Impact of Tibetan Plateau Spring Snow on the Summer Heat Wave Frequency Over the Indochina Peninsula

摘要

In this work, we investigated the impact of the interannual variation in Tibetan Plateau snow cover (TPSC) on the summer heat wave frequency (HWF) over the Indochina Peninsula (ICP) (HWF_ICP) for 1981-2020. This study shows that the spring TPSC variation over the central Tibetan Plateau (TP) is positively correlated with the summer HWF_ICP and can explain up to 30 of the summer HWF_ICP variance. Analysis of the apparent heat source shows that more-than-normal spring snow cover over the central TP has a cooling effect on the above atmosphere, which induces negative geopotential height anomalies in the upper troposphere. The anomalous spring TPSC and its cooling effect can persist until summer. In summer, the TPSC-associated low anomalies propagate eastward to the East Asia-Japan Sea area. The anomalous westerly winds along the south flank of these low anomalies strengthen the climatological westerly jet. Changes in the westerlies are accompanied by anomalous ascending and descending air motion north and south of 30 DEG;N over the coast of East Asia and the western Pacific. The anomalous descending air motion south of 30 DEG;N causes an enhanced subtropical high, less cloud cover, and more downward solar radiation, which are favorable conditions for a greater occurrence of heat waves over the ICP. The results of current study may provide useful information for improving the seasonal forecast skill of the summer HWF_ICP variation.