Increasing summer precipitation in arid Central Asia linked to the weakening of the East Asian summer monsoon in the recent decades

Abstract

It is generally believed that water vapour from the North Atlantic transported by the mid‐latitude westerlies dominates precipitation variations in arid Central Asia, where monsoonal water vapour source is beyond the reach. This study reexamines water vapour sources for arid Central Asia based on daily reanalysis data. The results reveal two water vapour sources for arid Central Asia: the westerly water vapour transport from the North Atlantic and the monsoonal water vapour transport from the tropical Indian Ocean and South China Sea. The monsoonal transport includes two pathways: lower tropospheric water vapour along the eastern and northern periphery of the Tibetan Plateau from the tropical Indian Ocean and South China Sea, and middle‐upper tropospheric water vapour via the Tibetan Plateau from the tropical Indian Ocean. Precipitation variability during the monsoonal transport events explains 81% of the total variance. The monsoonal transport is related to a weakened East Asian summer monsoon (EASM) that is accompanied by persistent westward shift of the western Pacific subtropical high and increasing frequency of Mongolian anticyclone activities. The EASM has experienced a persistent weakening trend since 1958, causing an increasing contribution of the monsoonal water vapour transport and thereby enhancing summer precipitation in arid Central Asia. In particular, the monsoonal easterly water vapour has become the dominant source for arid Central Asia in the lower troposphere during the last decade. This study highlights the important role of the EASM in the wetting trend of summers in arid Central Asia during the past six decades.

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

“…The thermodynamic component of the moisture convergence is induced by the increased specific humidity associated with enhanced evaporation (Peng & Zhou, 2017; Trenberth, 2005; Wu et al., 2019), while its dynamic component is dominated by an anomalous cyclone over central Asia that is associated with a significant southward displacement of the Asian subtropical westerly jet (Peng & Zhou, 2017). Additionally, the increasing precipitation (and extreme precipitation) in ANC may also be closely related to the weakened East Asian summer monsoon that promotes the westward transport of water vapor from the Indian and Pacific Oceans to ANC by intensifying the westward extension of the western Pacific subtropical high and increasing Mongolian anticyclonic activities (C. Chen et al., 2020; F. Chen et al., 2021). It is noted that the rationale for putting the synoptic diagnostics and wetting trends together in ANC is still not fully understood and warrant in‐depth investigations.…”

The Influence of the Tibetan Plateau Monsoon on Summer Precipitation in Central Asia

“…The change in westerly circulation may be the main factor affecting the evolution of precipitation in the arid region of Central Asia (Chen et al, 2011). Chen et al (2021) also found that the East Asian summer monsoon has experienced a persistent weakening trend since 1958, causing an increasing contribution of monsoonal water vapor transport and enhancing summer precipitation in Central Asia. Besides these factors, Peng et al (2018) also found that human-induced warming increased the specific humidity over all of Central Asia, increasing (decreasing) the precipitation over eastern (western) Central Asia.…”

Hydrological Evolution of a Lake Recharged by Groundwater in the Badain Jaran Desert Over the Past 140 years

“…Research integrating ice cores, stalagmites, and lake records reveals that the temperature of Northwest China warmed rapidly at the beginning of the 1950s (Figure 6D; Ding, 2010), which is consistent with the rapid warming trend in China (Ge et al, 2015). With rising temperatures, precipitation in the arid region of Northwest China has increased in recent decades (Chen et al, 2020;Liu et al, 2021). The reconstructed precipitation from tree rings shows that the annual precipitation began to increase at the beginning of the 1950s on the southern margin of the desert and the northeastern Tibetan Plateau (Figure 6C; Yang et al, 2010;Yang et al, 2014;Zhang et al, 2015;Liu et al, 2021).…”