2008年初南方雨雪冰冻灾害天气的大气层结和地面特征的数值模拟

Numerical Simulation on Stratification and Surface Features of Freezing Rain and Snow Storm over Southern China in January 2008

冬季的雨雪预报,尤其是冻雨的预报涉及多种尺度系统与复杂物理因素的影响。为了探讨这方面的问题,作者采用中尺度数值模式MM5对2008年初我国南方持续性雨雪、冰冻灾害天气中的1月26～29日过程做了模拟试验研究,并根据模拟结果对1月26～29日期间的水汽条件、地面特征和大气层结条件等重要环境条件进行了分析。分析指出,模拟结果能基本再现冬季这种持续性过程的降水带分布;长江或江南地区的准静止锋的存在,水汽在锋前对流层低层辐合,并沿锋面向上爬升凝结,爬升到达的高度和强水汽带的宽度与观测基本一致。模式还能再现有利于冻雨产生的层结条件,包括中层冻结层、暖层、逆温层和地面温度0℃线的位置;研究指出,利用模式输出的层结、地面条件以及降水状况可以大致得到冻雨可能发生的范围。

The PSU/NCAR MM5 model is utilized to simulate the severe freezing rain and snow storm during 26-29 January 2008.And then,the simulation results is used to diagnose the moisture flux,surface temperature,stratification conditions for freezing rain occurrence.The results are that,the numerical model could reproduce the distribution of precipitation band during 26 to 29 January 2008.The east-west oriented quasi-stationary front located along Yangtze River Basin is favorable for the transportation and convergence of water flux.The strongest moisture convergence occurrs ahead the front at low-level and then climbs slantly along the front to middle troposphere.The lifting height and width of moist flux along front surface is consistent with the observed,but the intensity is slightly weaker than the latter.The model also reproduces the stratification and surface features,including inversion layer,warm layer,0 ℃ isoline in surface ground temperature field.It is suggested that the freezing rain area could be predicted by composite consideration of stratification,surface condition and precipitation.