基于动力因子的萍乡市一次区域性暴雨落区诊断分析

Diagnostic Analysis of Torrential Rain Area Based on Dynamic Parameters in Pingxiang City

利用常规观测资料、加密自动站资料,对2014年萍乡市一次区域性暴雨过程进行了分析。结果表明:低层西南急流,湿舌以及暖脊均伸向萍乡市,表明有明显的水汽输入、热力不稳定层结和湿斜压性,且萍乡市处于低涡暖切变南侧的强辐合区,是一次较易把握的暴雨过程,但萍乡市仅中部和北部的局部出现暴雨。利用ECMWF高分辨率资料计算了动力因子,对暴雨落区做进一步分析发现:1)广义位温水平梯度高值区和湿热力平流参数正、负中心交界面存在明显的热力不连续面、水平锋生和湿斜压性,与萍乡市中部和北部的降水有较好的对应关系。2)热力垂直螺旋度、水汽垂直螺旋度和热力位涡波作用密度的正、负中心交界面存在充沛的热量和水汽的输送、较强的垂直风切变、涡度矢量的扰动以及热量散度的扰动,对萍乡市中北部的强降水中心有较好的指示作用。

A regional torrential rain process in Pingxiang in 2014 was firstly analyzed by using the normal and intensive observation data. The analyses showed that the low level southwest jet,moisture tongue and warm ridge all extended to Pingxiang City,which meant the obvious import of vapors,thermodynamic unstable stratification and moist baroclinity,moreover,this city located in the stronger convergence area which is in the south side of the vortex warm share. In a word,this heavy rain process should be an easy case to grasp,but the heavy rain only occurred in the local parts of northern and central Pingxiang. So the further analyses on the heavy rainfall areas were taken out by computing the dynamic parameters using the high resolution data of ECWMF,and the results indicated as follows. Firstly,there were obvious thermal discontinuity,frontogenesis and moist baroclinity in the high value area of the generalized potential temperature（gpt）horizontal gradient and the interface between the positive center and the negative center of the moist thermodynamic advection parameter,which had a nice correspondence with the precipitation in central and northern Pingxiang. Secondly,the abundant transport of heats and vapors,the stronger vertical wind shear,the turbulent motion of vorticity vector and heat dispersion existed on the interface between the positive center and the negative center of the thermodynamic vertical helicity,the moisture vertical helicity and the thermodynamic potential vorticity wave-activity density,which had a better instruction on the intensity rainfall center in the north-central Pingxiang City.