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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]

The central China summer precipitation (CCSP) is of great importance to the people's livelihood of this densely populated region, including the agriculture, ecosystems, water resources, economies, and health. Based on the observed precipitation, sea surface temperature (SST), and atmospheric reanalysis datasets, the present study investigates the effects of El Niño in the developing stage on the CCSP during 1960–2014. The results show that the CCSP anomalies exhibit significant negative correlations with the El Niño-related SST anomalies in both the simultaneous summer and the following winter, implying that the developing El Niño is important for modulating the CCSP. However, this climatic teleconnection of El Niño is unstable, with an obvious interdecadal change around the late 1980s. Specifically, the negative correlation is not statistically significant in the previous epoch before the late 1980s (1960–1988), but dramatically strengthens since the late 1980s (the post epoch for 1989–2014). Such an interdecadal change is closely associated with the change of the El Niño-related SST anomaly pattern. Compared to the previous epoch, the central Pacific El Niño occurs more frequently in the post epoch, leading to an interdecadal shift of the maximum warm SST anomalies from the eastern Pacific to the central Pacific. The resultant westward extension of the atmospheric circulation responses induces an anomalous low-level cyclone covering South China in the post epoch. It would prevent the southwest monsoon from delivering the moisture to the north and hence reduce the CCSP. While, in the previous epoch, the anomalous cyclone locates east of South China, exerting insignificant influence on the CCSP. This work highlights a strengthening effect of El Niño on the CCSP since the late 1980s, with great implications for the regional seasonal climate prediction. [ABSTRACT FROM AUTHOR]

Previous studies suggested that the dry–wet surface state over the Indo-China Peninsula (ICP), closely associated with the local spring precipitation, is an important seasonal predictor for the East Asian summer monsoon and extreme climate. Hence, this work investigates the inter-annual variability of spring precipitation over the ICP and its relationship with El Niño-Southern Oscillation (ENSO) during 1958–2019. The results show that the spring precipitation anomalies over the ICP are highly linked to the ENSO-induced atmospheric circulation anomalies. In particular, there are large asymmetries in the precipitation anomalies for the spring following ENSO. During the decaying spring of the El Niño events, the precipitation decrease mainly occurs over the Western ICP associated with an anomalous low-level anticyclone over the western North Pacific. In contrast, during the decaying spring of the La Niña events, a stronger precipitation increase broadly extends into the Southeastern ICP. This is owing to a nonlinear effect of ENSO on the atmospheric circulation. Compared to El Niño, the abnormal center of La Niña extends too far westwards, inducing a westward movement of the anomalous atmospheric circulation, which results in a stronger effect on the spring ICP precipitation. Our findings emphasize the nonlinear responses of the spring ICP precipitation to ENSO. This has important implications for the seasonal climate prediction over the ICP, especially for the Southeastern ICP countries/regions. [ABSTRACT FROM AUTHOR]

The Yangtze region of South East China has experienced several extreme hot summer months in recent years. Such events can have devastating socio-economic impacts. We use a large ensemble of initialised climate simulations to assess the current chance of unprecedented hot summer months in the Yangtze River region. We find a 10% chance of an unprecedented hot summer month each year. Our simulations suggest that monthly mean temperatures up to 3 °C hotter than the current record are possible. The dynamics of these unprecedented extremes highlights the occurrence of a stationary atmospheric wave, the Silk Road Pattern, in a significant number of extreme hot events. We present evidence that this atmospheric wave is driven by variability in the Indian summer monsoon. Other extreme events are associated with a westward shift in the western North Pacific subtropical high. The most extreme simulated events exhibit combined characteristics of both the Silk Road Pattern and the shifted western North Pacific subtropical high. [ABSTRACT FROM AUTHOR]

During 2016 boreal summer and fall, a strong negative Indian Ocean Dipole (IOD) event occurred, which led to large climate impacts such as the drought over East Africa. In this study, efforts are made to understand the dynamics of this IOD event and to evaluate real-time IOD predictions from current operational seasonal forecast systems. We show that both the wind-evaporation-SST and thermocline feedback lead to fast IOD growth in boreal summer 2016. Anomalous westerlies over the tropical Indian Ocean warmed the sea surface temperature (SST) over the tropical southeastern Indian Ocean (TSEIO) by reducing local evaporation; and wind induced thermocline deepening increased TSEIO SST by vertical advection. The intraseasonal disturbances in May induced the early subsurface warming and initiated the 2016 IOD. Due to negative cloud-radiation-SST feedback, the 2016 IOD event decayed quickly after October. We also demonstrate the successful real-time IOD predictions by the operational Hadley Center Global seasonal forecasting system version 5 (GloSea5) and the Beijing Climate Center Climate System Model (BCC-CSM1.1m). Resulting from the realistic representation of observed air-sea interactions, both models successfully predicted the evolution of the 2016 IOD up to 2 seasons ahead. The skillful prediction is also due to the precursor of the early subsurface warming in the eastern Indian Ocean, which increases intrinsic predictability of the 2016 IOD event. It is also demonstrated that IOD amplitude biases can be reduced by the joint-model prediction. The successful prediction of the 2016 IOD event allowed the East African drought to be predicted 4-6 months ahead. Our study reveals that current operational climate models can give useful warning of impending IOD events and impending climate extremes. [ABSTRACT FROM AUTHOR]

The Yangtze River Valley (YRV) experienced an unprecedented heatwave in midsummer of 2022. Still, the detailed physical processes involved in the influence of abnormal large-scale atmospheric circulation on the heatwave remain unexplored. Here, we show that the positive meridional gradient of anomalous atmospheric moisture at the middle-lower troposphere and associated extreme dry air advection over the YRV are vital prerequisites for forming the 2022 YRV heatwave. The 2022 YRV heatwave is dominated by interannual variability, contributing 72.7% to the total temperature anomalies. Diagnosis of the surface heat budget equation indicates that the surface cloud radiative forcing is the most critical process in driving the 2022 YRV heatwave, which is dominated by the positive surface short-wave cloud radiative forcing associated with the suppressed precipitation and the middle-low clouds. The suppressed precipitation is induced by the vertical dynamical processes of anomalous moisture advection caused by the abnormal descending flows over the YRV, which are driven by the negative advection of anomalous latent heat energy by climatological meridional wind (anomalous dry air advection) according to the atmospheric moist static energy equation. Simulations from the Lagrangian model FLEXPART further indicate that the moisture anomaly over the north of YRV mainly originated from the surface evaporation in the YRV, implying that there is a positive land-air feedback during the life cycle of the YRV heatwave. Our study enriches the mechanism understanding of the 2022 YRV heatwave from the perspective of surface energy budget and land-air feedback. [ABSTRACT FROM AUTHOR]