摘要
对 2 0 0 1年 1 2月 7日一次引发北京交通堵塞的降雪过程成因作了模拟研究。模拟结果显示PSU/NCAR的MM5有可能模拟出此次北方较弱的降雪过程 ,模拟的降雪量、落区以及持续时间与观测较一致。在成功模拟的基础上 ,利用模式输出的时空分辨率较高的资料 ,对此次降雪的发生、发展和水汽输送过程等进行了分析 ,结果表明 :( 1 )降雪发生前对流层中层先出现饱和 ,而低层并未饱和 ,这种弱降雪的产生似乎并不需要中低层有深厚的湿层存在 ;( 2 )此次降雪是由对流层中层快速移动的短波槽和近地面出海高压后部的回流共同影响的结果 ,近地面的高压回流主要对增加低层的湿度有贡献 ,槽前的西南气流将水汽由南向北输送到华北地区 ,辐合引起的上升运动又将水汽输送到对流层中上层 ,槽前的水汽输送和辐合上升是此次降雪过程的触发机制之一 ;( 3)华北地区大气中可降水量达到 7mm以上时 ,就可能有弱降雪发生 ,并有可能根据可降水量判断降雪的维持时间 ;( 4 )冰相云物理过程对成功地模拟降雪是不可忽视的。
The light snowfall with precipitation amount of 1.8 mm d -1 occurred in North China (including Beijing) on 7 December 2001 and the serious traffic jam appeared. To better understanding of the snowfall process and its predictability, the PSU/NCAR mesoscale model (MM5) has been employed to replicate the process.The simulation results show that the location, strength and duration agree fairly well with the observation although some deficiencies exist.On the basis of success simulation, the occurrence and evolution of the light snow and its physical processes are investigated.The analyses indicate: the quick-moving short trough at middle layer and its convergence, upward may initiate this light snowfall process, the low level and middle level troposphere are the saturated and unsaturated layer prior to the snowfall respectively.And with the evolution of snowfall, humidity at low level air increase gradually.It is suggest that deep moist layer is not necessary to the formation of light snowfall.It is possible to produce light snowfall while precipitation water exceeds 7 mm in North China.In addition, ice-phase explicit cloud process is a very important physical process for the snowfall simulation.
出处
《气候与环境研究》
CSCD
2003年第4期387-401,共15页
Climatic and Environmental Research
基金
中国科学院大气物理研究所知识创新工程 (二期 )面上基金
国家重点基础研究发展规划项目"我国重大灾害天气机理和预测理论研究" (G1 9980 40 90 0 )资助
