北京地区一次小雪天气过程造成路面交通严重受阻的成因分析

通过对2001年12月7日降雪天气过程与历史同期降雪过程的比较以及对降雪过程中不同物理介质路面温度变化的观测研究表明,"12·7"北京地区路面交通严重受阻是由于特殊的时间、特殊的城市和特定的路面状况等多种非气象因素与"落雪成冰"的气象环境条件共同作用造成的.这种气象环境条件的形成是由于降雪过程中,雪面、路面与近地面大气之间复杂的热量交换和相互影响的结果:降雪开始时,由于雪片的吸热作用,造成路面和紧贴地面的大气温度下降,而近地面层气温的下降,反过来造成路面温度进一步降低,在两者的共同作用下,地表落雪迅速形成冰面.冰面的反射作用又进一步加速了气温、尤其是近地面层气温的下降,不断降低的气温使得冰层硬度加强、厚度迅速增加.作者还通过天气诊断和数值模拟分析,对这次降雪天气过程的物理机制进行了简单的讨论,认为这次降雪天气很可能是由对流层中层快速移动的高空槽、地面弱倒槽和近地面层弱的偏东气流共同影响而产生的.

An Analysis on Serious City Traffic Trouble Caused by Light Snow

In this paper, the basic weather condition, which caused serious traffic trouble in Beijing city, has been analysed by comparing the history situation with the light snow happened in 7 December 2001 It has been proved that the disastrous event is related with interaction between the special city circumstance and serious weather phenomenon which happened when the fallen snow rapidly froze, and this serious condition is caused by sophisticated inter|effect between the temperature on different material surface and air temperature on different level It has been found that the temperature's falling of the road surface and near|surface's air is caused by the snow's endothermic reaction during initial stage, in return, the lower air temperature will accelerate falling of the road surface temperature, and the first ice layer is come to being by this positive feedback However, its reflection of heat will make near|surface's air temperature decrease more Based on the results of numerical experiment and weather analysis, the possible mechanisms of this snow have been studied It is considered that the light snow is possibly caused by interaction among rapid moving trough in troposphere, weakly air pressure trough and thin east|flows on near|surface