相空间中划分大尺度异常雨型的初步研究

文中针对以往雨型研究中的不足 ,从动力学角度将相空间引入到大尺度异常雨型的划分 ,通过估计EOF相平面上的概率密度函数、并确定局部极大值区域来划分主要雨型。分析表明 ,新雨型不仅再现了传统的 3类雨型特征 ,还得到了其他分型 ,并且能够反映出异常降水分布的季节内低频变化 ;分别采用 10和 2 0d低通滤波数据划分的雨型形态比较接近 ,但其种类、持续性和季节内分布等特征存在一定差异 ;雨型的气候分布与季风雨带有一定对应关系 ,其形成与夏季风异常关系密切。通过对简单直观的二维相平面问题的探讨 ,不仅证实了在相空间中划分大尺度雨型的可行性 ,也为进一步在高维空间中讨论雨型问题提供了依据。

PRIMARY STUDY ON IDENTIFYING ANOMALOUS LARGE-SCALE RAINFALL REGIMES IN PHASE SPACE

In order to overcome the limitation of traditional rainfall patterns in reflecting intraseasonal variation, new anomalous large-scale rainfall regimes are identified in this paper,by introducing the phase space in terms of a dynamical point of view, and estimating probability density functions in the phase plane spanned by the first two EOFs, as well as examining local maximum regions. The analysises show that the new rainfall regimes reproduce not only the three kinds of traditional rainfall patterns and the others, but also describe the intraseasonal features of anomalous precipitation distributions, which evidently can use the daily precipitation anomalies involving the very important low-frequency components in short-term climate forecasts. On the other hand, the rainfall regimes from the 10-day and 20-day low-pass filter data,respectively, are approximately accordant, though there exist also some obvious differences between them such as the characters of classification, duration, and intraseasonal distribution, which exhibits the distinct contributions of the two low-frequency scales to rainfall regimes. Furthermore, in the present paper, the climatological distributions of rainfall regimes are in certain agreement with usual monsoon rainbelts in the flooding seasons, and the formation mechanism of rainfall regimes are closely associated with the corresponding summer monsoon anomalies. By investigating the visual and intuitional problems of 2-dimension phase plane,it is verified not only the rationality and feasibility of identifying large-scale anomalous rainfall regimes in the EOF phase space, but also presented the evidences of identifying rainfall regimes in multi-dimensional phase space.