A Study on Snowfall in Beijing on 7 December 2001
北京"12·7"降雪过程的分析研究

A light snowfall with precipitation amount of 1.8 mm/ d occurred in Beijing on 7 December 2001 and the serious traffic jam appeared. For better understanding of the snowfall process, the circulations, synoptic systems have been investigated. The conclusions are as follows: (1) The moisture transportation in PBL by the eastern current from the Yellow Sea and East China Sea pay a very important role in the process. (2) The trough (or short wave) at 500 hPa from West China overlay on the maximum area of moisture flux convergence to initiate and enhance the upward motion. (3) It is very difficult to predict successfully the snowfall in Beijing of 7 December 2001 due to the shallow of the systems, however, the higher time and space resolution data from the 325 m meteorological tower can reveal the finer and detailed structure of snowfall process. (4) It is suggested that more special data is needed and the cloud physical processes, including stratum cloud, and planetary boundary layer, in the numerical model should be improved farther, if the better prediction is expected. (5) The observation and prediction on real time ground temperature should be conducted so that condition of the roads can be estimated earlier. (6) In addition, some problems beyond meteorology, for example, roads and bridges construction, traffic management and so on should be paid more attention to in the future.