thus holding significant implications for the SCSSM prediction efforts. [ABSTRACT FROM AUTHOR]

Frequent occurrences of extreme heats in recent years pose a threat to the local society, economy, and ecosystem in Southern China. Understanding the process and predictability of these heat events is crucial for scientific research and policy-making. The long-term variation characteristics and the corresponding driving factors of high-temperature days (HTDs) and surface air temperature (SAT) in midsummer in Southern China were analyzed by observed data of meteorological stations and atmospheric reanalysis data. The results reveal an abrupt rise in HTDs around the early 2000s during the period of 1979–2021, rather than a sustained increase. Prior to and after this mutation, no clear trend is observed. The changes in SAT align closely with the variations in HTDs. The abrupt increase in solar radiation, resulting from a decrease in total cloud cover, is identified as the direct cause of the SAT change. In the decade following the abrupt change point, significant anomalous descent motion and low-level divergent winds over Southern China are observed, creating favorable climatic conditions for the rise in SAT. The primary driving factor behind these circulation changes is identified as the Pacific interdecadal oscillation, which shifted from a positive to a negative phase during the same period. This shift led to the strengthening of the Walker circulation and the formation of an anomalous anticyclone over the northwest Pacific. It is worth noting that current mainstream climate dynamical models failed to capture the abrupt rise in SAT, instead exhibiting a sustained increasing trend that compromised the accuracy of the forecast. This discrepancy may be attributed to the models' slow response to rapid changes in sea surface temperature. [ABSTRACT FROM AUTHOR]

By observing well‐known sea surface temperature (SST) indices and outputs from Climate Forecast System version 2 (CFSv2) hindcasts and predictions, in this study, we developed a hybrid statistical downscaling prediction model (HSDPM) based on a timescale decomposition approach, which effectively improved the forecasting ability of summer (June–August) precipitation over Hainan Island (HNSP) in China; this precipitation presented multiple obvious timescale variabilities. We found that the interannual variability of the HNSP is closely related to the observed North Atlantic tripole SST anomalies in the preceding winter and the summer sea level pressure over the South China Sea by CFSv2 predicted in March. On the other hand, the interdecadal variability in the HNSP is linked to the prewinter Pacific Interdecadal Oscillation (PDO) according to the observations, the CFSv2 predictions of the summer surface air temperature over the tropical central‐east Pacific. On this basis, both the interannual and interdecadal components of the HNSP are effectively predicted using the corresponding predictors via multiple regression; thus, the HSDPM is ultimately established by combining the above two components. Compared with the original CFSv2 model, the HSDPM model achieves a considerable improvement in performance in predicting the HNSP. Specifically, the temporal correlation coefficient, ratio of root‐mean‐square error and anomaly sign consistency rate between the observed and HSDPM‐predicted HNSPs are 0.70, 17.4% and 80.5%, respectively, which are significantly greater than the above three forecasting index values of 0.23, 38.3% and 48.8%, respectively, obtained from the original CFSv2 predictions. The application of the HSDPM may be beneficial for drought and flood prevention and mitigation in Hainan Island. [ABSTRACT FROM AUTHOR]

The South China Sea summer monsoon (SCSSM) onset and withdrawal have critical impacts on the climate of East Asia. However, using different reanalysis data may lead to the uncertainty of the SCSSM. This study uses reanalysis datasets including JRA‐55, ERA5, NCEP‐NCAR NCEP‐1 and NCEP‐DOE NCEP‐2 to calculate onset and withdrawal dates and index of SCSSM from 1991 to 2020, analyses the uncertainty and figures out the possible reasons. Results reveal that the four reanalysis datasets have obvious uncertainty in calculating the withdrawal date of SCSSM, with the deviation being up to 3.4 pentads. Further analysis shows that large differences in thermal conditions and lead to the uncertainties. From the perspective of precipitation, Greater uncertainty exists in the relationship between monsoon retreat and September–October precipitation, NCEP1 and NCEP2 datasets show weak correlation in southern China and Indonesia. Moreover, the uncertainty can be also found in the correlations of SCSSM with global sea surface temperature (SST) anomalies. JRA‐55 and ERA5 show a strong correlation of with SST in several areas, and exhibit a distinct Pacific decadal oscillation (PDO) mode with monsoon onset, while NCEP‐1 and NCEP‐2 have a weaker correlation with SST anomalies than JRA‐55 or ERA5. Comparing multiple factors comprehensively, this paper concludes that JRA‐55 may be more representative in the monsoon study, followed by ERA data. In short, depending on the specific research questions, researchers can choose appropriate data sources to study the SCSSM based on the different aspects and the uncertainty also deserve our special attention when selecting the reanalysis datasets. [ABSTRACT FROM AUTHOR]

Heat waves, droughts, and compound drought and heat waves (CDHWs) have received extensive attention because of their disastrous impacts on agriculture, ecosystems, human health, and society. Here, we computed the heat wave magnitude index (HWMI), drought magnitude index (DMI), and compound drought and heat wave magnitude index (CDHMI) for Yangtze River Valley (YRV) from July to August during 1961–2022. We compared the large-scale atmospheric circulation characteristics of different extreme events based on these indexes. The results show that the positive center with sink motion in East Asia provides a favorable circulation background for heat wave events. Drought events are mainly affected by the zonal wave train dominated by a significant negative anomaly in Siberia and a high-pressure anomaly upstream, and a anticyclonic water vapor with strong divergence over the Yangtze River basin. During CDHW events, both anomalous systems that affect heat waves and droughts appear and strengthen simultaneously. Specifically, in the middle and upper troposphere, the positive height anomaly center in YRV expands abnormally, and the "+–+" wave train over the northern 50° N region of East Asia becomes more obvious. Therefore, the positive anomaly and water vapor anomaly brought by the two circulation patterns at different latitudes are superimposed over the YRV, leading to severe CDHWs. At the same time, the warm positive eddy center and cold negative eddy center in high latitudes exhibit more stable positive pressure features, which are conducive to the persistent development and strengthening of CDHWs. In addition, the anomalous warm sea surface temperature in western Pacific moderating the favorable circulation patterns may also promote the occurrence of CDHWs in the YRV during the same period. [ABSTRACT FROM AUTHOR]

By using the 43 Historical experiments from phase 6 of the Coupled Model Intercomparison Project (CMIP6) and 45 Historical experiments from phase 5 of CMIP (CMIP5) for the period of 1950–2005, we comprehensively assess the improvements in simulating the spatial pattern, warming trend, climatology and interannual variation of sea surface temperature (SST) in China offshore sea (COS) from CMIP5 to CMIP6 models. Both CMIP6 multi-model ensemble mean (CMIP6 MME) and CMIP5 multi-model ensemble mean (CMIP5 MME) well simulated the spatial pattern of climatological-mean COS SST, but they tend to underestimate the warming trends of COS SST at both seasonal and interannual timescales, which is due to the low estimations of SST warming rate before the late 1970s, particularly for the CMIP6 models. Nevertheless, both the simulated trend biases and inter-model uncertainties are reduced from CMIP5 to CMIP6 models during the period 1979–2005. Compared to the simulated annual-mean and seasonal-mean COS SST in the CMIP5 models, the inter-model uncertainties and cold biases of SST simulated by the CMIP6 models have been significantly reduced, particularly for the autumn-mean and summer-mean SST. Similarly, the CMIP6 models perform better than the CMIP5 models in simulating the interannual variation of COS SST, as evidenced by a much lower interannual variability skill score over the South China Sea and Huang&Bo China Sea. Furthermore, more than 60% of CMIP6 models perform better than their counterpart CMIP5 models in simulating the spatial patterns and interannual variations of annual-mean and seasonal-mean COS SST based on the rank of individual models performance and comprehensive ranking measure ordering. Additionally, the insignificant improvement of the evident warm bias in the East China Sea during winter and spring and cold bias in the Huang&Bo China Sea during spring and summer from CMIP5 to CMIP6 models is primarily associated with the defect of the ocean dynamical processes. [ABSTRACT FROM AUTHOR]

The predictability and variability of extratropical climate are largely associated with tropical forcing through various teleconnections. The East Asia–Pacific/Pacific-Japan (EAP/PJ) teleconnection is one of the most important factors affecting the summer climate in East Asia. In this work, we confirm the weakening relationship between the El Niño-Southern Oscillation (ENSO) and the following summer PJ teleconnection after the late 1990s and diagnose the possible causes. The results show that compared with that of in 1981–1998, ENSO is less conducive to the formation of anomalous anticyclones in the following summer in the Northwest Pacific (NWP) and the northward propagating Rossby wave train from latitudes of NWP in 2000–2017, resulting in a weaker summer PJ teleconnection. Meanwhile, variation of ENSO feature since 2000 with a suppressed variability leads to a weakened response in the tropical Indian Ocean in the spring and summer. The reduced sea surface temperature response in the tropical Indian Ocean suppresses the excitation of eastward-propagating Kelvin waves and declines the capacitor effect of the Indian Ocean, which is unfavorable for generating anomalies in the NWP and motivating strong PJ teleconnection in meridional direction. Thus, the weakening relationship of ENSO-PJ after late 1990s is the result of the weakened ENSO's impact on the formation of anticyclones in the following summer in NWP and the declined Indian Ocean capacitor effect on motivating meridionals wave train over East Asia and NWP region. [ABSTRACT FROM AUTHOR]

The effects of El Niño-Southern Oscillation (ENSO) on winter precipitation in South China are considerably asymmetric. A positive correlation is significant between the sea surface temperature anomalies (SSTA) in the equatorial middle-eastern Pacific and the precipitation in South China during El Niño winters, whereas no significant relationship instead of a negative correlation between them during La Niña winters. The possible causes of abnormally positive precipitation in South China during La Niña winters remain a puzzle. The analysis indicates that positive precipitation anomalies in South China during La Niña winters are closely related to the strengthening of southerly winds over the South China Sea and convective activities over South China. Moreover, during La Niña winters, the low-level southerly wind anomalies over the South China Sea are modulated by an anomalous positive local zonal sea surface temperature gradient (SSTG) between the South China Sea and the tropical western Pacific, which strengthens in late autumn and maintains through the following winter. This positive local zonal SSTG is independent of La Niña and leads to the weakening of Walker circulation. The strengthened downward motion over the tropical western Pacific further promotes the weakening of local Hadley circulation. Weakened local Hadley circulation, with strengthened southerlies over the South China Sea in the lower troposphere, is conducive to the enhancement of water vapor transport from the South China Sea to South China. Besides, the weakened local Hadley circulation also shows strengthened upward motion over South China, which provides more advantageous dynamic conditions for precipitation. Therefore, the positive local zonal SSTG simultaneously promotes the two most important conditions affecting precipitation, resulting in positive precipitation anomalies over South China during La Niña winters. These results advance the understanding of prediction of winter precipitation in south China. [ABSTRACT FROM AUTHOR]

In 2021, the Yangtze–Huaihe River Basin (YHRB) of China underwent normal precipitation during the classical Meiyu period in June–July but suffered extreme precipitation and severe floods in August. The present study revealed that the extreme heavy precipitation anomalies over the YHRB region were closely related to the combined effect of the strong western North Pacific anomalous anticyclone (WNPAC) and East Asian middle–high latitude circulation anomalies in August 2021. Moreover, the background of sea surface temperature (SST) anomalies was a strong eastern-Pacific La Niña event that rapidly decayed in spring and a second La Niña emerged in late summer, accompanied by a weak tropical Indian Ocean warming and a strong tropical Atlantic warming in summer. The rapidly decaying La Niña event and the weak tropical Indian Ocean warming alone seem to be insufficient to induce the strong WNPAC in August 2021. Observational evidence and numerical experiments suggest that the rapid tropical Atlantic warming from late spring to summer observably contributed to the enhancement and westward shift of the WNPAC, and the cold SST anomalies in the eastern tropical Pacific associated with the second La Niña event also provided favorable conditions for a strong WNPAC in August 2021. Overall, rapid tropical Atlantic warming and the development of the second La Niña contributed to the strong WNPAC in August 2021, while the maintenance mechanism of the East Asian middle–high latitude circulation anomalies that controlled cold air activity remains unclear. [ABSTRACT FROM AUTHOR]

The maximum signal-to-noise ratio empirical orthogonal function (MSN-EOF) is used to evaluate the midsummer 2 m temperature over Eastern China using subseasonal forecast data in the ECMWF model. The predictable sources of the most predictable components in the ECMWF model are analyzed, and the improvement of reconstructed predictions with leading predictable components is also investigated. ECMWF has the highest forecast ability among all S2S models but decays significantly after 10 d. The leading predictable mode mainly presents a dipole mode over Eastern China. Both the El Niño-Southern Oscillation and tropical Indian Ocean sea surface temperature anomalies are the main predictable sources of MSN-EOF1. A positive MSN-EOF1 is accompanied by El Niño decay, which can cause the strong and westward West Pacific Subtropical High, accompanied by anomalous southwesterlies over the north of Eastern China. The second predictable mode is the warmer characteristic of the Yangtze-Yellow River Basin, and the sea ice anomalies over the Barents Sea in the previous winter are the main predictable sources. This is accompanied by the wave train propagating from northwestern Russia to northeast Asia. The third predictable mode is mainly the temperature trend item extracted from the ECMWF model. The reconstructed predictions with the leading four MSN-EOF components show higher ability than the model raw predictions, therefore, this method can use the predictable components to filter the model noise and reduce the model error. [ABSTRACT FROM AUTHOR]

The Pacific‐Japan (PJ) pattern is the dominant teleconnection over East Asia, closely related to the summer precipitation on various time scales. However, studies on the connection between the interdecadal variations of the PJ pattern and sea surface temperature (SST) forcing are still limited. This study indicates that the relationship between the PJ pattern and ENSO presents a pronounced interdecadal change around 1997/1998. The PJ pattern shows a baroclinic structure over the northwest Pacific and a barotropic structure near Japan during 1979–1997, while its baroclinic structure in the tropics weakens remarkably during 1998–2021, with a southward shift of its midlatitude barotropic structure. As a result, the connection between the PJ pattern and summer precipitation over East Asia exhibits an interdecadal transition in the late 1990s. In the slow La Niña decaying summer of 1979–1997, the cold SST anomalies in the tropical Indian Ocean (TIO) excite an eastward‐propagating Kelvin wave that enhances convection over the northwest Pacific, resulting in the formation of the PJ pattern. In contrast, the cold SST anomalies in the Maritime Continent rather than the TIO yield a zonally confined Kelvin wave in the rapid La Niña decaying summer of 1998–2021. The elongated Kelvin wave penetrating the central Pacific weakens convective anomalies over the northwest Pacific, thereby weakening the baroclinic structure of the PJ pattern in the tropics. Meanwhile, the warm SST anomalies in the Kuroshio Extension (KE) induce a northward shift of the East Asian subtropical westerly jet, with the anomalous anticyclonic circulation over the KE significantly affecting summer precipitation along the Meiyu belt. Therefore, the midlatitude barotropic structure of the PJ pattern shifts southward after the late 1990s. [ABSTRACT FROM AUTHOR]

Herein, we investigated the characteristics and mechanisms of interannual variability of extreme summer precipitation in northwest China (NWC). The four high-resolution precipitation predicting products under assessment indicated that both the accumulation of summer daily precipitation ≥95th percentile, and the summer maxima of daily precipitation generally decreased in a southeast—northwest direction, while relatively high values were observed in the Tienshan and Qilian Mountain areas. In turn, the Tropical Rainfall Measuring Mission (TRMM) satellite dataset underestimated extreme precipitation in mountainous areas, while Asian precipitation highly—resolved observational data integration towards evaluation (APHRODITE) and Climate Prediction Center (CPC) captured the characteristics of extreme precipitation in NWC. AMIP-type simulations of the interannual variability of extreme summer precipitation in NWC were quite unsuccessful. However, all of them can capture the increasing trends. Therefore, we further found that the interannual increase in extreme precipitation in NWC is strongly correlated with the weakened South Asian high, strengthened Western Pacific Subtropical high, the enhanced westerly jet, and the mid- to high-latitude Rossby wave trains, whose formation and sustenance can be traced back to sea surface temperature-anomalies in the western Pacific in May, June, and July. An increased sea surface temperature promotes convection and induces diabatic heating, which stimulates anticyclonic anomalies that disturb the enhanced westerly jet, resulting in a barotropic Rossby wave train via the Gill-type response. Additionally, it guides more water vapor convergence to NWC and enhances upward motion via anticyclonic anomalies over western Europe and Eastern Asia, and cyclonic anomalies over Central Asia. [ABSTRACT FROM AUTHOR]

In early summer 2020, eastern China was hit by record-breaking Meiyu rainfall. The anomalous western Pacific subtropical high (WPSH) played a crucial role in this event. This paper exposes the abnormal features of the WPSH and its related vertical circulations and reveals its dynamical causes in this period, from the perspective of the three-pattern decomposition of global atmospheric circulation (3P-DGAC). Analyzing the anomalous spatial patterns of the three stream functions R, H, and W of the horizontal, meridional, and zonal circulations defined by the 3P-DGAC, we discovered that the WPSH described by R at 850 hPa was intensified and westward from the horizontal circulation. For the vertical circulations, the local meridional circulation along East Asia expressed by H manifested an abnormal downdraft at 20° N, which was beneficial to strengthening the WPSH. The zonal circulation in the tropical Pacific represented by W was anomalously far to the west, which was related to the westward extension of the WPSH. Then, to uncover the causes of the anomalous WPSH from the dynamics, we used the vorticity equation based on the 3P-DGAC and found that the negative relative vorticity advection anomaly over the western Pacific played a key role in this event. Due to the positive sea surface temperature (SST) anomaly and enhanced convection over the Maritime Continent (MC), local vertical circulations at low latitudes were significantly activated. The intense local meridional circulation along East Asia carried the relative vorticity from the MC to the western Pacific and strengthened the WPSH. The ascending branch of the zonal circulation in the tropical Pacific moved westward, which may favor the westward extension of the WPSH. This study represents a promising step in revealing the three-dimensional (3D) structure and internal dynamics of anomalous WPSH. [ABSTRACT FROM AUTHOR]

Using hindcast and forecast data from advanced prediction systems of NCEP CFSv2 and JMA/MRI CPSv2 for the winter 1982/1983–2017/2018, this study investigates the predictability of the climatology and dominant modes of winter-mean surface air temperature (SAT) over East Asia. Although the simulated climatological mean SAT has a large bias over most of the mainland China, both models show high forecasting skills for the principal components (PC1 and PC2) of the two major modes (northern and southern temperature modes) of the winter-mean SAT over East Asia 1 month in advance. In comparison, the MRI-CPSv2 performs better than the CFSv2 in simulating the spatial distribution of the northern temperature mode and the associated circulation anomalies aloft, but the CFSv2 has better performance than the MRI-CPSv2 in simulating the spatial distribution of southern temperature mode and its linkage to the Arctic Oscillation and Eurasian pattern. Furthermore, both models well simulate the impacts of the dipole sea surface temperature (SST) anomalies over the mid-latitude North Pacific and El Niño–Southern Oscillation on the northern and southern temperature modes, respectively. Accordingly, the forecasting skill and signal-to-noise ratio of the PC1 (PC2) are significantly improved in the years with strong SST anomalies over the mid-latitude North Pacific (tropical central-eastern Pacific), particularly for the CFSv2 (MRI-CPSv2) predictions. These results are beneficial for understanding the interannual predictability of the East Asian winter climate. [ABSTRACT FROM AUTHOR]

This paper investigates the causes for the interdecadal change in the relationships between early and late summer precipitation over South China (SC). It is found that the correlations of the precipitation over SC between June and August shift from weak positive in 1979–1995 to significantly negative in 1996–2019. Further analysis demonstrates that the distinct evolution of sea surface temperature (SST) pattern between the two periods accounts for the interdecadal variations of their relationships. Although the warming of the tropical western Indian Ocean (WIO) in June favors increasing precipitation over the SC via enhancing the Northwest Pacific Subtropical High (NWPSH) during the whole period, the associated SST anomalies in August are rather different between the two periods. Specifically, the WIO warming in June corresponds to slightly positive anomalies over the tropical central-eastern Pacific in August during the 1979–1995, which has weak impact on the NWPSH and results in a weak precipitation correlation between June and August. However, the WIO warming in June corresponds to La Niña's rapid development in August during the 1996–2019, which favors the enhancement of the NWPSH via increasing the regional Hadley circulation. Due to the climatologically northward movement of NWPSH from June to August, the enhanced NWPSH in August acts to decrease the precipitation over SC, causing a significantly negative correlation between precipitation in June and August. Overall, the distinct evolution of tropical SST pattern is the key factor inducing the change of the relationships between June and August precipitation in the two periods. [ABSTRACT FROM AUTHOR]

In this study, the East Asian summer (June–July–August) monsoon (EASM) atmospheric moisture transport variability under global warming are examined using ERA‐Interim reanalysis data from 1979 to 2019. The total EASM atmospheric moisture transport is decomposed into the thermodynamic (δTH) and dynamic (δMCD) components, which are related to specific humidity and wind velocity, respectively. Based on empirical orthogonal function (EOF) analysis, both the second and the fourth modes of δTH are linked to δMCD, indicating that δMCD can impact the moisture distribution and consequently influence δTH indirectly. Both the first (δTH_EOF1) and the third (δTH_EOF3) modes of δTH show considerable interdecadal changes. It is noted that their principal components exhibit significant increasing trends in recent decades. The response of EASM moisture transport to global warming is probably reflected in these two modes. δTH_EOF1 is associated with negative phases of the Interdecadal Pacific Oscillation (IPO)/Pacific Decadal Oscillation (PDO). This causes the western North Pacific subtropical high (WNPSH) to extend westward and the strengthening of Pacific trade winds. As a result, positive precipitable water anomalies dominate East Asia and δTH_EOF1 is characterized by anomalous southwesterly moisture transport along the East China Sea to southern Japan. δTH_EOF3 corresponds to anomalous moisture transport over the Indochina Peninsula and Japan. The precipitable water associated with δTH_EOF3 in general represents a meridional dipole. Anomalous southward wind induced by the eastward extension of the WNPSH is the main reason for positive (negative) precipitable water anomalies in southern (northern) East Asian. The anomalous circulation associated with the anomalous east–west sea surface temperature gradient over the Indian Ocean affects atmospheric moisture in southern East Asian and can dramatically impact δTH_EOF3. [ABSTRACT FROM AUTHOR]

Northeast China (NEC) is located between the subtropical monsoon and temperate-frigid monsoon regions and exhibits two successive rainy seasons with different natures: the northeast cold vortex rainy season in early summer (May–June) and the monsoon rainy season in late summer (July–August). Summer rainfall over NEC (NECR) has a fundamental influence on society, yet its successful seasonal prediction remains a long-term scientific challenge to current dynamical models. The poor NECR prediction skill is partly attributed to the large NECR variability at both the interannual and interdecadal time scales. Here, we focus on the oceanic drivers of the late summer NECR variability and associated physical processes at interannual time scale. Then, we establish an empirical prediction model to predict the interannual variability of summer NECR at 1-month lead time (in June). The analysis of observations spanning 40 years (1963–2002) reveals three physically and synergistically influencing predictors of the late summer NECR interannual variability. Above-normal NECR is preceded in the previous spring by (a) warm sea surface temperature (SST) anomalies in the tropical northern Indian Ocean, (b) a positive thermal contrast tendency in the tropical West–East Pacific SST, and (c) a positive tendency of the North Atlantic tripolar SST. These precursors enhance the anomalous low-level anticyclone over the western North Pacific and southerly anomalies over NEC in late summer, which are beneficial to enhancing NECR. An empirical prediction model built on these three predictors achieves a forecast temporal correlation coefficient (TCC) skill of 0.72 for 1961–2019, and a 17-year (2003–2019) independent forecast shows a significant TCC skill of 0.70. The skill is substantially higher than that of five state-of-the-art dynamical models and their ensemble mean for 1979–2019 (TCC = 0.24). These results suggest that the proposed empirical model is a meaningful approach for the prediction of NECR, although the dynamical prediction of NECR has considerable room for improvement. [ABSTRACT FROM AUTHOR]

Tropical Pacific (TP) air–sea coupling is generally accompanied by significant zonal sea surface temperature anomalies (SSTAs) gradient. Here, the wintertime zonal SSTA gradient structures were highlighted in the zonal mean departure SSTA (ZMD-SSTA) field, and separated into two orthogonal dominant components by empirical orthogonal function (EOF) analysis: the west–east dipole (EOF1, 70.7%) and the zonal tripole (EOF2, 23.0%) structure. EOF result comparisons, singular value decomposition (SVD), correlation and composite analyses shows that both the two gradient structures are highly coupled with Walker circulation (WC) but in obviously different spatiotemporal features, and together constitute the vast majority of the coupling variability. Further, the dipole structure can be largely reflected by the indices for eastern-type El Niño-Southern Oscillation (ENSO), but the central-type ENSO indices appears as a superposition of both dipole and tripole structures signals. In rare events of "uncoupled El Niño warming", the two gradient structures can further describe the weaker zonal SSTA gradient under the significant local SSTA in eastern Pacific. These implies that the dipole and tripole structures here may be beneficial to independently reflect the two distinct sea-air coupling structures and supplement the gradient information during ENSO. In addition, the dipole zonal SSTA gradient structure and air-sea feedback associated with it decay rapidly and disappear before the following summer, while the tripole one shows a longer persistence lasting until autumn. The lead–lag relationship with Niño3.4 index indicated that the wintertime tripole SSTA gradient structures precedes the development of ENSO by 1-year. [ABSTRACT FROM AUTHOR]

Southwest China (SWC) is located in the transition zone affected by the East Asia summer monsoons, India monsoon, and the Tibetan Plateau thermal activity. SWC is also an important hub for water vapor transport in the Asia–Pacific (AP) region. Here we study the dynamical and spatiotemporal characteristics of extreme rainfall events in AP by a synchronization network approach, providing insights for understanding of the relevant synchronization mechanisms of extreme rainfall between the SWC and AP. It is found that the probability of significant synchronization rainfall events between SWC and AP as a function of distance changes from a power-law decay behavior to a teleconnection one at around 2000 km. Specifically, the SWC—the middle and lower reaches of the Yangtze River—Japan band (SYJ) is an important teleconnection pattern of extreme rainfall in AP region. This SYJ teleconnection pattern is associated with the water vapor flux convergence along the main water vapor transport route from the low latitude ocean. Moreover, we find that the inter-annual variation of the SYJ teleconnections index can reflect the evolution of synchronization rainfall features from SWC to Japan, which could be useful for operational climate monitoring and prediction. It is also found that the SYJ index is strongly correlated with the sea surface temperature anomalies (SSTA) over the North Indian Ocean and the Western Pacific. The warm Indian Ocean and Western Pacific SST can motivate the transfer of water vapor from SWC to Japan, yielding the synchronization of extreme rainfall along the SYJ band. [ABSTRACT FROM AUTHOR]

In this study, we investigate the interdecadal variation characteristics of the dominant mode of summer precipitation over East Asia‐Northwest Pacific (EA‐NWP) before and after late 1990s, reveal the physical mechanism, and address its possible connection with the regional ocean warming background. Study results show that the empirical orthogonal function mode 1 (EOF1) of summer precipitation anomalies over EA‐NWP during the global ocean warming acceleration period (1979–1998) present a more significant dipole pattern between Yangtze River Basin (YRB) and tropical NWP compared with that during the global ocean warming slowdown period (1999–2012). And then we find that the anomalous dipoles of low‐level winds, geopotential height, convection, and associated wave activity fluxes over NWP significantly shift westward (eastward) and enhance (weaken) in 1979–1998 (1999–2012), which are regarded as the direct cause of the adjustment of dipole pattern between YRB and tropical NWP. Further analysis reveals that the negative sea surface temperature (SST) anomalies in the tropical NWP are prominent (not prominent), resulting in the stronger (weaker) Pacific–Japan Teleconnection over Japan and Tropics in NWP during the period 1979–1998 (1999–2012), and ultimately lead to the change of summer precipitation EOF1 in EA‐NWP. By regressing vertical velocity, outgoing longwave radiation, relative vorticity, wave activity fluxes, and precipitation onto the NWP SST in the two periods, the impacts of the SST in the NWP on the interdecadal variation of summer precipitation EOF1 in EA‐NWP are verified. Finally, the mechanism diagram of interdecadal variation of summer precipitation is given, which can be useful for short‐term precipitation prediction of East Asia. [ABSTRACT FROM AUTHOR]

This study identifies a strengthened relationship between the subtropical Indian Ocean dipole (SIOD) during January–February–March (JFM) and the following autumn Indian Ocean dipole (IOD) after the late 2000s. Following the positive SIOD, the northwesterly wind anomalies help to maintain positive sea surface temperature (SST) anomalies in the southwestern tropical Indian Ocean by wind‐evaporation‐SST (WES) feedback during June–July–August (JJA). The anomalous northwesterly winds and the sustained positive SST anomalies promote the development of the zonal wavenumber‐3 pattern (ZW3P) and induce low‐level convergence in the mid‐latitude central southern Indian Ocean, leading to the anticyclone circulation over the northern Indian Ocean by the local Hadley circulation during JJA. The accompanying central equatorial easterly wind anomalies appear in JJA, which is the key to trigger a positive IOD event through Bjerknes feedback. This mechanism for the enhanced SIOD‐IOD relationship is independent from the El Niño‐Southern Oscillation (ENSO). Plain Language Summary: Both the Indian Ocean dipole (IOD) and the subtropical Indian Ocean dipole (SIOD) are important sea surface temperature (SST) dipole modes in the Indian Ocean. The El Niño‐Southern Oscillation (ENSO) is a well‐known key factor for the evolution of IOD events. However, the relationship between the IOD and the ENSO weakened after the late 2000s. Here, we find the enhanced relationship between the SIOD and the IOD after the late 2000s. The sustained positive SST anomalies related to the SIOD and the zonal wavenumber‐3 pattern in the mid‐latitude southern hemisphere induce the central equatorial zonal winds through the local Hadley circulation, leading to the onset of an IOD event in summer. The mechanism for the enhanced SIOD‐IOD relationship is independent from the ENSO and tends to trigger the IOD earlier than the common IOD, which may help to understand IOD diversity. Key Points: The enhanced relationship between the Indian Ocean dipole (IOD) and the subtropical Indian Ocean dipole (SIOD) appears after the late 2000sThe mechanism for the enhanced relationship between the SIOD and the IOD is independent from ENSO and supports an early IOD onsetThe IOD events are associated with the preexisting SIOD events via the zonal wavenumber‐3 pattern and the local Hadley circulation [ABSTRACT FROM AUTHOR]

By using the hindcast and forecast data from the National Centers for Environmental Prediction Climate Forecast System version 2 (NCEP CFSv2) for the 1982–2018 period, we investigate the forecasting skills of the mid‐summer (July and August) surface air temperature (SAT) at interannual timescales in this study. Although CFSv2 predictions show a warm bias for the climatological mean SAT over the Yangtze River valley (25°–32°N, 105°–122°E), they show a consistent and great performance in predicting the interannual variability of the mid‐summer SAT over this region until 4 months in advance, where the linear correlation coefficient between the predicted and observed time series reaches +0.65, +0.51 and + 0.68 for 4, 2 and 0 months in advance, respectively. The CFSv2 predictions well simulate the linkage between the SAT anomalies over the Yangtze River valley and the anomalous atmospheric circulation aloft, including the circumglobal teleconnection and zonal extension of the Western Pacific Subtropical High. However, CFSv2 has trouble in simulating the associated vertical velocity, cloud cover and solar radiation anomalies, except for 0 months in advance. The persistent forecasting skills result from the accurate response of the circumglobal teleconnection and Western Pacific Subtropical High to the El Niño/Southern Oscillation and sea surface temperature (SST) anomalies over the mid‐latitude North Atlantic. Correspondingly, the forecasting skill, signal and signal‐to‐noise ratio are effectively improved in the years with strong mid‐summer SST anomalies over the tropical central‐eastern Pacific or mid‐latitude North Atlantic. These results are useful for understanding the predictability of the mid‐summer SAT over the Yangtze River valley. [ABSTRACT FROM AUTHOR]

This article uses wave activity flux and sea surface temperature (SST) to explore the mechanism of EAP-EU combined impact on summer rainfall in North Asia (NA). EAP and EU teleconnections can be divided into four categories of configuration according to their anomaly phase features. The category I (II) configurations cause rainfall in the Urals and the Okhotsk Sea and the region from Northeast China to Japan being less (more), the Lake Baikal to the Okhotsk Sea being more (less), which leads to the summer rainfall in NA mainly presenting the "− + −" ("+ − +") a tripole wavelike structure. Category I (II) configurations also show the West-East reverse anomalies of summer rainfall in northern NA and the North-South opposite anomalies in eastern NA. The EAP and EU teleconnections have an obvious correlation with the ENSO-like pattern of SST anomalies over the tropical Pacific. When warm ENSO is in the development phase, it is conducive to stimulate Rossby waves propagating eastward from the North Atlantic Ocean via the PNA teleconnection, forming the EU teleconnection across the Eurasia continent. Meanwhile, the warm summer SSTA anomalies over tropical east Pacific and IMC are conducive to the local thermal convective over Indo-Pacific warm pool and motivate the EAP teleconnection, propagating northward to mid-high latitude region. EAP and the EU teleconnections overlapped with each other, form the tripole atmospheric structure in NA, and produce relevant rainfall anomaly patterns. For the category IV of EAP-EU configuration, the warm SST anomalies in the equatorial region gradually weaken from previous winter to summer. Weak tropical east Pacific SST anomalies are conducive to excite the EU teleconnection with different wave train features against the category II, presenting a strong positive anomaly center over the Ural mountain and Baikal lake. This positive center connected with the EAP caused positive anomalies over FER resulting in the dipole pattern of atmospheric and rainfall anomalies in the summer season. The condition is opposite for the category III (I) configuration against that of category IV (II). It is also found that the influence on EAP-EU configuration caused by ENSO-like pattern of SST anomalies over the tropical Pacific has an obvious asymmetric feature that category II (I) configuration relevant SST forcing is much significant than that of category IV(III) configuration. [ABSTRACT FROM AUTHOR]

Sea surface temperature anomalies (SSTAs), including their spatial patterns and temporal evolution, are an important source of potential predictability for climate anomalies, especially on seasonal to interannual timescales. In this study, the spatial patterns and temporal evolution of tropical SSTAs are identified by applying an extended empirical orthogonal function (EEOF) analysis of observed data from autumn to the following spring. The positive phase of first EEOF mode (EEOF1) displays an El Niño–Southern Oscillation (ENSO) phase‐locking evolution pattern in the tropical Pacific, with accompanying warming in the Indian and Atlantic oceans. EEOF2 is characterized by the development of ENSO in the eastern tropical Pacific and a phase transition in the Indian Ocean and the tropical North Atlantic. The most noticeable feature of EEOF3 is the development of the central Pacific ENSO. The first three EEOF modes account for 44.7% of the total variance of tropical SSTAs over the course of the three seasons. EEOF1 is closely related to the tropical atmospheric circulation, especially over the western Pacific region, reflecting the strengthening effect of the three tropical oceans on the anomalous anticyclone over the tropical Northwest Pacific during the decaying phases of El Niño. EEOF2 significantly impacts the circulation anomalies over the Indian Ocean and western Pacific. A linear regression model is established using the time series of first four EEOF modes to forecast the June to August 500 hPa geopotential height anomalies. The forecasts show higher skill than a similar linear regression model using seasonal mean regional SST anomaly indices. The results reveal that EEOF modes could be used as a good indicator in the monitoring of tropical SSTA evolution patterns. [ABSTRACT FROM AUTHOR]

The aim of this study is to explore the long‐term trends in the distribution of global monsoon precipitation over recent decades using the Global Precipitation Climatology Project (GPCP) data set. In addition, the potential4 mechanisms are examined by applying the atmospheric moisture budget decomposition method to the outputs from the ERA‐Interim medium‐range weather forecasting reanalysis produced by the European Centre for Medium‐Range Weather Forecasts (ECMWF). Changes in global monsoon precipitation are primarily thermodynamically caused by changes in specific humidity and dynamically caused by changes in circulation, as well as by changes in moisture transport that are driven by transient eddies and local evaporation. The results show that the increasing trends in global summer monsoon precipitation from 1979 to 2016 were dominated by contributions from the southern Asian, South African, and North American monsoon regions and were driven by the response of atmospheric circulation to the enhanced east–west thermal contrast in the tropical Pacific. We find that changes in the sea surface temperature (SST) patterns promote increased low‐level vertical velocities in monsoon regions, leading to moisture convergence through divergent circulation anomalies when combined with the climatological humidity field. Hence, the processes result in increasing trends in monsoon precipitation. In addition, evaporation makes increasing contributions to monsoon precipitation throughout the world, except in the South American monsoon region. Moreover, subtropical regions in the East Pacific (the Atlantic) may be major sources of water vapour that have supported increases in precipitation over the southern Asian and North American monsoon regions (the South African monsoon region) in recent decades. Linear trends in (a) precipitation, (b) the moisture convergence term, (c) evaporation, and (d) residual term (precipitation minus the divergence of vertically integrated moisture transport term and evaporation) in local summer (May–September in the Northern Hemisphere and November–March in the Southern Hemisphere) from 1979 to 2016 (unit: mm day−1 year−1). The black curves depict the monsoon domains. Stippled regions indicate statistical significance at the 95% level or higher, as determined using the Mann–Kendall trend test. [ABSTRACT FROM AUTHOR]

This study investigates the changing relationship between the December North Atlantic Oscillation (NAO) and the following February East Asian trough (EAT) throughout the past 60 years. We found that the relationship between the December NAO and the following February EAT is significantly enhanced after the late 1980s compared with the period before the late 1980s. The changing relationship mainly results from the enhanced relationship between the December NAO and the following February North Atlantic mid-latitudes' sea surface temperature (SST) anomalies (NAMA) during the same period. During the period after the late 1980s, the persistent positive (negative) NAO pattern from December to the following January contributes to a positive (negative) NAMA, which reaches its maximum magnitude in the following February and excites an anomalous wave train along the North Atlantic and northern Eurasia, and significantly impacts the EAT. During the period before the late 1980s, the positive (negative) NAO pattern during December cannot persist into the following January, and the related positive (negative) NAMA is insignificant during the following February, causing the response of the simultaneous EAT to be insignificant as well. Moreover, there exists a significant impact of the December NAO on the December-January NAMA after the late 1980s, while the December-January NAMA is relatively less affected by the December NAO before the late 1980s. As a result, the simultaneous response of the atmospheric circulation anomalies to the December-January NAMA are evident before the late 1980s, and the positive (negative) NAMA can excite an anomalous wave train along the North Atlantic and northern Eurasia and significantly deepen (shallow) the downstream EAT. By contrast, after involving a feature of atmosphere forcing of SST, the simultaneous feedback of the December-January NAMA on EAT is significantly decreased after the 1980s. [ABSTRACT FROM AUTHOR]

Using the monthly reanalysis data sets of National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) for 1961–2015, the inter‐decadal change in inter‐annual water vapour transport over the tropical Indian Ocean–western Pacific during summer and the related mechanisms were analysed in this article. The results show that two major modes of anomalous water vapour transport over the tropical Indian Ocean–western Pacific (60°–140°E, 10°S–30°N) experienced a significant inter‐decadal change in the mid‐1980s. The first mode (EOF1) shows that the anticyclonic water vapour transport over the northwestern Pacific moves significantly southwards after the mid‐1980s. Before the mid‐1980s, the anomalous water vapour originates from the subtropical western Pacific and moves through the South China Sea to eastern China. However, the anomalous water vapour mainly originates from the tropical western Pacific and moves through the South China Sea to eastern China after the mid‐1980s. The second mode (EOF2) reflects the enhanced effect of the anomalous water vapour transport over the tropical Indian Ocean on East Asia after the mid‐1980s. Before the mid‐1980s, the distribution of the water vapour anomalies is uneven over the tropical Indian Ocean and the magnitude of water vapour is relatively small, so it has a weak effect on rainfall over East Asia. After the mid‐1980s, anomalous anticyclonic water vapour transport originates from the tropical Indian Ocean and moves along the Arabia Sea, Indian Peninsula and Indo‐China Peninsula and then forms an anomalous cyclonic water vapour transport over south China. Furthermore, the possible causes of the inter‐decadal transition in anomalous water vapour transport are investigated for the two major modes. The significant inter‐decadal transition in anomalous water vapour transport is associated with the enhanced effect of the sea surface temperature (SST). Before the mid‐1980s, the relationships between the two major modes and the SST of the tropical oceans are relatively weak. After the mid‐1980s, the EOF1 becomes significantly regulated by the El Niño‐Southern Oscillation (ENSO) in the previous winter, and the positive (negative) phase of the principal component of the first mode (PC1) corresponds to significantly positive (negative) SST anomalies over the tropical northern Indian Ocean and Maritime Continent during the same period. For EOF2, the anomalous water vapour transport over the tropical Indian Ocean is related to the enhanced inter‐annual variability of tropical Indian Ocean dipole (TIOD) after the mid‐1980s. [ABSTRACT FROM AUTHOR]

Considering the possible lag of the impact of the winter Arctic oscillation (AO) on the subsequent summer climate anomalies over East Asia and that the relationship between them may differ during different periods, the non-stationary relationship between these systems and the corresponding mechanism of connection are investigated in this study. A regime shift of the winter AO index was detected around 1988, with mean AO indices of −0.69 and 0.10 for 1958-1987 and 1988-2014, respectively, and their differences passed the 99% confidence level. After the regime shift and especially since the early 1990s, negative (positive) winter AO indices corresponds with positive (negative) height anomalies over central East Asia (CEA) during the following summer. Meanwhile, the westerly jet stream tends to be northward (southward) and the East Asian summer monsoon (EASM) is strong (weak), which contributes to the warm (cold) anomalies over central China and the significantly enhanced (reduced) rainfall over northeast China. After the early 1990s, the enhanced connection of the winter AO and the following summer height anomalies over CEA is largely due to the enhanced connection of the winter AO and the following Indian summer monsoon (ISM) rainfall during the same period. The negative (positive) winter AO favors increasing (decreasing) rainfall over the ISM region, which triggers a positive (negative) circumglobal teleconnection (CGT), and results in significantly positive (negative) height anomalies over CEA. One way the winter AO could influence the following ISM rainfall is that the negative (positive) winter AO memories will be maintained by the positive (negative) sea surface temperature (SST) anomalies over the tropical Atlantic of the following summer, which are responsible for the La Niña (El Niño) developing phase and increases (decreases) the ISM rainfall. [ABSTRACT FROM AUTHOR]

ABSTRACT The western Pacific subtropical high ( WPSH) and sea surface temperatures have experienced marked interdecadal changes. However, whether the relationships between the WPSH and sea surface temperature forcings ( SSTFs) have also experienced an interdecadal transition remains unclear. This study analyses the interdecadal shift in the relationship between the WPSH and SSTFs. The results clearly reveal the occurrence of two interdecadal transitions in the relationship between the leading empirical orthogonal function modes, which represent the intensity of the WPSH and the SSTFs: one in approximately 1976-1977 and the other in 1993-1994. The positive first principal component is closely related to the equatorial eastern and central Pacific ( EECP) warming and the western North Pacific ( WNP) cooling in spring and summer of the three periods. The discharging process of the 'Indian Ocean Capacitor Effect' in summer was suppressed by the downdraft during the periods 1978-1992 and 1995-2013, which caused the tropical Indian Ocean ( TIO) warming to have little influence on the WNP anomalous anticyclone ( WNPAC) in summer. The positive second principal component corresponds to significantly positive sea surface temperature anomalies in the TIO, the maritime continent, the WNP, the North Pacific cooling in spring and summer, and the EECP cooling in the summer, while it is significantly related to only the positive-phase North Atlantic tripole ( NAT) in the spring in the years 1954-1975. The enhancement of the WNPAC by the NAT was partly offset by the tropical North Atlantic warming with a positive tropospheric temperature anomaly. Additionally, an anticyclone over the North Pacific Ocean accelerated the phase shift of El Niño/Southern Oscillation from El Niño to La Niña in the spring in the years 1995-2013. [ABSTRACT FROM AUTHOR]

The intraseasonal variations of summer precipitation anomalies in the Meiyu area of East Asia are analyzed by applying a combined empirical orthogonal function (CEOF) of the latest meteorological reanalysis data ERA5 of European Center for Medium-Range Weather Forecasts for the period from 1991 to 2020, and the circulation structures and sources of variability of CEOF are also investigated. The first mode of the intraseasonal variations shows an in-phase pattern over the Meiyu area in June, July, and August, accounting for 22.2% of the total variance in the intraseasonal variations of summer precipitation anomalies. The positive (negative) CEOF1 is accompanied by the negative (positive) East Asia/Pacific pattern, including strong westerly wind anomalies in the upper troposphere and southwest monsoon in the lower troposphere, and the Western Pacific Subtropical High extending westward and its ridge line slightly south. The positive CEOF1 is preceded by decay of El Niño episodes, including the abnormal warm sea surface temperature anomalies (SSTAs) in the equatorial Central-Eastern Pacific in spring and warm SSTAs in the equatorial Indian Ocean in summer. The second mode shows an opposite precipitation anomaly in June and July, and the distribution in August is not significant. The corresponding geopotential height circulation of positive CEOF2 shows the large negative anomaly in the region north of 40° N and a positive anomaly over Japan in June, whereas the pattern reverses in July. At the same time, there is a radical reversion from abnormal eastly to westly wind in the upper troposphere. The structure of CEOF2 is somewhat induced by local SSTAs over the Northern Indian Ocean and South China Sea. [ABSTRACT FROM AUTHOR]

We introduce bilayer networks in this paper to study the coupled air-sea systems. Results show that the framework of bilayer networks is powerful for studying the statistical topology structure and dynamics in the fields of ocean and atmosphere. Based on bilayer networks, the inner and cross interactions of the sea surface temperature (SST) field and the height field are displayed, and the main three-dimensional air-sea interaction pattern is identified. The formation of the main pattern can be explained by the 'gearing between the Indian and Pacific Ocean (GIP)' model; therefore, the pattern existence can be confirmed reliably. Furthermore, lead-lag analysis reveals the trigger processes of the 'GIP'. That is, the anomalies of the tropical mid-eastern Pacific Ocean SST (TMEPO-SST) appear first; then, through the Walker circulation, the 850-hPa geopotential height over the Pacific Islands responds to the anomalies of the TMEPO-SST 2 months later; finally, the tropical Indian Ocean SST (TIO-SST) responds to the anomalies of the height 1 month later through the Asian monsoon circulation. Therefore, the impacts of the TMEPO-SST to the TIO-SST show 3 months later through the air-sea interactions between the components of the main three-dimensional air-sea interaction mode. The new framework uncovers already-known as well as other novel features of the air-sea systems and general circulation. The application of complex network theory and methodology to understand the complex interactions between the oceans and the atmosphere is promising. [ABSTRACT FROM AUTHOR]

Accurate short-term climate predictions, specifically the prediction of dominant rain belts during flood seasons, represent a significant challenge, particularly in the absence of notable external forcing signal anomalies in the previous winter. To address this challenge, we propose a novel climate index based on an Auto-Encoder (AE) Neural Network that exhibits superior performance in indicating several significant precipitation events in the Yangtze and Huaihe River Basins under varying El Niño conditions. Notably, the novel climate index rectifies the discrepancy between the 2019/2020 Niño index and the 2020 summer precipitation. In order to understand the information source of AE, the causality between AE and other indices was further analyzed by Granger Causality. The results show that AE index mainly contains the information of subtropical high index and ocean index, which is consistent with previous studies. • AE obtained by Auto-encoder can make up for the "failure" of Nino index in abnormally heavy precipitation events. • In terms of magnitude and state, AE has better description of precipitation than Nino3.4. • The main indices of AE information are subtropical high-pressure index and sea surface temperature index. [ABSTRACT FROM AUTHOR]

Atmospheric rivers (ARs), the long and narrow conveyors of intense moisture transport, are a unique mover of moisture from the low latitudes to the mid to high latitudes and have a considerable impact on hydrometeorological events (i.e., extreme precipitation). Using the top-hat by reconstruction (THR) algorithm and ERA5 reanalysis data, this study analyzes the climatological characteristics of ARs over East Asia (EA) in summer (June to August) during 1979–2020. According to the four leading modes of EOF analysis, ARs events occur mainly in the Yangtze River valley, the Huaihe River valley, and the coastal region of South China. The sea surface temperature anomalies (SSTAs) related to the first EOF mode (EOF1) show the warming of the central and eastern Pacific and Indian Oceans. The northward movement of the westerly jet stream maintains the western North Pacific subtropical high (WNPSH) and guides water vapor transport to China. EOF2 corresponds to the positive phase of EAP (East Asia-Pacific) pattern. SSTAs related to EOF2 show an El Niño recession-like pattern, which modulates precipitation over southern China through anticyclones over the western North Pacific. SSTAs related to EOF3 show a La Niña-like pattern, which regulates the precipitation in the Yangtze-Huaihe valley through upper-level convective heating on the north side of the WNPSH. For EOF4, the circulation system affecting ARs is dispersed, resulting in smaller scale ARs. ARs of EOF4 are associated with cyclones, mainly showing the characteristics of coastal landing ARs. These results can provide a new forecasting source for EA summer precipitation. • Atmospheric rivers-related precipitation accounts for 32–40% of the total in East Aisa from 1979 to 2020 in summer. • WNPSH plays a leading role in the changes of East Aisan atmospheric rivers. • The underlying mechanisms behind different types of ARs in East Asia is discussed. [ABSTRACT FROM AUTHOR]