准地转理论基本问题回顾与讨论

准地转理论是大气动力学的中心问题之一,它提供了从大气动力学基本原理入手分析大尺度天气系统演变的方法。准地转理论有助于预报员理解中高纬度大尺度天气系统的三维结构,分析、预报天气系统的发展和移动,因此被称为短期天气预报的理论基础。准地转理论具有完整的理论体系,它包含了较多的基本假定,故容易导致对其中的一些基本问题的理解有混淆。本文从基础的动力学知识出发,对准地转理论的基本概念、基本近似、核心理论及其在实际天气预报过程中的应用作了回顾和讨论。内容包括:准地转运动与准地转近似定义、准地转运动理论的范畴、天气图上的大尺度运动、准地转运动理论与短期天气预报的关系、由斜压二层模式下的准地转理论对高空槽脊和地面气旋发展与移动的判断等。

Review and Discussion of Some Basic Problems of the Quasi Geostrophic Theory

Quasi geostrophic theory is the core of atmospheric dynamics, providing a method of analyzing the evolution of large scale weather systems according to the basic principles of atmospheric dynamics. This theory can help forecasters understand the 3D structures of large scale weather systems in the middle and hight latitudes, analyze and predict the development and movement of weather systems, so it is taken as the theoretic foundation of short term weather forecasts. The theory has complete theoretic system but involves some approximations that are prone to misunderstanding some of its basic problems. Proceeding from basic dynamic knowledge this paper reviews and discusses the basic concepts, basic approximations, the kernel theory of the quasi geostrophic theory and its application to the forecasting processes. The contents include definitions of the quasi geostrophic motion and quasi geostrophic approximations, the scope of the quasi geostrophic motion theory, the large scale motion in synoptic charts, correlations between the quasi geostrophic motion theory and short term weather forecasting, judgment of the development and movement of upper troughs and ridges as well as surface cyclones by the quasi geostrophic theory in baroclinic two layer model, etc.