孟加拉湾季风爆发对南海季风爆发的影响Ⅱ:数值试验

IMPACTS OF THE ONSET OF THE BAY OF BENGAL MONSOON ON THE ON SET OF THE SOUTH CHINA SEA MONSOON. PART II: NUMERICAL EXPERIMENTS

通过数值试验研究了孟加拉湾季风爆发期间该地区旺盛的对流凝结加热对南海季风爆发和副热带高压“撤出”南海的影响,结果证明在孟加拉湾地区引入模拟的对流凝结潜热使该地区出现了强烈的上升运动,引起了孟加拉湾季风的爆发。同时由于对凝结加热的非对称Rossby响应,在南海北部导致西风出现和增强及垂直上升运动。因低层水汽平流的共同作用下,在南海北部引起了对流的发展。而正是南海北部的凝结加热促使南海地区温度经向梯度逆转,使副热带高压脊面的倾斜从冬季型转为夏季型,即低层的副热带高压减弱南移。最后当对流在南海地区发展起来时,副热带高压移出南海地区。

This study investigates the physical link between the convection associated with the BOB monsoon vortex and the SCS summer monsoon onset, as well as the mechanism of the evolution of the low - level subtropical anticyclone over the SCS through numerical experiments. It is shown that introduction of heating over the BOB results in vigorous convection over the BOB, and the BOB monsoon onset, as well as the development of westerlies and vertical ascent over the northern SCS region due to an asymmetric Rossby-wave response. Together with the low-level moisture advection, convection is induced over the northern SCS. It is the condensation heating over the northern SCS that causes the overturning of the meridional gradient of temperature over the SCS. Consequently the subtropical anticyclone in the lower troposphere over the SCS weakened gradually. Eventually as convection develops over the entire SCS domain, the subtropical anticyclone moves out of the region.