一个新动力因子在登陆台风“凤凰”强降水过程中的应用

根据波动和风场辐合辐散与登陆台风强降水密切相关的特点,利用高分辨率的数值模拟资料,采用分别表征强降水区波动特征和辐合辐散特征的两个动力参数——位势散度波作用密度和散度垂直通量,对登陆台风"凤凰"的强降水过程做诊断分析;同时结合波扰动和辐合辐散两特征,发展了一个新的物理量——热力切变散度参数,并据此对台风"凤凰"的强降水过程做进一步诊断分析,结果表明在整个研究时段内,地面雨区被热力切变散度参数的异常值区始终覆盖,二者具有较一致的空间分布和时间演变趋势。基于GFS(Global Forecast System)预报产品的动力释用分析表明,利用数值预报场计算的热力切变散度参数的强信号出现在强降水区,而弱信号出现在非降水区,该参数对强降水落区有较好的指示作用。

Application of a new dynamic factor on the strong precipitation of landing typhoon "Fung-wong"

Baed on the characteristic that there are close relations between the wave, convergence and divergence of wind field and the strong precipitation of landing typhoon, with the high-resolution simulation data, using two dynamic parameters:potential divergence wave action density and divergence vertical flux(they represent the wave features and the convergence and divergence features of strong precipitation area, respectively), this paper carried out a diagnostic analysis on the strong precipitation of landing typhoon "Fung-Wong".Combining the wave disturbance features and the convergence and divergence features, a new physical quantity:thermal shear divergence parameter is defined.Based on the parameter, a further diagnostic analysis is carried out on the strong precipitation of "Fung-Wong".Results show that the rainfall area is always covered by the abnormal value area of thermal shear divergence parameter, and they have the similar spatial distribution and time evolution trend.The dynamic interpretation analysis of GFS(Global Forecast System) forecast products shows that the strong signals of thermal shear divergence parameter locates in the rainfall area and the weak ones in the non-rainfall area, which has a good indicative meaning for forecasting strong precipitation area.