一次“高影响天气”的弱降雪过程的数值研究

该文对2001年12月7日下午北京的一次弱降雪天气过程进行了诊断分析和数值模拟研究。诊断结果表明:北京地区由于受500 hPa小槽东移及850 hPa东移小高压后部带来的来自东海和南海的偏南暖湿气流共同影响，造成降雪。数值模拟结果显示:MM5模式对这次降雪过程具有较好的模拟能力，不仅模拟出了北京地区的降雪量，而且对这次过程大尺度背景场的演变、触发机制和水汽源有很好的表述。利用诊断分析和数值模拟结果，对这次弱降雪过程引起交通大阻塞的可能因素进行了探讨，说明建立城市预警系统的迫切性。

A Simulation of a High Impact Weather Event

Owing to a light snowfall on December 7, 2001, traffic jams and congestion were occurred in Beijing. A diagnostic study and numerical simulations using MM5 were conducted on this high impact weather. The result of diagnosis shows that the weak trough at 500 hPa which moving eastward slowly and the 850 hPa high which brought in suitable water vapor from the South China Sea and East China Sea resulted in the happening of the light snowfall in Beijing. The results of the simulations indicate that the case can be simulated successfully by the numerical model MM5. The successive development of the background field, the trigger mechanism and the water source, as well as the snowfall in Beijing, were well reproduced. Based on the results of diagnosis and simulations, possible factors contributed to the traffic jams and congestion were also discussed. Thus study on city disaster meteorology, ~i.e. high impact weather and setting up a monitory and forecast system are inevitable, which can synthetically evaluate the impact of meteorology phenomena on city life in China.