冷涌结构及冷涌期中低纬环流相互作用的数值试验

THE NUMERICAL STUDY OF COLD SURGE STRUCTURE AND NTERACTION BETWEEN MIDLATITUDES AND TROPICS DURING COLD SURGE

摘要:

本文利用1982年12月下旬一次冷涌过程的数值试验结果,分析了冷涌的结构并初步讨论了冷涌期中低纬环流的相互作用。结果表明,冷涌仅在近地面反映清楚,水平流场上表现为由大地形激发的开尔文波引起的东北大风沿青藏高原东侧迅速南下,而冷涌前沿则是以重力波特征向南传播。Hadley环流随冷涌南进不断加强。冷涌在涡度场和散度场上分别为一条状北倾的正涡度区和辐合区,它对应于冷锋南下时造成的上升运动区。冷涌能引起赤道地区的扰动加强和中纬度对流层高层西风急流的增强。冷涌期中低纬地区能量增大,通过能量的频散作用把中低纬环流连结起来了。

Abstract:

In a numerical experiment with a cold surge in Dec. 1982,its structures are examined and interactions between middle and low latitudes circulations at the time discussed preliminarily. The result shows that the horizontal flow of the cold surge,best-defined near the surface,is seen as a strong and rapid northeasterly running south along the east side of the Tibesan Plateau and modes of gravity wave propagating south off its front edge. Meanwhile,the Hadley cell keeps intensifying with the southward advance of the surge,whose north-inclined columns of positive vorticity and convergence are consistent with the updrafts of a cold front associated with it. It intensifies equatorial disturbances and the westerly jet at upper troposphere in mid-latitudes. Simultaneously increased energy links up middle and low latitudes circulations through its dispersive effects.