一次双急流型沙尘暴过程的数值模拟与诊断

利用MM5模式对2001年4月8～9日的双急流型沙尘暴天气过程进行了数值模拟和诊断分析,结果发现:此次沙尘暴过程中有强的西风动量下传,动量下传主要由北支急流完成;在沙尘暴发展旺盛阶段,南、北两支急流低层的南风和北风分量之间产生的辐散促进了高层动量下传,而高层南北两支急流南风分量的加强和贯通引导南方暖湿气流向北输送,抑制了沙尘暴的发展.南北两支急流的共同作用是造成该次沙尘暴的重要原因,北支急流产生了直接的作用,南支急流有间接的影响.250 hPa两支MPV1正的大值位涡区与南、北两支急流有很好的对应关系,在沙尘暴区域前部,对流层高层存在对称不稳定.

Numerical Simulation and Analysis of a Double-jet-airstream Sandstorm

In this paper, a sandstorm occurred during the period from April 8 to 9, 2001 is simulated and analyzed using MM5 model. The results reveal that there was a strong westerly momentum transferring to the lower airstream in this sandstorm, and it was dominated by the north jet airstream; the divergence between north wind and south wind at the lower north and south jet airstreams enhanced the momentum transferring to the lower airstreams and the development of sandstorm, but the enhancement and connection of the south wind component of the upper north and south jet airstrearns brought about the northward movement of the warm-humid airstream from the south, thus the development of the sandstorm was restricted. The joint effect of both north and south jet airstreams was the main cause of the sandstorm, and the occurrence of the sandstorm was affected directly by the north jet airstream and indirectly by the south jet airstream. The rotation direction of the axles of both north and south jet airstreams was affected by the ageostrophic wind latitude components. The change of MPV1 accorded well with the development of the upper jet airstreams and the sandstorm, and there was a symmetrical labilization in the upper troposphere over the front of the sandstorm area.