Evolution of the Circulation Anomalies and the Quasi-Biweekly Oscillations Associated with Extreme Heat Events in Southern China

摘要

Southern China, located in the tropical-subtropical East Asian monsoonal region, presents a unique anticyclonic-cyclonic circulation pattern during extreme heat (EH), obviously different from the typical anticyclone responsible for EH in many other regions. Associated with the evolution of EH in southern China, the anticyclonic-cyclonic anomalies propagate northwestward over the Philippines and southern China. Before the EH onsets, the anticyclonic anomaly dominates southern China, resulting in stronger subsidence over southern China and stronger southerly (southwesterly) flow over the western (northern) margins of southern China. The southerly (southwesterly) flow transports more water vapor to the north of southern China, thus, together with the local stronger subsidence, resulting in drier air condition and accordingly favoring the occurrence of EH. Conversely, after the EH onsets, the cyclonic component approaches southern China and offsets the high temperature.