吉安市一次持续强降雨过程的水汽与垂直运动诊断分析

Diagnostic Analysis of Water Vapor and Vertical Motion in a Continuous Heavy Precipitation Process in Ji'an City

综合使用探空资料、地面观测资料以及NCEP (National Centers for Environmental Prediction) 10×10再分析资料等,对2019年6月上旬吉安市持续强降雨过程进行诊断分析,结果表明:高空低槽、中低层急流和切变线是直接影响系统,地面冷锋与边界层辐合切变为强降雨有利动力触发机制;强降雨期间吉安上空比湿接近江西省汛期区域性暴雨天气发生的阈值条件;7日过程垂直上升运动更集中且伸展高度高,而9日过程水汽则更充沛;两次强降雨过程降雨峰值均发生在水汽通量辐合区与上升运动中心叠加时段,当850~925 hPa出现水汽通量辐散中心或是出现下沉运动时,强降雨过程则趋于结束。

Sounding data,surface observation data and NCEP(National Centers for Environmental Prediction)reanalysis data with horizontal resolution of 1-degree by 1-degree were used to diagnose and analyze the continuous heavy precipitation process in Ji'an City in early June,2019.The results showed:the upper level low trough,the middle and low level jet and the shear line were the direct affecting system.The surface cold front and the boundary layer convergence were the favorable dynamic trigger mechanism of heavy precipitation.The specific humidity over Ji'an during heavy precipitation was close to the threshold condition of Regional Rainstorm in Jiangxi Province in Flood Season.On June 7th the vertical upward motion was more concentrated and the extension height was higher,while on June 9th the water vapor was more abundant.The rainfall peaks of the two heavy rainfall processes occurred in the period of superposition of the water vapor flux convergence area and the ascending motion center.When the water vapor flux divergence center or descending motion appeared at 850~925hPa,the heavy rainfall process tended to end.