Interdecadal Variability of Summer Extreme Precipitation in Eastern Northwest China and Its Relationship With Sea Surface Temperature Anomalies in the North Atlantic and Indian Oceans

Abstract

Extreme precipitation events in eastern Northwest China, which can have considerable socioeconomic and societal impacts, have become increasingly frequent in association with climate change. This study found clear interdecadal variability in summer extreme precipitation over eastern Northwest China during 1961–2022, and investigated related variations in atmospheric circulation and sea surface temperature (SST) anomalies. Results indicated that SST changes in the North Atlantic and the Indian Ocean play a key role in the occurrence of extreme precipitation in eastern Northwest China on the interdecadal time scale. When the Indian Ocean Basin‐like mode is in its positive phase, the easterly winds driven by this anomalous anticyclone strengthen the subtropical high and enhance water vapour transport to the Central South Peninsula. Meanwhile, the westerly flow associated with the anticyclonic circulation over South Asia also transports water vapour to both the Central South Peninsula and the South China Sea. The water vapour is then carried to eastern Northwest China by the southerly winds on the western flank of the subtropical high over China, providing the moisture conditions essential for extreme precipitation. In the negative phase of the Atlantic Multidecadal Oscillation, a positive‐phase circumglobal teleconnection wave exists in the upper levels of the troposphere, and a centre of anomalous low pressure over eastern Northwest China, within the western part of this wave train, is linked to a centre of anomalous high pressure over East Asia. This pattern facilitates divergence of the upper‐level airflow, causing ascent and convergence of cold and warm air masses, thereby influencing the interdecadal variation of summer extreme precipitation in eastern Northwest China. The findings of this study enhance understanding of the interdecadal variation of summer extreme precipitation in eastern Northwest China, and provide a scientific basis for improved precipitation forecasting and disaster risk reduction in the region.

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