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

Abstract

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.

Changes in temperature and precipitation extremes in the arid regions of China during 1960–2016

“…Based on these findings, we conclude that the total amount of precipitation, as well as the intensity and frequency of extreme precipitation events, have increased in China's arid regions since 1960. Ning et al (2021) also confirmed these Regionally averaged series for the extreme precipitation indices in the arid regions of China from 1960 to 2016. The indices are defined in Table 1.…”

An Observational Investigation of Spatiotemporally Contiguous Heatwaves in China From a 3D Perspective

“…It has been suggested that heatwaves in northwestern China are often accompanied by the westward movement of anomalously atmospheric blocking associated with the progression of Rossby waves in the upper‐level troposphere (Luo et al., 2020; Pfahl & Wernli, 2012). The eastward propagation of the mid‐latitude Rossby wave trains from the west (e.g., the North Atlantic) has also been suggested to contribute to summer extreme precipitation events in the Eurasian continent (Ning et al., 2021; Saeed et al., 2014). In contrast, heatwaves in southeastern China are mainly triggered by the westward movement and extension of the western North Pacific subtropical high (WNPSH) (Ding et al., 2010; Luo & Lau, 2017).…”

Spatiotemporal Evolution Patterns of Contiguous Extreme Precipitation Events Across China From a 3D Perspective

“…The SCEPEs moving from Northwest China to North–Northeast China are likely related to the eastward propagation of the Rossby waves (i.e., the Silk‐Road wave‐train) in the upper atmospheres over the mid‐latitudes (Ning et al., 2021; Zhang et al., 2020). These Rossby waves drive the low‐pressure systems moving eastward along with the westerlies of the East Asian jet stream, resulting in the sequential precipitation processes that occur in Northwest, North, and Northeast China in turn (Orsolini et al., 2015).…”