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The Tarim Basin is a large inland arid basin in the arid region of northwest China and has been experiencing significant "warming and wetting" since 1987. As a result, the purpose of this paper is to determine whether the climate transition phenomenon occurred in the Tarim Basin as well as the role of atmospheric circulation in this process. We use meteorological data and atmospheric circulation indexes to study the seasonal trends of climate change in this region from 1987 to 2020 to understand how they are affected by atmospheric circulation. The findings show that, from 1987 to 2020, the Tarim Basin experienced significant warming and wetting; with the exception of the winter scale, all other seasonal scales exhibited a clear warming and wetting trend. From the perspective of spatial distribution, most of the areas showed a significant warming trend, and the warming amplitude around the basin is greater than that in the central area of the basin. However, there are significant regional differences in precipitation change rates. Meanwhile, wavelet analysis shows that there is a significant oscillation period of 17–20 years between climate change and the atmospheric circulation index during 1987–2020. The correlation analysis shows that the Pacific decadal oscillation (PDO) and El Niño-Southern Oscillation (ENSO) are the main influencing factors of climate change in the Tarim Basin at different seasonal scales, while the teleconnection of the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) is low and the PDO dominates the summer and autumn temperature changes in the Tarim Basin. The research results of this paper show that, despite the warming and wetting trends since 1987 in the Tarim Basin, the climate type did not change. From 1987 to 2020, the main teleconnection factors of climate change in the Tarim Basin were PDO and ENSO. [ABSTRACT FROM AUTHOR]

A model‐circulation increment‐based dynamic statistical technique (MIDST) is proposed in this paper to improve the prediction of summer rainfall over southern China (SC) where quite low prediction skills have been found in the Beijing Climate Center Climate System Model version 1.1 with a moderate resolution (BCC_CSM1.1m). The results show that BCC_CSM1.1m can hardly represent the variability of the summer rainfall anomaly and its year‐to‐year increment over SC, and the skillful predictions are mostly confined over the middle reaches of the Yangtze River. Using the dynamic model output and statistical method, the MIDST is established to capture the coupled modes between the year‐to‐year increments of the summer rainfall anomaly and the associated simultaneous three‐dimensional coupled air‐sea circulation predictors. The cross‐validation indicates that the prediction skills of the MIDST are evidently improved for both the summer rainfall increment prediction and summer rainfall anomaly prediction compared with the direct BCC_CSM1.1m prediction. The skillful prediction can persist for long forecast leads over most regions except southwestern China. As the major predictability source of seasonal prediction, the intense response to changes in the circulation related to the El Niño‐Southern Oscillation (ENSO) is well captured, and thus, the performance improvement of the MIDST is primarily due to its more realistic representation of the incremental circulation related to the ENSO. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is well known that El Niño–Southern Oscillation (ENSO) can influence the East Asian winter climate by modifying the atmospheric circulation over the western North Pacific (WNP). While the impact on precipitation in southeastern China has been extensively studied, the ENSO signal in surface air temperature (SAT) remains overlooked. In this paper, we identify robust ENSO footprints in the winter daily minimum SAT in southeastern China, with El Niño winters generally accompanied by warmer-than-normal minimum SAT anomalies. In contrast, the responses of maximum SAT are weak and negligible, suggesting a diurnal cycle–dependent ENSO influence. Further analysis indicates that this diurnal cycle dependence stems primarily from the disparate surface radiative heating between day and night induced by ENSO-related local total cloud cover (TCC) change. The warmer minimum SAT occurring in the early morning of El Niño winters is mainly caused by the enhanced surface downward longwave radiative heating as a result of the TCC increase. However, in the afternoon of El Niño winters, although the anomalous horizontal advection of warm air plays a role, there is surface radiative cooling as the weakening of solar radiation due to TCC reflection overwhelms the increase in downward longwave radiation, which leads to a weakened sensible heat flux and thus has a cooling effect on the SAT. Ultimately, these two processes effectively cancel each other out and together produce insignificant maximum SAT responses. Our conclusions carry important implications for the seasonal to interannual winter climate prediction in southeastern China. Significance Statement The purpose of this study is to better understand how ENSO influences winter surface air temperature in southeastern China. Despite insignificant responses of winter daily maximum temperature to ENSO, we find here a robust ENSO influence on the daily minimum temperature, with warm anomalies tending to occur during El Niño events. Further evidence suggests that this diurnal cycle–dependent ENSO influence is mainly caused by ENSO-induced change in local cloudiness, which has a different radiative heating effect between day and night. Our findings are of great importance for improving regional climate prediction, which will benefit social and economic activities. [ABSTRACT FROM AUTHOR]

The amount of winter precipitation over southeast China (SCWP) is significantly affected by the El Niño–Southern Oscillation (ENSO), with generally an enhanced SCWP response to El Niño events. In this paper, we find that this relationship shows remarkable nonstationarities on the multidecadal timescale. Running ENSO–SCWP correlation maintains statistically significant before the mid‐1960s and after the mid‐1990s but not during the interim period, which exhibits an approximate synchronized temporal evolution with the Atlantic Multidecadal Oscillation (AMO). A statistical method for interpreting nonstationary relationships is then applied to quantitatively verify and measure this possible AMO modulation. It is demonstrated that the nonstationary ENSO–SCWP correlation can be expressed to a large extent by the influence of the AMO–ENSO nonlinear effect (AMO*Niño3.4) on the SCWP. This influence intensifies the ENSO–SCWP relationship during the positive AMO phase but weakens it during the negative AMO phase. Therefore, the nonstationarity in the ENSO–SCWP relationship comes predominantly from an AMO modulation via this key nonlinear effect. We further suggest that a positive AMO favours a westward shift of ENSO sea surface temperature (SST) anomaly pattern in the tropical Pacific. Correspondingly, the anomalous western North Pacific (WNP) anticyclone also migrates westward, which gives rise to pronounced moisture transports and vertical motions over the adjacent southeast China, thereby resulting in a significant ENSO–SCWP relationship. In contrast, during the negative AMO phase, the eastward‐shifted ENSO SST and WNP anticyclonic anomalies produce significant atmospheric anomalies primarily to the east of the Chinese mainland, thus having less effect on the SCWP. [ABSTRACT FROM AUTHOR]

The transport of atmospheric moisture presents a crucial role in the global hydrological cycle. In this paper, we performed an empirical orthogonal function (EOF) investigation of integrated moisture transport (IVT) which was observed to be connected with the renowned regional climate phenomenon named El Nino–Southern Oscillation (ENSO) in China. Results explained that in the Eastern and Southern China Sea, and Southeastern China, IVT variances were high, and could change significantly yearly. However, in Northern China, variances were quite low, meaning that monthly IVT was more predictable. The spatial distribution of IVT anomalies was different with the seasons. Summer, in particular, exhibited significantly higher IVT values across the equatorial western Pacific, and there was also a transfer of moisture from the tropical Indian Ocean to the Northwestern and Southeastern China. The primary six modes of the EOFs together explained about 52.3%, which accounted for greater than half of the variation in the IVT anomalies. The main mode was related to ENSO and it explained approximately 16.4% variance in the Southern China Sea and central equatorial Pacific, while the second mode illustrated about 10.8% variance and was strongest in the East China Sea and entire Southeastern China. The cross-wavelet coherence indicated that the IVT and ENSO time-series were coherent, having a duration of about 2–8 years. This thus implied that increased IVT was linked with enhanced ENSO activities. This study could contribute to a better perception of how atmospheric circulation patterns could modify the general flow of the atmosphere to affect normal weather conditions in China. [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper analyses the different relationships between the two types of South Asian highs (SAH)—the southern mode of the SAH (SSAH) and the traditional SAH in its entirety (ESAH)—with respect to the variations in summer rainfall over East Asia. The ESAH is closely related to summer rainfall over northeastern China, whereas the SSAH is closely linked to summer rainfall over the Yangtze River valley, northern China, and Japan. Above‐normal rainfall tends to occur over northeastern China in strong ESAH years, whereas strong SSAH years tend to yield above‐normal rainfall over the Yangtze River valley and Japan together with below‐normal rainfall over northern China. The westerly jet and the western Pacific subtropical high (WPSH) shifts northward associated with a strengthened ESAH. The related anomalous southwesterly winds to the northwestern side of the WPSH transports abundant water vapour to northeastern China and leads to above‐normal rainfall there. In contrast, the westerly jet shifts southward and WPSH shifts southwestward to the South China Sea associated with a strengthened and southeastward‐shifted SSAH. Accordingly, a cyclonic anomaly appears over Northeast Asia and mid‐latitude western northern Pacific and an anticyclonic anomaly occurs over subtropical western North Pacific. The associated southwesterly wind anomalies over the Yangtze River valley and Japan contributes to above‐normal rainfall over these regions via transporting sufficient amount of water vapour. In addition, the anomalous northerly winds to the western flank of the cyclonic anomaly results in below‐normal rainfall over northern China via carrying drier air southward. Furthermore, the preceding winter ENSO events may play a more important role in the SSAH variation via modulating India Ocean SST. [ABSTRACT FROM AUTHOR]

This paper presents a review on the impact of El Niño on the interannual variability of atmospheric circulations over East Asia and rainfall in China through the anomalous anticyclone over western North Pacific (WNPAC). It explains the formation mechanisms of the WNPAC and physical processes by which the WNPAC affects the rainfall in China. During the mature phase of El Niño, the convective cooling anomalies over western tropical Pacific caused by the weakened convections trigger up an atmospheric Rossby wave response, resulting in the generation of the WNPAC. The WNPAC can persist from the winter when the El Niño is in its peak to subsequent summer, which is maintained by multiple factors including the sustained presence of convective cooling anomalies and the local air-sea interaction over western tropical Pacific, and the persistence of sea surface temperature anomalies (SSTA) in tropical Indian and tropical North Atlantic. The WNPAC can influence the atmospheric circulations over East Asia and rainfall in China not only simultaneously, but also in the subsequent summer after an El Niño year, leading to more rainfall over southern China. The current paper also points out that significant anomalies of atmospheric circulations over East Asia and rainfall over southern China occur in El Niño winter but not in La Niña winter, suggesting that El Niño and La Niña have an asymmetric effect. Other issues, including the impact of El Niño diversity and its impact as well as the relations of the factors affecting the persistence of the WNPAC with summer rainfall anomalies in China, are also discussed. At the end of this paper some issues calling for further investigation are discussed. [ABSTRACT FROM AUTHOR]

The periodicities of the climate change have long been explored by researchers not only because they reflect the inherent characteristics of the climate systems, but also because they are the foundations of climate-change predictability. This paper reports the periodicities of the hydroclimate variations reconstructed from a lacustrine sequence at Tiancun section (TC section) in the Luoyang Basin within the Central Plains of China and the sequence covers the first half of the Holocene. Our reconstruction shows that the hydroclimate variations at the TC section during the period from ∼10,135 and ∼ 5890 cal. yr BP were well corresponding with the effective soil moisture variations recorded by the stalagmite δ13C sequence at the Magou Cave. This corresponding relationship suggests that when the effective soil moisture increases (i.e., more negative δ13C values), the ratio of evaporation over precipitation in the paleolake at the TC section decreased, resulting in lower CaCO 3 content. It also suggests that when the effective soil moisture increases, more inflowing water entered the paleolake, resulting in coarser sediments. Our reconstruction also shows that the hydroclimate variations or lake level variations in the Luoyang Basin were characterized by millennial-scale quasi-periodicities that were most likely paced by the changes in ITCZ (Inter-tropical Convergent Zone) position and also by alterations in ENSO-like phase. And, both (ITCZ and ENSO) were most likely regulated by the solar activity. Our further analysis shows that the hydroclimate in the Luoyang Basin also experienced centennial-scale variations. Specifically, the grain size data express the following cycles: 692-year, 538-year, 217-year, 170-year and 123-year, all at the 99% confidence level. And, the CaCO 3 content data express the following cycles: 202-year, 184-year, 169-year and 85-year, all at the 99% confidence level. These cycles are approximately coincident with the widely-reported solar-activity cycles. • This paper reports the periodicities of the hydroclimate variations reconstructed from a lacustrine sequence in the Central Plains of China and the sequence covers the first half of the Holocene. • The hydroclimate variations were primarily paced by changes in ITCZ position and also by alterations in ENSO-like phase. And, both (ITCZ and ENSO) were most likely regulated by solar activity. • The centennial-scale hydroclimate variations were approximately coincident with the widely-reported solar-activity cycles. [ABSTRACT FROM AUTHOR]

• Long-term evolution trend of wind and waves in China's offshore was investigated. • A novel approach was proposed to evaluate wind-wave joint exploitation potential. • Joint utilization guarantee rate of wind and waves in China's offshore was 67 %–87 %. • AO, AMO and Niño 3.4 affected WS and H s from high to low latitudes, respectively. • Impact of ENSO on WS and H s in SCS could reach 3.92 m/s and 1.15 m, respectively. Assessing wind and waves resources and analyzing their evolution are crucial for the exploitation of wind and wave energy. This paper utilized ERA5 reanalysis data to investigate the distribution characteristics, long-term evolution, and influencing factors of wind speed (WS) and significant wave height (H s) in China's offshore regions. It showed that over the past 60 years, the Bohai Sea experienced a significant downward trend in WS (−0.632 cm/s/yr) and H s (−0.135 cm/yr). The Yellow Sea exhibited a downward trend in WS, but no change trend was observed in H s (p > 0.05). The H s in the East China Sea (ECS) and South China Sea (SCS) showed upward trends, increasing by 0.191 cm/yr and 0.262 cm/yr, respectively. The concept of energy utilization guarantee rate (EUGR) was introduced to evaluate the complementarity and synergy between wind and wave resources. The ECS and SCS were found to possess ample wind resources, with an EUGR of approximately 80 %. The combined EUGR of wind and wave energy in the Bohai Sea, Yellow Sea, ECS, and SCS amounted to 67.41 %, 72.29 %, 86.86 %, and 84.10 %, respectively. The southeastern coastal waters of China exhibited significant complementary and synergistic effects between wind and waves, making them suitable for the joint utilization of wind and wave energy. The distribution and evolution of wind and waves in China's offshore varied due to diverse climate conditions prevailing in different regions. From high to low latitudes, the Bohai Sea was mainly controlled by AO, while the Yellow Sea was jointly affected by AO and AMO; The ECS and SCS were mainly affected by AMO and Niño 3.4, respectively. During El Niño/La Niña years, the SCS exhibited a decrease/increase in WS and H s , with a lag of ∼3 months in response to ENSO. The variation amplitude of WS and H s could reach 3.92 m/s and 1.15 m, respectively. [ABSTRACT FROM AUTHOR]

The interaction between soil moisture (SM) and vegetation dynamics has been proven in previous studies. In situ measurements have provided reliable data to investigate and validate the time effect in different zones, which is important in the hydrology and agriculture fields. There were 845 SM in situ monitoring measurements utilized with the correlation between SM and vegetation across various soil depths and climate zones in China. The impact of climate and teleconnection factors on SM and the leaf area index (LAI) are also discussed. The results indicate that SM increases from northwest to southeast in China. The time lag responses of SM to temperature, precipitation, relative humidity, and sunshine duration are 0–3 days, 3–7 days, 1–3 days, and 3–15 days, respectively. The LAI is most strongly correlated with the climate of the current month. When the LAI leads SM, a negative correlation is observed, whereas a positive correlation is observed when SM leads the LAI. This proves that vegetation growth restricts the increase in SM, and soil drying further restricts the growth of vegetation. There was a response time of 2–4 months between the LAI and SM. The effect of vegetation and deeper SM was significant in the arid zone, while they were coupled with shallow SM in the humid zone. Additionally, the El Niño–Southern Oscillation (ENSO) showed a significant positive correlation with SM in 2015–2016 with signals of 9–14 months. The results provide support for balancing the contradiction between future vegetation restoration and water resource scarcity. [ABSTRACT FROM AUTHOR]

Anthropogenic climate warming is predicted to increase the intensity of global tropical cyclones (TCs) on decadal timescales, known as the 'temperature-TC intensity' paradigm. However, no proxy is currently available to directly quantify TC intensity in the northwestern Pacific region over centennial to millennial timescales. Here, we reconstruct the intensity of past TCs inferred from event-beds detected in two sedimentary systems in eastern China spanning approximately 1910 to 645 yr BP using an instrumental-calibrated technique, thereby encompassing a sufficiently wide range of temperatures to test the paradigm in the time domain. Intriguingly, our two intensity indices, based on flooding depth and wind speed, provide the initial quantitative evidence that TC intensity in eastern China has been anomalously weak since around 1485 ± 45 yr BP, with a reduction of approximately 30 ± 8% in intensity, despite no concurrent temperature shift. This reduction appears to have been pre-conditioned by a combined influence of a weaker El Niño-Southern Oscillation, a stronger Atlantic Meridional Overturning Circulation, and an increased level of Saharan dust. We suggest that the magnitudes of these factors may have crossed a tipping point and have not reverted to their pre-shift levels since that time, resulting in their impact on TC intensity exceeding that of temperature by triggering changes in the oceanic and atmospheric state within the tropical Pacific region where TCs originate. [ABSTRACT FROM AUTHOR]

This paper investigates the impacts of the El Niño Southern Oscillation (ENSO) on various aspects of heat waves (HWs), including frequency, duration, and magnitude, over China during 1961-2014. Results show that El Niño (La Niña) significantly amplifies (weakens) the HW activities in most areas of China. Such influences are particularly strong in southern China. HW activities are enhanced (weakened) during the summers following mature El Niño (La Niña) episodes, with increased (reduced) occurrence of HW events and number of HW days, as well as prolonged (shortened) duration and elevated (decreased) amplitude of such events. These amplifying effects are substantially stronger for severe HWs (i.e., hottest and longest episodes) than for those events of average duration and intensity. Diagnosis by compositing reanalysis data over ENSO events indicates that the atmospheric circulation during the summers following El Niño is characterized by anomalous rising motion over the tropical central Pacific and Indian Oceans, and sinking motion over the western North Pacific (WNP). The anomalous subsidence over the WNP is accompanied by reduced precipitation and condensational heating, as well as anomalous anticyclonic flows in the lower troposphere. El Niño also induces a stronger South Asian high, which can strengthen the WNP anticyclone and subtropical high. These changes provide a favorable environment for the occurrence and sustenance of HWs in China. Analogous arguments apply to changes with the opposite polarity in association with La Niña events. [ABSTRACT FROM AUTHOR]

Coastal wetlands provide valuable ecosystem services and understanding their response to past climatic changes may help predict their possible future responses. In this paper, we obtained records of pollen, algae, sediment grain-size, and other environmental proxies, from a late Holocene sediment core (CFD-E) from the Caofeidian area, on the northwest coast of the Bay of Bohai, China. Our results indicate three major stages of environmental change. During Stage I (3500–2800 cal yr BP), arboreal pollen content was high (mostly >60%), especially for Pinus and Quercus , and the PCA sample scores on Axis 1 were negative indicating that regional vegetation was temperate broadleaved forest and the climate was wet. During Stage II (2800–2350 cal yr BP), the arboreal pollen content decreased substantially (mostly <40%), and the PCA Axis 1 sample scores were positive indicating a decrease in forest vegetation, grassland expansion, and a drier climate. During Stage III (2350–1400 cal yr BP), the arboreal pollen content increased again (mostly >40%), although it remained lower than during Stage I, indicating that forests expanded under a relatively humid climate while the wetland area decreased slightly. Our results also record the 2.8 ka and 2.4 ka events of monsoon weakening, which were characterized by increases in herbaceous pollen (indicating grassland expansion) and the drying of the regional climate. There are several differences in the regional expression of these two climatic events. During the 2.4 ka event, Chenopodiaceae pollen increased substantially (average of 42.0%), indicating the expansion of halophytes; whereas during the 2.8 ka event, an increase in Artemisia indicates the occurrence of a dry climate throughout the region. We suggest that the aridity during the 2.8 ka event was triggered by decreased solar activity and the resulting changes in the El Niño-Southern Oscillation, which weakened the East Asian summer monsoon. However, we suggest that the 2.4 ka event was driven by the weakening of the Atlantic Meridional Overturning Circulation. • Significant increase in halophytic vegetation during 3500–1400 cal yr BP • The 2.8 ka and 2.4 ka events were characterized by climate drying lasting ∼150 years. • During these two events the area of forest decreased and grassland expanded. [ABSTRACT FROM AUTHOR]

[Display omitted] • The drought pattern in China is closely related to the basin distribution and multiple teleconnection factors. • The intensity and frequency of drought in China exhibited an increasing trend. • The ENSO-AO had important positive effects in the major basins in China. • Multiple wavelet coherence helps identify the processes controlling drought changes. Due to increasing global warming and the frequent occurrence of severe drought risk in recent decades, many studies have investigated drought in China. However, the spatiotemporal heterogeneities of droughts are complicated, and a comprehensive analysis of the driving forces has not been thoroughly explored. In this paper, we studied the temporal and spatial patterns of drought in China from 1960 to 2018 and disclosed its relationship with multiple teleconnection factors on different time scales. The results show that (1) Drought in China has exhibited a fluctuating increasing trend over the past 59 years, with a standardized precipitation–evapotranspiration index (SPEI) rate of change of –0.12/10 a, and the most severe droughts occurred during 2000–2010. (2) There was a significant abrupt change in China's meteorological droughts induced by climate change around 1997. (3) The trend in China was characterized by drought in spring and autumn and humidification in winter, while the trend in the Southwest River Basin was characterized by drought. (4) A combination of factors can best explain the drought variations from basin to basin, and the El Niño-Southern Oscillation (ENSO)-Arctic Oscillation (AO) was most commonly the best predictor. The use of multiple wavelet coherence helps to identify the dominant drought change processes. [ABSTRACT FROM AUTHOR]

This paper analyzes the relationship between the 1000-850-hPa layer perturbation potential energy (LPPE) as the difference in local potential energy between the actual state and the reference state and the East Asian summer monsoon (EASM) using reanalysis and observational datasets. The EASM is closely related to the first-order moment term of LPPE (LPPE1) from the preceding March to the boreal summer over three key regions: the eastern Indian Ocean, the subtropical central Pacific, and midlatitude East Asia. The LPPE1 pattern (−, +, +), with negative values over the eastern Indian Ocean, positive values over the subtropical central Pacific, and positive values over East Asia, corresponds to negative LPPE1 anomalies over the south of the EASM region but positive LPPE1 anomalies over the north of the EASM region, which lead to an anomalous downward branch over the southern region but an upward branch over the northern region. The anomalous vertical motion affects the local meridional circulation over East Asia that leads to a southwesterly wind anomaly over East Asia (south of 30°N) at 850 hPa and anomalous downward motion over 100°-120°E (along 25°-35°N), resulting in a stronger EASM, more kinetic energy over the EASM region, and less boreal summer rainfall in the middle and lower reaches of the Yangtze River valley (24°-36°N, 90°-125°E). These LPPE1 anomalies in the eastern Indian Ocean and subtropical central Pacific appear to be connected to changes in local sea surface temperature through the release of latent heat. [ABSTRACT FROM AUTHOR]

The westerly circulation and the monsoon circulation are the two major atmospheric circulation systems affecting the middle latitudes of the Northern Hemisphere (NH), which have significant impacts on climate and environmental changes in the middle latitudes. However, until now, people's understanding of the long-term paleoenvironmental changes in the westerly- and monsoon-controlled areas in China's middle latitudes is not uniform, and the phase relationship between the two at different time scales is also controversial, especially the exception to the "dry gets drier, wet gets wetter" paradigm in global warming between the two. Based on the existing literature data published, integrated paleoenvironmental records, and comprehensive simulation results in recent years, this study systematically reviews the climate and environmental changes in the two major circulation regions in the mid-latitudes of China since the Middle Pleistocene, with a focus on exploring the phase relationship between the two systems at different time scales and its influencing mechanism. Through the reanalysis and comparative analysis of the existing data, we conclude that the interaction and relationship between the two circulation systems are relatively strong and close during the warm periods, but relatively weak during the cold periods. From the perspective of orbital, suborbital, and millennium time scales, the phase relationship between the westerly and Asian summer monsoon (ASM) circulations shows roughly in-phase, out-of-phase, and anti-phase transitions, respectively. There are significant differences between the impacts of the westerly and ASM circulations on the middle-latitude regions of northwest China, the Qinghai–Tibet Plateau, and eastern China. However, under the combined influence of varied environmental factors such as BHLSR (boreal high-latitude solar radiation), SST (sea surface temperature), AMOC (north Atlantic meridional overturning circulation), NHI (Northern Hemisphere ice volume), NAO (North Atlantic Oscillation), ITCZ (intertropical convergence zone), WPSH (western Pacific subtropical high), TIOA (tropical Indian Ocean anomaly), ENSO (El Niño/Southern Oscillation), CGT/SRP (global teleconnection/Silk Road pattern), etc., there is a complex and close coupling relationship between the two, and it is necessary to comprehensively consider their "multi-factor's joint-action" mechanism and impact, while, in general, the dynamic mechanisms driving the changes of the westerly and ASM circulations are not the same at different time scales, such as orbital, suborbital, centennial to millennium, and decadal to interannual, which also leads to the formation of different types of phase relationships between the two at different time scales. Future studies need to focus on the impact of this "multi-factor linkage mechanism" and "multi-phase relationship" in distinguishing the interaction between the westerly and ASM circulation systems in terms of orbital, suborbital, millennium, and sub-millennium time scales. [ABSTRACT FROM AUTHOR]

As one of the natural disasters, drought has caused a large amount of financial loss in the past few centuries. It is quite essential to reveal the variation of extreme drought event in Wei River Basin (WRB) of China. This paper investigated the change patterns of extreme drought event using Standardized Precipitation Evapotranspiration Index (SPEI). Furthermore, the SPEI is predicted by combining different influencing factors in the WRB using Long Short-Term Memory (LSTM) model. The spatiotemporal variation characteristics were examined using non-parametric Mann-Kendall test, and the nonlinear relationships between El Niño-Southern Oscillation (ENSO) and SPEI were quantified using wavelet coherence analysis (WTC). Results showed that midland of the WRB have the highest probability of extreme drought events. Meanwhile, changes in SPEI in the northeast were more erratic than in other regions. The area with extreme drought had increased at a rate of 2.4% per decade. The prediction result of SPEI-24 was the best by LSTM model, and the prediction result of SPEI-3 was the worst. The R-square between the predicted value and the actual value of SPEI-24 is 0.87. The results help to realize the characteristics of extreme drought in the last hundreds of years, which can provide scientific basis and reference for drought emergency response and management in the WRB. [ABSTRACT FROM AUTHOR]

The El Niño/Southern Oscillation (ENSO) is a dominant mode of climate variability influencing temperature and precipitation in distant parts of the world. Traditionally, the ENSO influence is assessed considering its amplitude. Focusing on its quasioscillatory dynamics comprising multiple time scales, we analyze causal influence of phases of ENSO oscillatory components on scales of precipitation variability in eastern China, using information-theoretic generalization of Granger causality. We uncover the causal influence of the ENSO quasibiennial component on the precipitation variability on and around the annual scale, while the amplitude of the precipitation quasibiennial component is influenced by the low-frequency ENSO components with the periods around 6 years. This cross-scale causal information flow is important mainly in the Yellow River basin, while in the Yangtze River basin the causal effect of the ENSO amplitude is dominant. The presented results suggest that in different regions different aspects of ENSO dynamics should be employed for prediction of precipitation. [ABSTRACT FROM AUTHOR]

Atmosphere clearness is the single most essential parameter determining surface solar radiation. However, few studies have investigated the interannual variations in China's atmosphere clearness and the impacts of El Niño–Southern Oscillation on it. This study aims to fill the knowledge gap by calculating the clearness index using the China Meteorological Forcing Dataset version 1.7 and then analyzing the correlations between the interannual anomaly and the Niño-3.4 index. The results show that there is a significantly negative correlation in the southeastern coastal regions, northern Xinjiang, northeastern Xizang, and areas from northern Hebei to middle Inner Mongolia. In these areas, the higher the ENSO index, the lower the clearness index, and, coincidingly, positive precipitation anomalies are reported in previous studies. The impacts of El Niño and La Niña vary with seasons. The ENSO events have generally opposite impacts in the seasons other than summer. El Niño tends to decrease the clearness index, while La Niña tends to decrease the atmosphere clearness in most territories of China. The impacts are different in the places of statistical significance. The negative impacts of El Niño are significant in the southeastern coastal regions of China in winter and in northeast China in autumn. The positive impacts of La Niña are significant in the southwestern and northeastern China in the autumn. In these seasons, ENSO's impacts scale with the strength of the event. Stronger events amplify the magnitude of the anomalies, while the spatial patterns of the anomalies are kept almost invariant. In summer, ENSO's impacts exhibit different characteristics than in the other seasons and between the El Niño and La Niña events. For the El Niño events, the impacts are insignificant in most territories of China, even for the strong ones. La Niña has a larger influence on the summertime clearness than El Niña, and the spatial pattern of the La Niña's impacts varies with the event strength. The anomalies during strong La Niña events have a tripolar pattern with a positive anomaly in south and north China and a negative anomaly in between. The pattern suggests that the relationship between the clearness index and precipitation is different during strong La Niña events. These findings would provide valuable insights into the interannual variations of atmosphere clearness in China and could be clues to further investigation. The revealed impacts of El Niño–Southern Oscillation should be important for developing solar energy. [ABSTRACT FROM AUTHOR]

This study develops a quantitative climatology of water vapour exchange between the atmospheric boundary layer (ABL) and free troposphere (FT) over eastern China. The exchange flux is estimated for January, April, July and October over 7 years based on a water vapour budget equation using simulated meteorological data. The spatiotemporal characteristics and occurrence mechanism of ABL–FT water vapour exchange and its relationship with the El Niño–Southern Oscillation (ENSO) are revealed: (1) the vertical exchange flux varies regionally and seasonally, with downward transport to maintain ABL moisture during winter and autumn in the northern region and persistent output to humidify the FT in the southern region, particularly in summer. Additionally, the vertical exchange flux is also topographic dependent. (2) The vertical motion at the ABL top, which is produced by the dynamic forcing of the terrain on synoptic winds, is the dominant mechanism for the water vapour vertical exchange over the long-term average. The evolution of the vertical exchange flux within 1 d scale is driven by the ABL diurnal cycle. (3) The interannual variation of water vapour vertical exchange is correlated with ENSO. A triple antiphase distribution with negative–positive–negative anomalies from north to south exists in La Niña years (and vice versa in El Niño years), which corresponds to the spatial pattern of anomalous precipitation. This phenomenon is mainly due to the alteration of vertical velocity and water vapour content at the ABL top varying with ENSO phases. These results provide new insight into understanding the atmospheric water cycle. [ABSTRACT FROM AUTHOR]

The Indian Ocean basin (IOB) mode is the dominant mode of the interannual sea surface temperature (SST) variability in the Indian Ocean, with the Indian Ocean dipole (IOD) as the second mode. An IOB event normally occurs after an El Niño or a concurrent IOD–El Niño event, the dynamics of which are traditionally believed as forced by ENSO through the Walker circulation anomalies over the tropical Indian Ocean. A strong IOB in 2020 took place after the strongest 2019 IOD on record but independent of El Niño, which challenges the traditional atmospheric bridge dynamics of the IOB event. In this study, the dynamics of the 2020 IOB event are investigated using the numerical seasonal climate prediction system of the National Marine Environmental Forecasting Center of China. It is found that the initialization of the Indian Ocean subsurface temperature during the 2019 IOD event has led to the outburst of the 2020 IOB event successfully, the dynamics of which are the propagation and the western boundary reflection of the equatorial and off-equatorial Rossby waves, inducing heat content recharge over the tropical Indian Ocean upper thermocline. In comparison, experiments of SST initialization over the tropical Indian Ocean, with the subsurface temperature in a climatological state, were unable to reproduce the onset of the 2020 IOB event, suggesting that the local air–sea interaction within the Indian Ocean basin is of secondary importance. The numerical experiments suggest that the thermocline ocean wave dynamics play an important role in forcing the IOB event. The revealed thermocline dynamics are potentially useful in climate prediction associated with IOB events. [ABSTRACT FROM AUTHOR]

Based on the 30-year global hourly sea surface temperature (SST) dataset (MLSST) produced by the National Marine Environmental Forecasting Center, Ministry of Natural Resources of China, we analyzed the variability of diurnal sea surface temperature amplitude (DSST) of the tropical Indian Ocean at multiple time scales, as well as its influencing factors. The results show that the DSST in the Arabian Sea, Bay of Bengal, and equatorial Indian Ocean exhibits a bimodal seasonal variation with a semi-annual cycle, while the DSST in the southern Indian Ocean shows an annual cycle. The seasonal variation of DSST is mainly influenced by factors such as sea surface wind speed, shortwave solar radiation, and precipitation. The DSST in the equatorial Indian Ocean is generally higher during El Niño years compared to La Niña years. At the intraseasonal scale, the large standard deviation of DSST in boreal winter is mainly distributed in the southern hemisphere, while the large standard deviation of DSST in boreal summer shifts northward. The intraseasonal variation amplitude of DSST in boreal winter of the tropical Indian Ocean is greater than that in boreal summer. The DSST in the tropical Indian Ocean exhibits significant variation characteristics at multi-time scales. This study provides reference for numerical simulation of air-sea interaction patterns in the tropical Indian Ocean, as well as improvement of short-term climate prediction. [ABSTRACT FROM AUTHOR]

The rainy seasons in the Yangtze River valley (called Meiyu) and North China represent two main stages with the northward advance of the East Asian summer monsoon. This study investigates the precipitation prediction skills between these two rainy seasons using the S2S hindcast data from the European Centre for Medium-Range Weather Forecast (ECMWF) during 2002–2021. Meiyu exhibits higher precipitation forecast skill compared to the rainy season in North China. In particular, the forecast skill is more pronounced in the southeast region during the Meiyu, while it has negative performance in central regions of the rainy season in North China. Precipitation patterns during the Meiyu are strongly influenced by the single-blocking system in the high latitude extending from the east of Lake Baikal to the Sea of Okhotsk, as well as the subtropical high at 500 hPa geopotential height in the low latitude. For the rainy season in North China, anomalies in the 500 hPa geopotential height over northeast China has a significant impact on the precipitation according to reanalysis data. The forecast skill of precipitation differs between the two rainy seasons, as well as their associared biases. The model biases are attribute to both circulation simulation and its influence on precipitation. Specifically, the prediction skills of circulation in the low latitudes are high during the Meiyu, and the relationship between circulation and precipitation is well captured. However, the prediction of circulations in the high latitude shows lower skill. During the rainy season in North China, the prediction skills for circulation in key areas are relatively high, but the relationship between circulation in key areas and precipitation is not captured, or may even exhibite an opposite relationship. Meanwhile, the model circulations at different latitudes have different responses to the El Niño state, with more biases observed in the high latitudes. In summary, the decline in prediction skills with the northward advance of the East Asian summer monsoon emphasizes the crucial role of predictability in the high latitudes. [ABSTRACT FROM AUTHOR]

The first rainy season (FRS) in South China from late-spring to early-summer represents the beginning of the summer monsoon rainy season over eastern China. This study investigates the interannual relationship between the South Pacific meridional sea surface temperature (SST) dipole (SPMD) and the concurrent FRS precipitation anomalies over South China during April–June (AMJ) without El Niño/Southern Oscillation (ENSO) impact. During AMJ, after removing the concurrent ENSO signal through the linear regression, the first empirical orthogonal function (EOF) mode of SST anomalies in the South Pacific exhibits a meridional dipole with warming in the tropical southeastern Pacific and cooling in mid-latitudes of the South Pacific. The first EOF mode is referred to as the SPMD pattern. The off-equatorial enhanced diabatic heating associated with the northeastern pole of the SPMD triggers low-level cross-equatorial northerlies in the tropical north central Pacific (TNCP) through the Matsuno–Gill type response. The anomalous northerly and its associated TNCP SST cooling lead to a Northwest Pacific anomalous anticyclone (NWP-AAC) via the wind-evaporation-SST feedback. The atmospheric general circulation model sensitivity experiments further suggest that the SPMD can induce the NWP-AAC directly or collaboratively with the TNCP SST cooling. Additionally, anomalous moisture can be transported from the tropical western Pacific into South China, giving rise to enhancement of the FRS precipitation. The Liang–Kleeman information flow for causality analysis and ensemble mean of 30-member atmospheric model simulation results further suggest a robust physical pathway that the SPMD is related to the FRS precipitation over South China when ENSO absents. Our results may deepen the understanding of interannual rainfall variability in South China in non-ENSO years. [ABSTRACT FROM AUTHOR]

The abundant precipitation over Southern China during the pre–flood season (PFS) [i.e., April–June (AMJ)] has important socioeconomic impacts on this densely populated region. Using observational and reanalyzed datasets, this study explores how El Niño affected the subsequent PFS precipitation over Southern China during 1961–2020. The results show that the El Niño–related anomalies in sea surface temperature forced a northwestern Pacific anomalous anticyclone (NPAAC) in the decaying AMJ. This NPAAC featured southwesterly wind anomalies in its northwestern flank, which could transport moisture from the South China Sea, and accompanying the NPAAC there was abnormal descending motion over the tropical western Pacific, resulting in weakened regional Hadley circulation with abnormal ascending motion over subtropical East Asia. Before the 1990s, this abnormal ascending motion was located mainly to the east of Southern China with insignificant impacts on the PFS precipitation there. In contrast, after the early 1990s, El Niño–related warm sea surface temperature anomalies were stronger and longer-lasting with westward extension. This enhanced the NPAAC with a decadal westward extension, and consequently, the anomalous regional Hadley circulation was more evident over Southern China after the early 1990s during the El Niño decaying AMJ, causing strong abnormal upward motion and excessive precipitation there. The present results emphasize an enhancing influence of El Niño on the subsequent PFS precipitation over Southern China since the early 1990s, offering better understanding of the interannual precipitation variability over Southern China and with important implications for regional seasonal climate prediction. Significance Statement: The precipitation over Southern China during the pre–flood season (PFS) contributes between 40% and 50% of the local annual precipitation, with severe floods occurring frequently and tremendous socioeconomic impacts on the region, including on its agriculture, water resources, food security, ecosystems, disaster mitigation, infrastructure construction, and human health. This study reveals a decadal enhancement in the effect of El Niño on the subsequent PFS precipitation over Southern China since the early 1990s. This is ascribed to a decadal enhancement of El Niño–related warm sea surface temperature anomalies over the equatorial central Pacific, as a result of El Niño warming occurring more frequently over the central Pacific against the backdrop of global warming. To the extent that the central Pacific El Niño events would occur even more frequently for the projected future warming scenarios, a stronger effect of El Niño on the PFS precipitation over Southern China would be expected, implying potentially enhanced seasonal predictability of the regional climate in the future. [ABSTRACT FROM AUTHOR]

Different from the traditional definition of the South China Sea western boundary current (SCSWBC), in this paper, only the southwestward and southward currents along the northern and western slopes in the SCS, which are closely associated with the basin-wide wind stress curl, are defined as the SCSWBC, while the flows on the southwestern shelf driven directly by the local wind stress are regarded as part of the shelf circulation. Using a new reanalysis dataset of the SCS in conjunction with the in situ and remote sensing data, the main features and variability of the SCSWBC from 1992 to 2011 were studied. Dictated by the prevailing monsoonal winds and in- and outflows, the SCSWBC in winter extended the full length of the western slope and reached its maximum intensity off the southeast coast of Vietnam, while in summer the main body of the SCSWBC was limited to the northern half of the western slope and merged with the northward coastal current to form the Vietnam Offshore Current (VOC) at about 12° N. Moreover, the respective seasonal patterns of the SCSWBC showed pronounced interannual variations in its structure, including the axis, the width, and the maximum depth. The strength of the SCSWBC, with the transport of −11.8 ± 3.5 Sv in winter and −3.0 ± 1.6 Sv in summer off the central coast of Vietnam, also varied significantly from year to year. It was demonstrated that the monsoonal forcing over the SCS, the interannual variability of which was closely associated with El Niño events, played an important role in modulating the interannual variability of the SCSWBC, whereas the influence from the upper-layer Luzon Strait transport was secondary. [ABSTRACT FROM AUTHOR]

Wang, X.; Jiang, R.; Xie, J.; Zhao, Y.; Li, F., and Zhu, J., 2019. Multiscale variability of precipitation and their teleconnection with large-scale climate anomalies: A case study of Xi'an city, China. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 417–426. Coconut Creek (Florida), ISSN 0749-0208. The changes of precipitation affect the urban rainstorm waterlogging and water resources management, which have important influences on the sustainable development of society. The primary objective of the paper is to provide theoretical basis for local water resources management and disaster prevention and reduction by analyzing the multiscale variability of precipitation and their teleconnection with large-scale climate anomalies in Xi'an city of China. The change characteristics of precipitation and extreme precipitation indices were investigated using Mann-Kendall test, Spearman's rank correlation and wavelet analysis. The cross wavelet transform and wavelet coherence were used to explore the correlations between the precipitation and large-scale teleconnection indices such as Arctic Oscillation (AO), Southern Oscillation Index (SOI), El Niño-Southern Oscillation (ENSO) and sunspot. Results indicate that: the precipitation was mainly concentrated in summer, followed by autumn. The annual, seasonal and monthly precipitation except June and August had decreasing trends, and the magnitudes of precipitation decrease were more pronounced in spring, April and November. The change patterns varied for extreme precipitation indices. The temporal variation in extreme precipitation indices indicated that the extreme precipitation events had mainly increased during 1971-1990 and 1991-2017, and decreased during 1951-1970 and 1951-2017, especially, increased more pronounced during 1991-2017 and decreased more pronounced during 1951-1970. The precipitation exhibited a fluctuant change from increase to decrease, then increase to decrease and finally increase trends, and there was an abrupt change point in 1965. The annual precipitation had statistically significant cycles of 3-5 year and 7-10 year at 5% significance level. The large-scale teleconnection indices affected the precipitation in Xi'an city. The phase differences between precipitation and teleconnection indices including AO and SOI were in-phase dominated, and anti-phase dominated between precipitation and teleconnection indices including ENSO and sunspot, indicating that the AO and SOI exerted positive climate impacts on the precipitation and vice-versa for ENSO and sunspot. [ABSTRACT FROM AUTHOR]

The 4.2 ka event was a period of global drought and climate cooling linked to the widespread disruption of Neolithic culture. However, the detailed climatic changes during this period are not completely understood. In this paper, we report a high-resolution pollen record for the Dayanghu wetland in the Zhejiang region of southeastern China, which we use to infer mean annual precipitation (MAP) fluctuations during the period spanning 4600–4000 calendar years before present (cal. yr BP). There was a long-term trend of decreasing MAP during this interval, consistent with weakening of the East Asian Summer Monsoon since the mid-Holocene. This trend was punctuated by episodes of relatively high MAP at 4350–4320, ca. 4260, and 4220–4200 cal. yr BP, and extreme droughts at 4200 and 4150 cal. yr BP. We propose that solar activity promoted El Niño events and contributed to dramatic MAP fluctuations in the Dayanghu wetland. La Niña events and negative-phase intervals of the Pacific Decadal Oscillation may have been responsible for the extreme drought at 4200–4150 cal. yr BP. In summary, we propose a close relationship between MAP and solar forcing, with short-term enhanced solar activity increasing the intensity of the East Asian Summer Monsoon and contributing to increasing decadal variability in the inner tropical Pacific, which ultimately leads to increased precipitation variability in southeast China. The results improve our understanding of the detailed climatic features of the 4.2 ka event. • High-resolution pollen record for ca. 4.2 ka for the Zhejiang region, China. • Pollen-based mean annual precipitation was quantitatively reconstructed. • Long-term droughts tended to occur during 4600–4000 cal. yr BP. • La Niña-dominated ENSO contributed to a catastrophic drought at 4200–4150 cal. yr BP. [ABSTRACT FROM AUTHOR]

This study reveals that South China precipitation (SCP) anomalies tend to persist well from winter to the following spring after the late 1990s, favoring long-lasting drought or flood events over South China. Mechanism analysis indicates that the interdecadal changes in El Niño-Southern Oscillation (ENSO) and the preceding November central Asian snow cover could contribute to the increased persistence of winter-to-spring SCP anomalies. ENSO has a stable impact on winter SCP, whereas its impact on spring SCP is significantly enhanced after the late 1990s. With a weakened intensity and faster decay rate in the recent two decades, the ENSO-related spring SST anomalies over the tropical Pacific are relatively weaker, inducing a weakened and more southward-located western North Pacific anticyclone. This further leads to an interdecadal migration of the spring rainfall belt anomaly, consequently favoring the persistence of winter-to-spring SCP anomalies after the late 1990s. Additionally, the impacts of November central Asian snow cover on winter and spring SCP are both strengthened after the late 1990s. In the most recent two decades, the snow-cover-related cooling effect has become stronger, which induces winter cyclonic anomalies over Lake Baikal, favoring increased winter SCP. In addition, increased snow cover excites upward-propagating waves from the troposphere to the stratosphere, consequently weakening the stratospheric polar vortex. In spring, the stratospheric polar vortex signals propagate downward and result in a negative Arctic Oscillation in the troposphere, favoring more spring SCP. Therefore, central Asian snow cover is also conductive to the persistence of winter-to-spring SCP anomalies after the late 1990s. [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]

Accelerated sea level rise is placing coastal communities in a vulnerable position; however, the processes underlying sea level acceleration in China remain uncertain. In this study, we examine the sea level acceleration and its contributors over the China Seas. We calculate acceleration along the Chinese coast using satellite altimetry and tide gauge records. During the satellite altimetry era, sea level acceleration from tide gauge records varies across all stations, reaching up to 0.30 ± 0.20 mm/yr2, while satellite altimetry could underestimate/overestimate the sea level acceleration in most locations. Acceleration near the coast, except in the Bohai Sea, is mainly driven by changes in the mass component. In contrast, for the open ocean, changes in steric sea level are the main contributor to sea level acceleration. The evolution of spatial acceleration patterns over the China Seas reveals that the ENSO and PDO variabilities dominate the changing patterns of sea level acceleration in the open ocean, including the Philippine Sea through steric sea level, and changes in most coastal locations are due to the non-steric component. [ABSTRACT FROM AUTHOR]

There is a continuous and relatively stable rainy period every spring in southern China (SC). This spring precipitation process is a unique weather and climate phenomenon in East Asia. Previously, the variation characteristics and associated mechanisms of this precipitation process have been mostly discussed from the perspective of seasonal mean. Based on the observed and reanalysis datasets from 1982 to 2021, this study investigates the diversity of the interannual variations of monthly precipitation in spring in SC, and focuses on the potential influence of the tropical sea surface temperature (SST) anomalies. The results show that the interannual variations of monthly precipitation in spring in SC have significant differences, and the correlations between each two months are very weak. All the interannual variations of precipitation in three months are related to a similar western North Pacific anomalous anticyclone (WNPAC), and the southwesterlies at the western flank of WNPAC bring abundant water vapor for the precipitation in SC. However, the WNPAC is influenced by tropical SST anomalies in different regions each month. The interannual variation of precipitation in March in SC is mainly influenced by the signal of El Niño-Southern Oscillation, and the associated SST anomalies in the equatorial central-eastern Pacific regulate the WNPAC through the Pacific-East Asia (PEA) teleconnection. In contrast, the WNPAC associated with the interannual variation of precipitation in April can be affected by the SST anomalies in the northwestern equatorial Pacific through a thermally induced Rossby wave response. The interannual variation of precipitation in May is regulated by the SST anomalies around the western Maritime Continent, which stimulates the development of low-level anomalous anticyclones over the South China Sea and east of the Philippine Sea by driving anomalous meridional vertical circulation. [ABSTRACT FROM AUTHOR]

The winter precipitation over South China (SCWP) can exert great impacts on the local ecosystem and human livelihood. Previous studies suggested that the inter-annual variability of SCWP can be affected by the El Niño-Southern Oscillation (ENSO) via the Northwest Pacific anticyclone (NWPAC). The present study investigates the role of the India–Burma Trough (IBT) in mediating the teleconnection between ENSO and the SCWP. During the El Niño mature winter, the slowdown of Walker circulation is evident over the tropical Indian Ocean (TIO). The low-level easterly wind anomaly is pronounced from the warm pool to the western TIO, which turns into the westerly wind anomaly over the northern TIO basin and then enhances IBT. Meanwhile, the Kelvin wave in the upper troposphere stimulated by El Niño propagates eastward toward Indian Ocean and induces the tropospheric warming over TIO. The resultant increase of the meridional temperature gradient leads to the southward shift of the westerly jet stream which favors the strengthening of IBT and the increase of SCWP. It is further shown that the IBT change is unclear in La Niña. This nonlinear feature can be largely attributed to the asymmetry in both ENSO amplitude and ENSO-related circulation anomalies. The present findings highlight the role of IBT, in addition to the well-known NWPAC, in bridging ENSO and SCWP. [ABSTRACT FROM AUTHOR]

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El Niño Modoki, similar to but different from canonical El Niño, has been observed since the late 1970s. In this paper, using HadISST and NCEP/NCAR wind data, we analyze the relationship between El Niño Modoki and Sea Surface Temperature (SST) in the offshore area of China and its adjacent waters for different seasons. Our results show a significant negative correlation between El Niño Modoki in summer and SST in autumn in the offshore area of China and its adjacent waters, particularly for regions located in the east of the Kuroshio. It is also found that during El Niño Modoki period, anomalous northerlies prevail over the regions from the northern part of the Philippines to the offshore area of China, indicating that the northerlies are unfavorable for the transport of warm water from the western tropical Pacific to the mid-latitude area. Consequently, El Niño Modoki in summer may play a substantial role in cold SST anomalies in the offshore area of China and its adjacent waters in autumn through the influence of the Kuroshio, with a lagged response of the ocean to the atmospheric wind field. [ABSTRACT FROM AUTHOR]

Based on their opposite influences on rainfall in southern China during boreal fall, this paper classifies El Niño Modoki into two groups: El Niño Modoki I and II, which show different origins and patterns of SST anomalies. The warm SST anomalies originate in the equatorial central Pacific and subtropical northeastern Pacific for El Niño Modoki I and II, respectively. Thus, El Niño Modoki I shows a symmetric SST anomaly distribution about the equator with the maximum warming in the equatorial central Pacific, whereas El Niño Modoki II displays an asymmetric distribution with the warm SST anomalies extending from the northeastern Pacific to the equatorial central Pacific. Additionally, the warm SST anomalies in the equatorial central Pacific extend farther westward for El Niño Modoki II than for El Niño Modoki I. Similar to the canonical El Niño, El Niño Modoki I is associated with an anomalous anticyclone in the Philippine Sea that induces southwesterly wind anomalies along the south coast of China and carries the moisture for increasing rainfall in southern China. For El Niño Modoki II, an anomalous cyclone resides east of the Philippines, associated with northerly wind anomalies and a decrease in rainfall in southern China. The canonical El Niño and El Niño Modoki I are associated with a westward extension of the western North Pacific subtropical high (WNPSH), whereas El Niño Modoki II shifts the WNPSH eastward. Differing from canonical El Niño and El Niño Modoki I, El Niño Modoki II corresponds to northwesterly anomalies of the typhoon steering flow, which are unfavorable for typhoons to make landfall in China. [ABSTRACT FROM AUTHOR]

The inter-annual variability of the tropical Pacific Subsurface Ocean Temperature Anomaly (SOTA) and the associated anomalous atmospheric circulation over the Asian North Pacific during the El Niño-Southern Oscillation (ENSO) were investigated using National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) atmospheric reanalysis data and simple ocean data simulation (SODA). The relationship between the ENSO and the climate of China was revealed. The main results indicated the following: 1) there are two ENSO modes acting on the subsurface tropical Pacific. The first mode is related to the mature phase of ENSO, which mainly appears during winter. The second mode is associated with a transition stage of the ENSO developing or decaying, which mainly occurs during summer; 2) during the mature phase of El Niño, the meridionality of the atmosphere in the mid-high latitude increases, the Aleutian low and high pressure ridge over Lake Baikal strengthens, northerly winds prevail in northern China, and precipitation in northern China decreases significantly. The ridge of the Ural High strengthens during the decaying phase of El Niño, as atmospheric circulation is sustained during winter, and the northerly wind anomaly appears in northern China during summer. Due to the ascending branch of the Walker circulation over the western Pacific, the western Pacific Subtropical High becomes weaker, and south-southeasterly winds prevail over southern China. As a result, less rainfall occurs over northern China and more rainfall over the Changjiang River basin and the southwestern and eastern region of Inner Mongolia. The flood disaster that occurred south of Changjiang River can be attributed to this. The La Niña event causes an opposite, but weaker effect; 3) the ENSO cycle can influence climate anomalies within China via zonal and meridional heat transport. This is known as the 'atmospheric-bridge', where the energy anomaly within the tropical Pacific transfers to the mid-high latitude in the northern Pacific through Hadley cells and Rossby waves, and to the western Pacific-eastern Indian Ocean through Walker circulation. This research also discusses the special air-sea boundary processes during the ENSO events in the tropical Pacific, and indicates that the influence of the subsurface water of the tropical Pacific on the atmospheric circulation may be realized through the sea surface temperature anomalies of the mixed water, which contact the atmosphere and transfer the anomalous heat and moisture to the atmosphere directly. Moreover, the reason for the heavy flood within the Changjiang River during the summer of 1998 is reviewed in this paper. [ABSTRACT FROM AUTHOR]

The findings of the study reported in this paper show that, during ENSO decaying summers, rainfall and circulation anomalies exhibit clear subseasonal variation. Corresponding to a positive (negative) December--February (DJF) Niñño-3.4 index, a positive (negative) subtropical rainfall anomaly, with a southwest--northeast tilt, appears in South China and the western North Pacific (WNP) in the subsequent early summer (from June to middle July) but advances northward into the Huai River Basin in China as well as Korea and central Japan in late summer (from late July to August). Concurrently, a lower-tropospheric anticyclonic anomaly over the WNP extends northward from early to late summer. The seasonal change in the basic flows, characterized by the northward shift of the upper-tropospheric westerly jet and the WNP subtropical high, is suggested to be responsible for the differences in the above rainfall and circulation anomalies between early and late summer by inducing distinct extratropical responses even under the almost identical tropical forcing of a precipitation anomaly in the Philippine Sea. A particular focus of the study is to investigate, using station rainfall data, the subseasonal variations in ENSO-related rainfall anomalies in eastern China since the 1950s, to attempt to examine their role in weakening the relationship between the ENSO and summer mean rainfall in eastern China since the late 1970s. It is found that the ENSO-related rainfall anomalies tend to be similar between early and late summer before the late 1970s, that is, the period characterized by a stronger ENSO--summer mean rainfall relationship. After the late 1970s, however, the anomalous rainfall pattern in eastern China is almost reversed between early and late summer, resulting accordingly in a weakened relationship between the ENSO and total summer rainfall in eastern China. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the relationship between flood/drought change in the Taihu Lake basin (TLB) and ENSO is investigated based on reconstructed flood/drought rank series (FD) and NINO-3.4 SST (DJF) data from 1857 to 2003. With the aid of empirical mode decomposition (EMD) method, the paper reveals that FD series and ENSO both contain strong inter-annual, decadal, multi-decadal and centennial signals, and have quite similar periodicities. The EMD method also obtains a monotonic trend for both series: the trend of FD series is upward, which suggests that flood trend is significant, and the trend of NINO-3.4 SST is also upward showing an increase of El Nino events. Continuous wavelet transform obtains similar oscillations for FD and NINO-3.4 SST series with those of EMD method. The results of cross wavelet and wavelet coherence suggest that there was stable in-phase relation between FD and NINO-3.4 SST from 1857 to 1950s, while this in-phase relation is not clear during recent decades. This conclusion is also verified by χ 2 test. These findings indicate weakening linkage between ENSO and flood/drought disasters in the TLB, which must be taken into account in the prediction of flood and drought disasters in the study area. [Copyright &y& Elsevier]

In recent years, more and more record-breaking extreme weather/climate events have been reported from the Asian monsoon region, which have caused tremendous loss of property and lives. In this paper, we analyzed the Asian summer monsoon (ASM) variability during the Holocene and evaluated future climate extremes in monsoonal China from a paleoclimatic view. We found a significant regime transition to more chaotic fluctuations, with enhanced decadal variability of the ASM since 6.6 ka BP. We suggested the gradual intensification of ENSO was responsible for enhancing the ASM variability since the late mid-Holocene. If the observed relationship of monsoon mean intensity, ENSO and decadal variability of the ASM in the past 11.2 ka continue to exist, enhanced decadal variability of ASM in the future warming world will be expected. As a result, the intensification of daily precipitation extremes, superimposed on enhanced decadal variability of ASM, might make the record-breaking extremes more frequent in the future, increasing the risk of climate-related disasters in China. [ABSTRACT FROM AUTHOR]

The vegetation drought phenomenon will reduce the amount of water available to the vegetation system, change the ecological and hydrological cycles of plants, and affect the aquatic and terrestrial ecosystem in various forms. Therefore, research on the dynamic variation and driving mechanism of vegetation drought will help us recognize and predict the response of vegetation under drought stress conditions, implement appropriate policy measures to deal with the drought crisis, and provide technical support for implementing vegetation protection and alleviating the increasing risk of vegetation drought. However, the dynamic variation of vegetation drought and its dynamic propagation mechanism are still undefined across China. In this study, the spatio-temporal evolutions and pixel-scaled trends of vegetation drought were analyzed during the period between 1999 and 2020. Additionally, the propagation features were investigated between vegetation drought and meteorological drought. Finally, the relationships between vegetation drought and atmospheric teleconnection were explicitly clarified using multivariate cross wavelet transform technology. The results highlighted five key findings: (1) the vegetation drought presented an overall decreasing trend across China in 1999–2020; (2) the most serious vegetation drought occurred in the year 2000, with the average vegetation condition index (VCI) values ranging from 0.36 to 0.46; (3) vegetation droughts were alleviating at the pixel scale for each season; (4) the propagation time from meteorological drought to vegetation drought was shorter in summer (1.26 months) and longer in winter (2.26 months); and (5) the three-factors combination of Pacific North American (PNA), El Niño-Southern Oscillation (ENSO), and Trans Polar Index (TPI) can satisfactorily explain the variations of vegetation drought. This study sheds new viewpoints into the identification of vegetation drought variation across China, which can also be applied in other areas. [ABSTRACT FROM AUTHOR]

March rainfall over southern China (SC) experiences a significant decrease of the intensity of interannual variation (IIV) around 1996/1997. During 1982–1996, the IIV of March rainfall over southern China (SCMR) are stronger than during 1997–2011, and the interannual variation of SCMR is closely related to sea surface temperature (SST) anomalies. The eastern Pacific El Niño (La Niña) would weaken (strengthen) the Walker circulation, accompanying convergence (divergence) anomalies over tropical eastern Pacific and divergence (convergence) anomalies over western Pacific in the lower level. The divergent wind anomalies blow from western Pacific (SC) to SC (western Pacific) and converge (diverge) over SC, which favors ascending (descending) motions over there. The water vapor convergence (divergence) anomalies and ascending (descending) motions over SC cause more (less) SCMR. Besides, positive (negative) tropical southeastern Indian Ocean SST anomalies are of benefit to the more (less) SCMR by affecting vertical circulation. However, the relation between SCMR and SST anomalies decreases after 1997. During 1997–2011, SCMR experiences the lower IIV period than before. The snow depth over the Eurasia continent has an important impact on the SCMR. The SCMR is negatively correlated with the snow depth from the Siberia to Northeast China, but positively correlated with the snow depth over the Tibetan Plateau (TP). The ground obtains more (less) heat flux with less (more) snow, accompanying positive (negative) outward long wave radiation anomalies and latent heat flux anomalies, which helps to maintain positive (negative) air temperature anomalies over the Siberia to Northeast China. Meanwhile, the ground over TP obtains less (more) heat flux with more (less) snow, favoring negative (positive) air temperature anomalies. The configuration of air temperature and geopotential height dipole anomalies conforms to static equilibrium over East Asia, and favors the cyclone-anticyclone (anticyclone-cyclone) dipole anomalies from the low latitudes to the mid-high latitudes in the upper level, which represents the southward (northward) subtropical upper-level westerly jet over TP, conducive to more (less) SCMR. The external forcings that have impacts on the interannual variation of SCMR experience an interdecadal change before and after 1996/1997. [ABSTRACT FROM AUTHOR]

High-resolution temperature reconstructions in the previous millennium are limited in Northeast Asia, but they are important for assessing regional climate dynamics. Here, we present, for the first time, a 202-year reliable reconstruction of April temperature changes before the millennium volcanic eruption in 946 CE using tree rings of carbonized logs buried in the tephra in Changbai Mountain, Northeast Asia. The reconstructed temperature changes were consistent with previous reconstructions in China and the Northern Hemisphere. The influences of large-scale oscillations (e.g. El Niño–Southern Oscillation, ENSO) on temperature variability were not significantly different between the periods of 745–946 CE preceding the eruption and 1883–2012. However, compared to the palaeotemperature of the previous millennium, the temperature changes were more complex with stronger temperature fluctuations, more frequent temperature abruption, and a weaker periodicity of temperature variance during the last 130 years. These recent changes correspond to long-term anthropogenic influences on regional climate. [ABSTRACT FROM AUTHOR]

The roles of rainfall with various intensities in hydraulic erosion processes are obviously different. In-depth knowledge about the spatiotemporal variation in extreme rainfall erosivity is critical for soil erosion risk assessment and formulation of response measures. In the period of 1961–2020, more than 390,000 erosive rainfall data from 212 meteorological stations were collected to explore the erosion characteristics of different intensities of rainfall erosivity across southern China. The asymmetric characteristic of extreme rainfall erosion was analyzed and expressed by an asymmetric change index (ACI) defined in this study. Correlation analysis was applied to study the impact of global extreme climate events on the ACI. The results showed that different patterns of precipitation had evident asymmetric characteristics in rainfall erosivity, and fewer high-intensity precipitation events contributed to much higher total rainfall erosivity, particularly for rainstorms (≥100 mm). The ACI of the rainfall erosivity exhibited evident spatial heterogeneity; insignificant increasing trends were found in the ACIs for heavy rainfall, torrential, and rainstorm erosivities over the past 60 years. The change rate of ACI varied greatly on both monthly and interdecadal scales, and the ACI of rainstorms showed the maximum linear increasing trend on the long-time scale. There were significantly high correlations between the ACI and erosive rainfall days and the ACI and erosive rainfall (p < 0.01), and the correlation coefficients were relatively higher from May to October, where the precipitation was concentrated. Additionally, the El Niño-Southern Oscillation and tropical cyclones clearly influenced the spatiotemporal distribution of the ACI and rainfall erosivity but were limited to specific periods and regions. These results could provide a reference for extreme soil erosion event monitoring and control in southern China. [ABSTRACT FROM AUTHOR]

Decadal‐scale unforced climate variability associated with low‐frequency ocean (or coupled) modes can be identified within the time‐evolving sea surface temperature (SST) pattern. We seek to find a relationship between 12 well‐known climate modes of variability (El Niño–Southern Oscillation, Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation, etc.), which are reflected in the SST pattern, and decadal trends in downwelling shortwave radiation at Earth's surface (surface solar radiation, surface shortwave radiation [SSR]). The analysis is performed using the pre‐industrial control runs (piControl) of 57 models from the Coupled Model Intercomparison Project—Phase 6. We find that regional SSR trends occur during periods when a climate mode is transitioning and show a mirroring pattern (opposite sign SSR trends) when the mode transitions in the opposite direction. Unforced trends in clear‐sky SSR are mostly driven by SST‐induced water vapor changes, while all‐sky SSR trends show a complex spatial structure with trends of different signs in different regions. Unforced SSR trends are generally weaker in simulations with climatological SSTs. The role of natural aerosols as another potentially relevant factor for SSR variability is briefly addressed and we find that constantly higher aerosol loads result in increased variability for clear‐sky conditions, but not for all‐sky conditions. The results from this study suggest that all‐sky dimming and brightening in different parts of the world are enhanced rather than suppressed by internal variability related to an SST‐pattern with the exception of India and China, where both effects are present. A practical application can be the planning of photovoltaic energy facilities given areas where internal variability is generally smaller or affects SSR in opposite directions. Plain Language Summary: The Earth system (atmosphere, ocean, land, cryosphere, and biosphere) changes not only as a result of anthropogenic or volcanic activities but also as a result of internal processes, also known as background noise. Climate science offers a simplified description of this "noise" by assigning climate indices, which help to describe the larger system with a single time series. More generally, the climate indices are an attempt to describe the temporal evolution of complex modes of variability such as El Niño–Southern Oscillation, Pacific Decadal Oscillation, and Atlantic Multidecadal Oscillation. With the use of climate models, we check how these indices are reflected in the decadal changes of solar radiation reaching Earth's surface, a flux which is mainly affected by clouds, water vapor, and natural and anthropogenic aerosols suspended in the atmosphere. Our results suggest that ocean surface temperature changes, which evolve over a few decades, control cloudiness and water vapor amounts above many land regions. This ocean temperature evolution may result in a naturally induced dimming and brightening of solar radiation over continents. Our findings are relevant for questions involving long‐term changes of the solar radiation reaching the Earth's surface, ranging from physical causes of observed changes to long term planning of photovoltaic energy production. Key Points: Long term trends in annual mean all‐sky and clear‐sky surface solar radiation entail strong changes in major climate indicesAnnual mean surface solar radiation variability is 25%–30% greater for sea surface temperatures (SSTs) that vary in time than for climatological SSTsConstantly higher aerosol loads result in increased variability for clear‐sky conditions, but not for all‐sky conditions [ABSTRACT FROM AUTHOR]

In this paper, we analyze the Holocene record of extreme flood events in the upper Minjiang River valley of the eastern Tibetan Plateau, China. Slackwater deposits (SWDs), the fine-grained sediments of palaeofloods, were identified within debris flow deposits at a tributary mouth and in channel expansions along the bedrock gorge. Eight palaeoflood SWDs were dated to between 6.0 ± 0.9 ka and 4.6 ± 0.9 ka using optically-stimulated luminescence analysis in combination with the minimum age model and represent at least two phases of palaeoflood events. The palaeoflood history in the upper Minjiang River Valley is consistent with the record of the mid-Holocene flood events in the mainstream of the Yangtze River. These mid-Holocene extreme flood events were closely related to strong ENSO activity and variability of the monsoon climate in the eastern Tibetan Plateau. In our study area, minimum palaeoflood discharges were estimated as 6500–7800 m3/s by the step-backwater method. These estimated discharges are less than the values inferred for the outburst flood that occurred in the upper Minjiang River Valley in 1933. Flood-inundation maps show that palaeoflood SWDs were deposited in low-velocity backwater zones. Our palaeoflood reconstructions are important for improving regional records of maximum flood and help to develop risk analysis for rare flood events. • Sedimentary characteristics of palaeoflood records in complex environment were identified. • Palaeoflood discharges were estimated to be 6500–7800 m3/s at the three study sites. • Palaeoflood results redefine the envelope curve of the regional maximum floods. • Response of mid-Holocene (6.0–4.6 ka) extreme flood events to climate variability. • Palaeoflood reconstructions help to develop risk analysis for rare flood events. [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]

As subsystems of the Asian summer monsoon, summer precipitation variations in India and the northern part of eastern China (NEC) are physically connected. This study noted that the connection has been significantly enhanced after 1999 compared to 1979-98, which is due to the strengthened water vapor transportation connection between the two regions. That is associated with interdecadal variations of the combined effects of El Niño-Southern Oscillation (ENSO) and sea surface temperature anomalies (SSTAs) over the tropical Indian Ocean (TIO) on the northwest Pacific subtropical high (NWPSH) and the Indo-Pacific Walker cell. Against the background of La Niña, the strengthened NWPSH and Indo-Pacific Walker cell favor water vapor transport to India and the NEC since 1999. Accordingly, summer precipitation in the two regions increases simultaneously, leading to the enhancement of the summer precipitation teleconnection between them. In addition, the influence of TIO SSTAs and the Indian Ocean dipole (IOD) on Indo-Pacific circulations decreases, which further enhances the relative importance of ENSO on the summer precipitation in the two regions. However, during 1979-98, La Niña SSTAs has weak effects on the NWPSH and Indo-Pacific Walker cell, the negative TIO SSTAs significantly weaken NWPSH, and the negative IOD also obstructs the westward extension of the Indo-Pacific Walker cell. Circulations and water vapor transportation related to the Indian Ocean and NEC summer precipitation are inconsistent, resulting in a weak precipitation teleconnection between them. The above conclusions are also validated by extreme case analysis and CMIP6 models. [ABSTRACT FROM AUTHOR]