WRF模式对一次河西暴雪的数值模拟分析

利用NCEP再分析资料,使用WRF模式模拟了2005年3月14~15日出现在甘肃河西西部(祁连山西段北坡)的一次暴雪天气过程。结果表明:WRF模式能较好地模拟出暴雪的区域,对这种中尺度天气系统具有良好的预报能力。在这次暴雪过程中,地面冷锋、低空风场切变线,以及与高空强锋区相对应的高空急流的合理配置加强了暴雪区的垂直环流的发展,使降雪区对流发展;出现暴雪时最大辐合层在600 hPa附近,500 hPa以上表现为一个深厚的辐散层。随着强降雪的开始,降雪区近地面层由辐合变为辐散,反映出由于能量释放,降雪的影响系统开始逐渐消亡;在降雪过程中始终伴随着中小尺度特征的强烈的垂直上升运动,最大上升速度层在500~400 hPa之间;降雪的水汽来源于西风气流,水汽输送在600 hPa最强。600 hPa的强水汽输送和强辐合保证了产生强降雪必需的水汽条件。

Simulation and Analysis of Heavy Snowfall in the Hexi Corridor with WRF Model

Numerical simulation is made with the new generation numerical model-WRF(Weather Research and Forecast) on a heavy snow process happened in the Hexi Corridor during 13~16 March 2005.It is clear that the WRF model can make good simulation about the snowfall distribution.Main conclusions are as follows:(1) The appropriate collocation of cold front of surface,shear of lower-level wind field and upper-level jet enhances the development of vertical circumfluence.(2) There is the maximum convergent 600 hPa,and the divergent is above 500 hPa when the heavy snowfall is happened.With the beginning of the snowfall,the mesoscale synoptic system fades gradually.(3) There is intense mesoscale ascending motion in the whole snowfall process,and the ascending motion between 500~400 hPa is the strongest.(4) The westerlies(especially 600 hPa) supports enough water vapor to the area of snowfall.