2010年3月14日华北强降雪的模拟和特征分析

本文主要对2010年3月14日华北强降雪进行了模拟、诊断和特征分析。此次华北降雪在中、低层主要受西风槽、低涡及切变线影响，蒙古气旋东移加强、地面倒槽发展及东风廽流建立构成了有利地面天气形势，西北涡、强势的西南暖湿气流及稳定的环渤海高压对此次强降雪至关重要。垂直速度、散度、涡度、螺旋度的分布和演变反映出在此次降雪过程中，强降雪区出现了很强的辐合上升运动，降雪区上空螺旋度呈“下负上正”的垂直结构，螺旋度大值区对应强降雪中心；而锋生条件为降雪的形成和维持提供了一定的能量；相对湿度和水汽通量散度的分布说明强降雪区整层湿度较大，且水汽供应充足。

Simulation and Diagnosis on a heavy snowfall event over North China on 14 March in 2010

In this paper, heavy snowfall event is simulated and investegated over North China on 14 March in 2010. The results show that the heavy rainfall process was well simulated by the meso-scale numerical model MM5. Vortex and trough at mid-low-level have main effect on the snowfall. Mongolia cyclone moving eastward and intensifying, reversed trough developing, close low circulation and east backflow founding in surface are propitious to the heavy snowfall. The Northwest vortex, strong southwest warm moist stream and stable high around Bohai Sea play key roles on the snowfall. According to the change of vertical velocity, divergence, vorticity, helicity and frontogenetic function, it is obviously found that atmosphere converged and ascended in heavy snowfall area. The vertical profile of helicity over heavy snowfall area shows the opposite pattern, with negative in the low-middle-level and positive in upper-level of troposphere. The large negative helicity area corresponded to center of snowstorm. Moreover, frontogenetic condition provided energy for snowfall forming and maintaining. Distribution of relative humidity and moist flux divergence shows that there was high relative humidity and the strong moisture convergence over the heavy snowfall area and water vapor importing was enough.