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El Niño is a dominant source of interannual climate variability around the world. Based on the observed and reanalyzed datasets for the period of 1958–2019, this study explores the influence of El Niño on the spring precipitation over the Indochina Peninsula (ICP). The results show that El Niño has a significant negative correlation with the following spring precipitation over the ICP. However, this climatic teleconnection of El Niño was unstable, with an obvious interdecadal strengthening since the early 1990s. During the decaying spring, the El Niño–related sea surface temperature (SST) anomalies would induce an abnormal downward motion along with an anomalous low-level anticyclone over the western North Pacific. Before the early 1990s, such El Niño–induced atmospheric circulation anomalies were located to the east of the ICP, exerting little influence on the spring ICP precipitation. In contrast, since the early 1990s, the abnormal downward motion and anomalous low-level anticyclone extended westward covering the whole ICP, hampering local spring precipitation. This interdecadal change is owing to a relatively stronger intensity and longer duration of the El Niño–related warm SST anomalies over the tropical central Pacific in the epoch after the early 1990s (1992–2019) than in the previous decades (1958–91). Our findings highlight a strengthening effect of El Niño on the following spring climate over the ICP since the early 1990s, which has great implications for the regional climate prediction. Significance Statement: Spring precipitation variation has profound economic and societal influences for the Indochina Peninsula (ICP) that consists of several agriculture-based countries. Moreover, the local soil moisture anomaly induced by the ICP spring precipitation is an important seasonal predictor for the East Asian summer monsoon and extreme climate. Here this study identifies a strengthening influence of El Niño on the following spring precipitation over the ICP, due to a relatively stronger intensity and longer duration of the El Niño–related warm SST anomalies over the tropical central Pacific since the early 1990s. This may provide an important implication for the seasonal predictions of summer monsoon and extreme climate over East Asia and thus potentially enhance the predictability of regional climate. [ABSTRACT FROM AUTHOR]

An integrated picture of the future changes in the water cycle is provided focusing on the global land monsoon (GLM) region, based on multimodel projections under the representative concentration pathway 8.5 (RCP8.5) from phase 5 of the Coupled Model Intercomparison Project (CMIP5). We investigate the reservoirs (e.g., precipitable water, soil moisture) and water fluxes (e.g., precipitation P, evaporation E, precipitation minus evaporation P − E, and total runoff) of the water cycle. The projected intensification of the water cycle with global warming in the GLM region is reflected in robust increases in annual-mean P (multimodel median response of 0.81% K−1), E (0.57% K−1), P − E (1.58% K−1), and total runoff (2.08% K−1). Both surface (−0.83% K−1) and total soil moisture (−0.26% K−1) decrease as a result of increasing evaporative demand. Regionally, the Northern Hemispheric (NH) African, South Asian, and East Asian monsoon regions would experience an intensified water cycle, as measured by the coherent increases in P, P − E, and runoff, while the NH American monsoon region would experience a weakened water cycle. Changes in the monthly fields are more remarkable and robust than in the annual mean. An enhanced annual cycle (by ~3%–5% K−1) with a phase delay from the current climate in P, P − E, and runoff is projected, featuring an intensified water cycle in the wet season while little changes or slight weakening in the dry season. The increased seasonality and drier soils throughout the year imply increasing flood and drought risks and agricultural yields reduction. Limiting global warming to 1.5°C, the low warming target set by the Paris Agreement, could robustly reduce additional hydrological risks from increased seasonality as compared to higher warming thresholds. [ABSTRACT FROM AUTHOR]

Numerous studies have been conducted on the impact of soil moisture on the climate, but few studies have attempted to diagnose the linkage between soil moisture and climate variability using observational data. Here, using both observed and reanalysis data, the spring (April--May) soil moisture is found to have a significant impact on the summer (June--August) monsoon circulation over East Asia and precipitation in east China by changing surface thermal conditions. In particular, the spring soil moisture over a vast region from the lower and middle reaches of the Yangtze River valley to north China (the YRNC region) is significantly correlated to the summer precipitation in east China. When the YRNC region has a wetter soil in spring, northeast China and the lower and middle reaches of the Yangtze River valley would have abnormally higher precipitation in summer, while the region south of the Yangtze River valley would have abnormally lower precipitation. An analysis of the physical processes linking the spring soil moisture to the summer precipitation indicates that the soil moisture anomaly across the YRNC region has a major impact on the surface energy balance. Abnormally wet soil would increase surface evaporation and hence decrease surface air temperature ( Ta). The reduced Ta in late spring would narrow the land--sea temperature difference, resulting in the weakened East Asian monsoon in an abnormally strengthened western Pacific subtropical high that is also located farther south than its normal position. This would then enhance precipitation in the Yangtze River valley. Conversely, the abnormally weakened East Asian summer monsoon allows the western Pacific subtropical high to wander to south of the Yangtze River Valley, resulting in an abnormally reduced precipitation in the southern part of the country in east China. [ABSTRACT FROM AUTHOR]