Analysis on Gravity Waves and Moist Potential Vorticity During a Rainstorm Process

Based on the NCEP daily reanalysis data and the conventional surface observations in the middle and eastern part of Sichuan Province,an analysis of gravity waves and wet vorticity during the rainstorm on July 31,2009 was carried out.As the motion in the atmosphere without diabatic heating and frictional dissipation conserves moist potential vorticity,it is showed that the moist potential vorticity distribution and temporal change was closely related to the development of the heavy rainfall.The divergence fields and diagnostic results of the non-linear balance equation showed that the gravity wave characteristics had a very significant change during heavy rainfall.The atmospheric instability not only is the excitation source of heavy rain,but also generates gravity waves,so moist potential vorticity and gravity waves play a good role in the forecast of the heavy rainfall.