Multi-scale comparative analysis of two torrential rain events in Tianjin on the edge of the SubtropicalHigh

Abstract：Based on conventional meteorological data, intensive AWS data, NCEP 1°×1 ° reanalysis data, satellite brightness temperaturedata, Doppler radar data, VDRAS data and wind profiler data, two torrential rain events in July 2012 were analyzed. The results showed that:(1) as to the causes of the precipitation, the“7·21”event belonged to a“frontal precipitation”, which had more favorable dynamic conditions,while the“7·25”event belonged to a“warm area precipitation”, which had statically more unstable conditions. (2) The southeast airflow atthe top of typhoon“Vicent”, and the southerly airflow at the edge of subtropical high constitute water vapor channels for the two heavy rainevents in North China, although their convergence areas were different. (3) After cold air intrusion, the convective system of the“7·21”eventwas more well-organized, while the“7·25”event was triggered by the convergence in southerly flow. The maintaining mechanism of the twotorrential rain events were both related to the convergence of thunderstorm outflow and the southerly flow. The MCS in the ”7·21”eventmoved from northwest to southeast, as the trough line moving to the east, but the MCS in the“7·25”events moved from southwest to northeast,which was forced by southwesterly flow.