Understanding the Mechanisms of Summer Extreme Precipitation Events in Xinjiang of Arid Northwest China

As one of the aridest regions in the mid-latitudes, arid Northwest China (ANC) has scarce water resources year-round, its annual total precipitation is mainly contributed by summer extreme precipitation events, which may also cause disastrous flash floods. However, the physical mechanism and climatic features of extreme precipitation events in ANC are not fully understood and warrant in-depth investigations. Taking Xinjiang as an example, this study investigates the underlying mechanisms and long-term trend of extreme precipitation events in ANC during 1961-2019 using observational and reanalysis data sets. Results suggest that summer extreme precipitation events in ANC are characterized by a zonal wave pattern with the deepening of the western Siberian trough, central Asian high, and Mongolian high. Under the effects of the zonal wave pattern, the westerly and the easterly airflows anomalously intensify and converge in ANC, transporting a large amount of water vapor from the Arctic Ocean, the Caspian Sea, the Aral Sea, the Arabian Sea, and eastern China to ANC. Meanwhile, a deep anomalous cyclone center induced by the deep wave pattern appears over ANC, thus providing favorable conditions for the occurrence of extreme precipitation events in ANC. Over the long-term period, total summer precipitation and the frequency of extreme precipitation events in ANC show significant increasing trends, indicating that summer climate in ANC is becoming more humid, and extreme precipitation events are becoming more frequent. These findings provide scientific insights for understanding the formation mechanism of summer extreme precipitation events and mitigating the corresponding disasters in arid regions.

Automated summary

The study reveals that extreme precipitation events in arid Northwest China display a specific zonal wave pattern with the deepening of the western Siberian trough, central Asian high, and Mongolian high. Long-term observations show a significant increasing trend in both total summer precipitation and the frequency of extreme precipitation events, indicating a more humid climate and more frequent extreme precipitation events in the region.