空间非均匀加热对副热带高压形成和变异的影响──Ⅲ:凝结潜热加热与南亚高压及西太平洋副高
THE EFFECT OF SPATIALLY NONUNIFORM HEATING ON THE FORMATION AND VARIATION OF SUBTROPICAL HIGH PART Ⅲ:CONDENSATI0N HEATING AND SOUTH ASIA HIGH AND WESTERN PACIFIC SUBTROPICAL HIGH
-
摘要: 通过理论分析和数值模拟,研究了降水所致凝结潜热影响副热带高压带断裂的物理机制。基于全型垂直涡度方程的尺度分析指出,强的对流凝结加热的垂直梯度的变化,导致副热带地区对流层高层和中低层的高低压分布呈现出反位相。数值试验证实凝结潜热是决定东半球夏季副热带高压位置和强度的关键因素:东亚季风降雨所致凝结潜热加热使高层南亚高压位于加热中心西侧,中层西太平洋副热带高压位于加热中心东侧。通过定常波的传播,副热带地区的凝结潜热加热对中高纬天气的形成和维持有一定影响。Abstract: The effect of condensation heating on the formation of enclosed subtropical anticyclone centers is studied using theoretical analysis and numerical simulation. The complete form of vertical vorticity tendency equation is employed for the analysis. It is found that, due to the variation of the vertical gradient of strong convective condensation heating, the distribution of cyclone and anticyclone in upper troposphere is out of phase with that in the middle and lower level in the troposphere. This is confirmed by numerical experiments. It is concluded that condensation heating is a key factor for the formation and location of summer subtropical high in the eastern hemisphere. The latent heating released by the monsoon rainfall forces the 200hPa South Asia high on the western side of heating center, and the 500hPa Western Pacific subtropic high on the eastern side of the center. Circulation in mid-high latitudes is also affected by the latent heating in subtropical area through the propagation of Rossby wave.