冬季风爆发前西伯利亚高压的演变

The Evolution of Siberian High Prior to the Outbreak of Cold Air

本义是一次个例的诊断分析,应用FGGE-Ⅲ_b资料分析了1979年11月12—17日的东亚寒潮过程,着重讨论冷空气爆发前,位于两伯利亚的冷堆的增强过程,运用准拉格朗日坐标系的热量方程和涡度方程诊断了500hPa冷中心的温度变化和地面冷高压上空涡度演变的物理过程,分析结果说明,冷堆的增强与高空槽后急流中心前方出口附近的侧向环流有密切关系,开始时500hPa冷中心就位于此侧向环流的上升支附近,绝热冷却是冷堆加强的主要因子,即动力因子是主要的,冷高压上空的涡度变化与相对的涡度平流关系密切,它也与高空急流的相对位置有关,在地面高压加强的后期,散度项和平流项对于温度变化的贡献相反,但它们的垂直分布都有利于下沉运动加剧.因此,在分析预报中要密切注意忽流的动态. 本文的分析结果将有助于进一步理解冷空气增强的物理机制,也为寒潮过程的分析预报提供一定的参考.

The main objective of the present study is to estimate the contribution of different physical processes by calculating the quasi- Lagrangian heat and vorticity budgets of the Siberian high. The case selected in this study is a Siberian high prior to the outbreak during early winter, 12-17 November 1979. The results suggest that the dynamic process of the transferse circulation of the upper-level jet should be emphasized in the intensification of cold dome. The radiative cooling is probably a secondary factor compared with the adiabatic cooling. The results from the diagnose of the vorticity equation indicate that the relative vorticity advection is pronounced in the mid-and upper-troposphere. The deepening of downstream trough is essentially a transformation from shearing to curvature vorticity. The divergence term is considerable except at middle levels and has opposite tendency against the advective effect.The present result are helpful to understand the physical mechanism of the intensification of cold dome and the Siberian high.