Distinct Holocene precipitation trends over arid Central Asia and linkages to westerlies and Asian monsoon

Abstract

Abstract The response of precipitation over arid Central Asia since the mid Holocene is long considered to be controlled by astronomical insolation-induced changes in the westerlies. However, it is still controversial in proxy and modeling studies whether the trend of Central Asian precipitation is in accordance with Asian monsoon or not. Compared to the monsoon, the westerlies-associated precipitation changes are complicated and also rely on regional mountain complex. In this study, we conducted a high-resolution transient experiment by a coupled climate model to evaluate the response of Central Asian precipitation. The simulated precipitation changes are distinctly different over regions although they are mainly associated with the westerlies. Since mid Holocene, the annual precipitation increases over Balkhash-Altai region but decreases over Turan Plain, Mongolia-Baikal and Tarim Basin, in all of which the summer precipitation contributes most. Following the summer insolation, the southward shift of westerly jet is accompanied by wave-like anomalies in the upper-tropospheric meridional winds across mid-latitude Eurasia (the Silk Road pattern), which results in distinct summer precipitation changes. The decreased precipitation over Tarim is mainly explained by weakened low-level easterly wind anomaly and less moisture supply from East Asia. In contrast, the responses of winter precipitation are limited even in the winter-rainfall-dominated regime due to the small insolation change. Such simulated complicated precipitation trends during the Holocene are in qualitative agreement with existing proxies, highlighting the modulation of Silk Road pattern on Central Asian rainfall on the orbital timescale.