Wind Field Characteristics of Heavy Precipitation Process in Western Sichuan Basin Based on Wind Profiler Radar Data
According to the classification of warm-sector rainstorm(the southwest vortex,the edge of subtropi-cal high,the southwest jet,and the southeast wind types),four rainstorm processes are selected under the differ-ent weather background in the west of Sichuan Basin(Chengdu area).The wind profile characteristics of heavy precipitation in the initial and developmental stages are analyzed by using the new wind profiler radar data in dif-ferent types of warm-sector rainstorms.The main results are as follows:(1)Wind profiler radar data can clearly show the meso-scale systems that exists in the troposphere and boundary layer.The evolution characteristics of wind field in different types of heavy precipitation are closely related to the interaction of the unique terrain of the Qinghai-Xizang Plateau and the Sichuan Basin with the regional circulation and weather system.Except for the edge of subtropical high warm-sector rainstorm,the northeast wind or easterly wind appeared before or during the typical process of the other three warm-sector rainstorms.(2)A large gradient of vertical velocity intuitively reflects the characteristics of short time and strong convection in these processes.There is a sudden change of ver-tical velocity at the beginning of heavy precipitation,that the downward vertical velocity is apparently weakened or even turned to the upward,which means the upward motion in the atmosphere is significantly enhanced.This abrupt change in vertical velocity has indicative significance for the prediction of heavy precipitation.(3)The ex-tremum of vertical velocity will increase significantly before or during the heavy precipitation,accompanied by the decrease of the extreme layer height,due to the fall of precipitation particles.During the southwest vortex rainstorm,the change of the extremum of vertical velocity was basically ahead of the change of precipitation in-tensity by half hour to 1 hour.The extremum of horizontal wind speed and the extreme layer height change syn-chronously.Before the most of heavy precipitation processes,the meso-scale jet appeared in the mesosphere,ac-companied by the decrease of the jet layer.(4)Low-level jet is involved in all four types of warm-sector rain-storm.In the process of the edge of subtropical high and the southwest vortex rainstorm,the precipitation could be predicted after 1 hour to 2 hours by the first increase of low-level jet index.The low-level jet could provide wa-ter vapor and turbulence during heavy precipitation.Therefore,in the process of the southeast wind and the southwest vortex rainstorm,the sudden increase of low-level jet index predicts the increasing intensity of precipi-tation.
万方数据
维普
