Analysis of the Mesoscale Characteristics of a Rainstorm Process

Based on conventional observations,rainfall observations from automatic weather stations,satellite cloud images and radar data,a rainstorm process occurred during August 15-18,2011 in Longnan of Gansu Province was analyzed.The results show that a large amount of energy was accumulated from the previous high temperature,the formation and continuance of the southwestern vortex and the plateau vortex,the southwest warm and wet airflow over the Subtropical high periphery,and cold air moving southward resulted in this rainstorm weather process.The instability stratified atmosphere triggered by the cold air,and the pumping effect of the divergence on upper level and convergence on lower level made water vapor rise and coagulate in succession,which resulted in development and continuance of the heavy rain.In addition,the β mesoscale convective cloud strengthened because of terrain and underlying surface,and the heavy rainfall area was mainly at the edge of the β mesoscale convective cloud.Heavy rainfall was similar basically with the strong radar echo centre in the radar echo section,and the train effect of the radar echo resulted in rainstorm.