Analysis of the Physical Field for Two Types of Southwest Vortexes before Formation Period in Sichuan-Chongqing Region

Based on the ground automatic station routine data,sounding data and NCEP reanalysis data,25 southwest vortexes with rainstorm and 25 ones with non-rainstorm happened in the area (27 ~ 33°N,105 ~ 110°E) are selected from 2009 to 2012. Significant differences are found between the environment physical quantities of the two types of southwest vortexes with rainstorm and non-rainstorm about 6h prior to formation by using the reanalysis data for comparative analysis of the reanalysis data: In the low troposphere,intensity and scale of the southwest vortexes with rainstorm comparison with non-rainstorm are stronger and larger,also stronger exhibition in the mixing of cold and warm air and cold air intruding into its northwest edge. In the middle troposphere,there exists small trough in upstream of the vortexes with rainstorm comparison non-storm. In the upper troposphere,the center formation of vortexes with rainstorm are located in the northeast of the South Asia high,the upper level jet appeared at about 500 km north of vortex. The center formation of vortexes with non-storm are located in the upper level jet and absent the closed South Asia high. For the southwest vortexes with rainstorm,relative to the one with non-rainstorm,the water vapor of transportation and convergence is large. The characteristic of consistency of superimposition of the positive vorticity and convergence in low level corresponding with the negative vorticity and divergence in upper level is more obvious for the southwest vortexes with rainstorm,which is less significant for the southwest vortexes with non-rainstorm. The center of the southwest vortexes with rainstorm and nearby exists the max value center of the upward movement,and the west,south and center of the vortexes is the instability or neutral stratification atmosphere. The center of the neutral stratification atmosphere in low level of the southwest vortexes with non-rainstorm isn't the max value center of the upward movement.