Seasonal changes in East Asian monsoon-westerly circulation modulated by the snow-darkening effect of mineral dust

The snow-darkening forcing of dust (SFD) is known to occur when dust-covered snow reduces surface albedo and absorbs more radiation, which causes snowmelt and surface warming. To date, few studies have focused on how SFD affects atmospheric circulation. In this study, we used a climate model to evaluate the influence of the SFD on seasonal changes in coupled monsoon westerlies over East Asia. The results indicate that the SFD causes anomalies in temperature, precipitation, and atmospheric circulation over East Asia. In December and January (DJ), the temperature increase over the Tibetan Plateau is significant, and the anomalous anticyclonic circulation causes a weakening of the westerly circulation during this period. In February, March, and April (FMA), the SFD causes an increase in temperature over the plateau and its eastern flank and widespread anomalous cooling to the north, which can be attributed to diabatic cooling of the upper atmosphere. These changes in thermal conditions lead to enhanced westerly winds and weakened East Asian winter monsoons during FMA. The enhanced westerly winds bring more precipitation to the East Asian continent. In May, June, and July (MJJ), only the Tibetan Plateau is significantly warmed in East Asia. At this time, the westerly circulation weakens, and the East Asian summer monsoon strengthens. The low-level atmospheric circulation shows anomalous westerly winds over South Asia. The anomalous westerly winds from Central Asia bring dry air and result in reduced precipitation over India.