Cause analysis of a southwesterly airflow warm-sector heavy rainfall event in Henan

Based on meteorological observation,radar data,satellite data and NCEP 1°×1° reanalysis data every 6h,using the methods of synoptic analysis and physical quantity diagnosis,the occurrence and development mechanism of southwesterly airflow warm-sector heavy rainstorm in the Huanghuai region of Henan Province in July 2017 was analyzed.The results show that the mainly influence system of the heavy rainfall is the low and medium level jet.The unstable energy comes from the dry and cold upper layer with the warm and wet lower layer.The water vapor convergence and transport is mainly located near and below 850 hPa or 925 hPa.The strong water vapor convergence between the low level and near-surface,and the surface mesoscale convergence line are important triggering mechanisms for warm-sector heavy rainfall.The obviously dynamic frontogenesis provides a strong upward movement for heavy rainfall.The coupling of high and low level jet is the mainly dynamic strengthening mechanism.The heavy rainfall occurred in the gradient area of the high and low centers of TBB or near the center of lower TBB values,and the area of TBB lower than 220 K have an important indication significance for the heavy rainstorm area above 100 mm; The echo of heavy precipitation presents the characteristics of backward propagation and quasi-stationary,and the echo has warm cloud echo precipitation structure with low centroid meanwhile.