阻塞过程的正、斜压涡度拟能场诊断研究

THE STUDY OF THE BLOCKING CIRCULATION DEVELOPMENT EXCITED BY THE BAROTROPIC AND BAROCLINIC ENSTROPHY INTERACTION

应用正、斜压涡度拟能方程,对1998年6月3～11日发生在鄂霍次克海的一次阻塞环流进行诊断。结果表明:阻塞区内总涡度拟能和正压涡度拟能具有显著的变化,它清楚地揭示了阻塞过程中酝酿、维持和崩溃阶段中的不同特征,而正、斜压动能所显示的阻塞过程的变化特征则不明显。正、斜压涡度拟能场相互转换及阻塞区内外正、斜压涡度拟能场的净通量机制是鄂霍次克海阻塞环流建立和维持的两项主要因子。其过程是:首先通过斜压涡度拟能净通量机制,使斜压涡度拟能增长;又通过正斜压涡度拟能场的转换机制将增长的斜压涡度拟能转为正压涡度拟能;与此同时,通过正压涡度拟能净通量机制使正压涡度拟能增长。这两种不同的机制相互结合,从而使正压涡度拟能增长和维持,形成阻塞环流。而斜压涡度拟能增长甚微。

Using barotropic and baroclinic enstrophy equations, an Okhotsk blocking occurring from June 3～11, 1998 is diagnosed. Results show that total enstrophy and the barotropic counterpart vary remarkably, clearly revealing different characteristics in fermenting, maintaining and decaying phases of the blocking, and barotropic and baroclinic kinetic energy shows insignificant features for the blocking development. The inter-transformation of the barotropic and baroclinic enstrophy and their net flux generating mechanism in and outside the blocking region are two major factors for its establishment and maintenance, which occurs in such a way that baroclinic enstrophy is made to grow through the net flux mechanism, followed by converting increased baroclinic enstrophy via the mechanism into barotropic enstrophy and through their transformation mechanism the increased barotropic is converted into baroclinic enstrophy; at the same time barotropic enstrophy is made to increase via its net flux generating mechanism. The combination of the two mechanisms causes barotropic enstrophy increase and remain constant, leading to the formation of the blocking circulation but, in contrast, baroclinic enstrophy increases very little.