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The East Asian summer monsoon (EASM) shows notable change during the summer after El Niño peak. This “delayed” response, however, is variable and difficult to predict. Here, we revisit this issue by separating El Niño decays into early transition and late transition. In the summer after an early transition, the central-to-eastern Pacific evolves into a La Niña condition, with positive rainfall anomaly occurring over most parts of eastern China. In contrast, in the summer after a late transition, the central-to-eastern Pacific sea surface temperature (SST) anomaly remains neutral or slightly above normal; correspondingly, the East Asian rainfall anomaly shows a tripolar structure with positive anomaly over the Yangtze-Huaihe River valley and negative anomalies over northern and southern China. These different rainfall responses are mainly related to different locations of the anomalous anticyclone (AAC) over the western North Pacific (WNP): it is centered at (165°E, 25°N) for late-transition El Niños, but at (135°E, 16°N) for early-transition El Niños. During the late transition, the AAC–SST feedback, identified by the dipole SST mode consisting of WNP cooling and northern Indian Ocean (NIO) warming, mainly works to support the WNP AAC. During the early transition, the AAC–SST feedback is weak and mainly attributed to NIO warming. The strong easterly anomaly over the western equatorial Pacific, which is tied to the central-to-eastern equatorial Pacific cooling and dipole precipitation pattern from western equatorial Pacific to the Maritime Continent, occurs to support the AAC and pulls it equatorward. These distinct responses exist in the last century, and the CMIP5 models can reproduce these distinct responses well except that the models underestimate the AAC–SST feedback for late-transition El Niños. The findings in this study help predict the EASM rainfall in post-El Niño years, but the key is the accurate prediction of the timing of decay.

Westerlies Asia, which includes arid Central Asia (ACA) and arid West Asia (AWA), is characterized by water vapor transport primarily controlled by the westerlies. Recent studies have identified a dipole pattern in hydroclimate variability between ACA and AWA during both the Holocene and modern period. However, it remains unclear whether such a dipole pattern persisted over the past millennium. Our findings demonstrate that the PMIP4 multi-model simulations reveal a dipole precipitation pattern between arid Central Asia and arid West Asia over the past millennium. During the Little Ice Age (LIA), annual precipitation increased in ACA but decreased in AWA, while the opposite pattern occurred during the Medieval Climate Anomaly (MCA). This dipole precipitation pattern is attributed to seasonal differences: increased spring precipitation in ACA together with decreased summer precipitation in AWA shaped the annual precipitation anomaly during the Little Ice Age, with a reversed regime during the Medieval Climate Anomaly. Mechanistically, a negative North Atlantic Oscillation (NAO) phase during LIA springs shifted the westerly moisture transport southward, enhancing moisture supply to ACA and increasing the precipitation there. In contrast, during LIA summers, a positive NAO phase displaced the westerly northward, reducing moisture advection to AWA, while a strengthened Azores High promoted moisture outflow and descending motion, suppressing precipitation. These findings offer a paleo-hydroclimatic basis for anticipating alternating dry-wet regimes between subregions, which can inform adaptive water allocation strategies, drought and flood preparedness, and long-term infrastructure planning across Westerlies Asia in a warming world.

Based on observations, reanalysis data, and numerical experiments, the present study investigates the link between the interannual variation in precipitation over South China (SC) and the eastern Tibetan Plateau (ETP) in July during 1979–2019 and the underlying mechanisms. Results show that during May–September the variation in precipitation exhibits a dipole pattern between the two regions in July and August only, with more significance in July. The correlation coefficients of precipitation between the two regions in July and August are − 0.60 and − 0.34, statistically significant at the 99% and 95% confidence levels, respectively. The role of developing ENSO in the formation of the precipitation dipole in July is further investigated. During El Niño’s development in July, precipitation increases over the tropical central–eastern Pacific, and decreases from India to the Maritime Continent and tropical Atlantic. These conditions cause anomalous cyclones over SC and the northern Bay of Bengal, and an anomalous anticyclone over Lake Balkhash to Northwest China in the middle and lower troposphere via the tropical atmospheric bridge and upper-tropospheric wave trains over Eurasia. This favors the July precipitation dipole with increased (decreased) precipitation over SC (the ETP). In La Niña’s developing phase in July, the opposite is true. Moreover, numerical experiments with the ECHAM5 model can reproduce the above physical processes.

The Tibetan Plateau (TP) precipitation is experiencing the north‐south dipole tendency pattern since 1979. In this study, we identify four primary seasonally evolving patterns (SEPs) that explain approximately 50% of the total variance in precipitation variability over the TP. These SEPs contribute 60%–90% of the spatial mean amplitude of precipitation trends across seasons. In particular, the second SEP that features a north‐south dipole pattern dominates the annual mean trend of the precipitation over the TP. The interdecadal variability of the seasonally evolving north‐south dipole pattern is linked to the interdecadal variations of summer Silk Road Pattern and Indian monsoon. These findings suggest that the climate variability expressed through SEPs could potentially serve as a significant source for the interdecadal rainfall prediction. Plain Language Summary The Tibetan Plateau (TP) is experiencing the north‐wetting‐south‐drying trend due to the imbalance of the Asian water tower since 1979, influencing the water supply to billions of people and regional and global climate. However, the characteristics of the seasonally evolving variations of precipitation across seasons on multiyear timescales, as well as the associated major circulation patterns, remain unknown. Here we identify four primary seasonally evolving patterns (SEPs) and focus on investigating their corresponding long‐term trends and interdecadal variations. These four modes collectively contribute by 60%–90% of the spatial mean amplitude of precipitation trends across seasons. In particular, the trend of the second SEP that features a north‐south dipole explains the spatio‐temporal disparity of the total precipitation trend, displaying the strongest amplitude in summer over the TP. Our findings provide insight into the climate variability manifested in SEPs as a major source for the interdecadal prediction of rainfall evolution in the Asian water tower. Key Points Seasonally evolving patterns (SEPs) explain 60%–90% of the spatial mean amplitude of total precipitation trend over the Tibetan Plateau The second SEP trend with a north‐south dipole pattern mainly contributes to the spatio‐temporal disparity of the total precipitation trend The seasonally evolving north‐south dipole trend is linked to the Silk Road pattern and the Indian monsoon variations

An empirical orthogonal function (EOF) analysis was conducted for spring precipitation gauge data over northeast China (NEC). The first EOF mode is characterized by a homogenous rainfall pattern throughout NEC. The corresponding principal component has both significant interannual and interdecadal variations. This leading mode explains a large portion of the total NEC spring rainfall (NECSR) variances and is statistically independent from other higher modes. The physical processes responsible for the interannual and interdecadal variabilities were investigated via observational diagnoses and numerical experiments. On the interannual time scale, NECSR is mainly affected by the SST anomalies (SSTAs) in the northern tropical Atlantic Ocean. When the SSTAs are positive, the subsequently induced positive precipitation and convection can stimulate two quasi-barotropic Rossby wave trains over the mid- to high latitudes. A cyclonic anomaly center of the Rossby wave train appears over northeastern Asia, leading to a positive rainfall anomaly in the region. On the interdecadal time scale, NECSR is mainly influenced by the SSTAs over the warm-pool region. Positive SSTAs in the warm-pool region result in enhanced convection (ascending motion) around the Maritime Continent and suppressed convection (descending motion) over the central equatorial Pacific Ocean. This zonal dipole convection pattern stimulates a quasi-barotropic circulation pattern with an anticyclonic anomaly over the Tibetan Plateau and a cyclonic anomaly over northeastern Asia. The cyclonic anomaly over northeastern Asia enhances the NECSR. Numerical experiments further suggested that the convective heating anomaly over the Maritime Continent, rather than cooling over the central equatorial Pacific, plays a more essential role in driving the interdecadal rainfall variability of NECSR.

The present study uses observation-based gridded air temperature and precipitation datasets to investigate the spatiotemporal changes in meteorological drought from 1981 to 2020 in South Asia (SA). The drought characteristics i.e., duration, area, frequency, intensity, and severity are calculated using Run theory and the Standardized Precipitation Evapotranspiration Index (SPEI) on annual and seasonal timescales. SA is divided into four homogeneous subregions using the k-means clustering algorithm, while the trends were estimated using Sen’s Slope estimator and modified Mann-Kendall (MMK) test. A state-of-the-art Bayesian Dynamic Linear (BDL) model was employed to assess the sub-regional drought variability and their possible links with large-scale atmospheric drivers such as the Indian Ocean Dipole (IOD), El Niño Southern Oscillation (ENSO), and the Pacific Decadal Oscillation (PDO). It is found that the SA winter season experienced a significant drying long-term trend, especially southwestern and northeastern parts of SA. Drought durations show dipolar patterns with longer drought duration in the southwestern compared to the northern parts of SA. Notably, arid and semi-arid regions have shown significant drying trends in terms of their area, frequency, and severity, implying that meteorological droughts are relatively more severe in those regions. Similarly, the relationship varies over time between drought variability and climate drivers. In particular, the IOD has an impact on drought episodes over southwest SA relative to the northern parts and is mostly affected by the Sea surface temperature (SST) variability. The study results contribute to a better understanding of the meteorological drought characteristics over SA, which is important for disaster risk managers and policymakers to mitigate drought impacts.

Annual precipitation anomalies over eastern China are characterized by a north–south dipole pattern, referred to as the “southern flooding and northern drought” pattern (SF/ND), fluctuating on decadal time scales. Previous research has suggested possible links with oceanic forcing, but the underlying physical mechanisms by which sea surface temperature (SST) variability impacts the dipole pattern remains unclear. Idealized atmospheric general circulation model experiments conducted by the U.S. CLIVAR Drought Working Group are used to investigate the role of historical SST anomalies associated with Pacific El Niño–Southern Oscillation (ENSO)-like and the Atlantic multidecadal oscillation (AMO) patterns in this dipole pattern. The results show that the Pacific SST pattern plays a dominant role in driving the decadal variability of this dipole pattern and the associated atmospheric circulation anomalies, whereas the Atlantic SST pattern contributes to a much lesser degree. The direct atmospheric response to the Pacific SST pattern is a large-scale cyclonic or anticyclonic circulation anomaly in the lower troposphere occupying the entire northern North Pacific. During the warm phase of the Pacific SST pattern, it is cyclonic with northwesterly wind anomalies over northern China pushing the monsoon front to the south and consequently SF/ND. During the cold phase of the Pacific SST pattern, the circulation anomaly reverses with southeasterly winds over northern China allowing the monsoon front and the associated rainband to migrate northward, resulting in southern drought and northern flooding. The Atlantic SST pattern plays a supplementary role, enhancing the dipole pattern when the Pacific SST and Atlantic SST patterns are in opposite phases and weakening it when the phases are the same.

The large-scale circulation associated with extreme precipitation over the middle reaches of Yangtze river (MRYR) in early summer (June and July) are classified into three canonical patterns via hierarchical clustering. The clustering results reveal a clear connection between the MRYR extreme precipitation and anomalous moisture convergence over this region with the eastward expansion of South Asia High and intensified westerly jets providing additional forcing for local rising motion. In all three clusters, the anomalous moisture convergence results from anomalous low-level southwesterlies encountering anomalous northerlies from mid-high latitudes. The southwesterly anomaly is associated with the expansion of the Western Pacific Subtropical High (WPSH). However, the anomalous northerlies weakening the northward advance of the Mei-yu front are mainly driven by different extratropical circulation anomalies in the three clusters. These anomalies range from zonally-elongated barotropic disturbances to developing baroclinic disturbances that are potentially tied to upstream storm tracks. All three clusters are characterized by a meridional dipole in geopotential height anomaly over the tropical–subtropical East Asia. The northern and also more pronounced node of the dipole is located over the MRYR with a cyclonic (anti-cyclonic) height anomaly in the lower (upper) troposphere, suggesting the critical role played by anomalous latent heating of extreme MRYR rainfall in driving the formation of this dipole. This dipole anomaly projects effectively onto the negative phase of the Pacific–Japan teleconnection pattern and acts partly as a positive feedback to the westward expansion of the WPSH. Also discussed are the implications of the identified large-scale circulation patterns for model evaluation and operational forecasting of extreme precipitation events.

In recent decades, an increasing persistence of atmospheric circulation patterns has been observed. In the course of the associated long-lasting anticyclonic summer circulations, heatwaves and drought spells often coincide, leading to so-called hotter droughts. Previous hotter droughts caused a decrease in agricultural yields and an increase in tree mortality. Thus, they had a remarkable effect on carbon budgets and negative economic impacts. Consequently, a quantification of ecosystem responses to hotter droughts and a better understanding of the underlying mechanisms are crucial. In this context, the European hotter drought of the year 2018 may be considered a key event. As a first step towards the quantification of its causes and consequences, we here assess anomalies of atmospheric circulation patterns, maximum temperature, and climatic water balance as potential drivers of ecosystem responses which are quantified by remote sensing using the MODIS vegetation indices (VIs) normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). To place the drought of 2018 within a climatological context, we compare its climatic features and remotely sensed ecosystem response with the extreme hot drought of 2003. The year 2018 was characterized by a climatic dipole, featuring extremely hot and dry weather conditions north of the Alps but comparably cool and moist conditions across large parts of the Mediterranean. Analysing the ecosystem response of five dominant land cover classes, we found significant positive effects of climatic water balance on ecosystem VI response. Negative drought impacts appeared to affect an area 1.5 times larger and to be significantly stronger in July 2018 compared to August 2003, i.e. at the respective peak of drought. Moreover, we found a significantly higher sensitivity of pastures and arable land to climatic water balance compared to forests in both years. We explain the stronger coupling and higher sensitivity of ecosystem response in 2018 by the prevailing climatic dipole: while the generally water-limited ecosystems of the Mediterranean experienced above-average climatic water balance, the less drought-adapted ecosystems of central and northern Europe experienced a record hot drought. In conclusion, this study quantifies the drought of 2018 as a yet unprecedented event, outlines hotspots of drought-impacted areas in 2018 which should be given particular attention in follow-up studies, and provides valuable insights into the heterogeneous responses of the dominant European ecosystems to hotter drought.

Tibetan Plateau (TP) precipitation is affected by anomalous circulation systems in both the tropics and mid-latitudes, due to the TP’s unique geographical location. By using observational, reanalysis, and CMIP6 model datasets, this study reveals the individual and joint effects of the Indian Ocean Dipole (IOD) and Silk Road pattern (SRP) on the interannual variability of TP precipitation in September. In the positive IOD phase, the zonal gradient of the sea-surface temperature anomalies (SSTAs) drives a Gill-type response with an anticyclonic anomaly over the Indian subcontinent and Bay of Bengal. To the north, anomalous westerlies induce a shallow trough, and the associated anomalous southwesterlies transport moisture to the southeastern TP, resulting in surplus precipitation there. Meanwhile, the westerly jet disturbances over the North Atlantic excite an SRP-like pattern, resulting in a baroclinic structure in northern India with the upper (lower) tropospheric anomalous anticyclone (cyclone) over west-central Asia (northern India). The anomalous southwesterlies to the east of the low-level cyclone transport abundant moisture to the southeastern TP, which results in increased precipitation there. The joint effects of IOD and SRP can explain nearly 52% of the TP precipitation anomaly, exceeding the contribution of IOD (19%) and SRP (27%) alone. Our results highlight the necessity of considering the joint effects of drivers in the tropics and mid-latitudes, providing a basis for more accurate simulations and predictions of TP precipitation.