相空间中划分大尺度异常雨型的进一步研究

FURTHER STUDY ON IDENTIFYING ANOMALOUS LARGE SCALE RAINFALL REGIMES IN PHASE SPACE

中文关键词:  相空间，雨型，夏季降水，聚类分析

英文关键词:Phase space, Rainfall regime, Summer rainfall, Cluster analysis.

中文摘要:

      使用1962～2001年的逐日台站降水资料，考察中国夏季大尺度低频降水的时空特征。对于20d以上的低频尺度降水异常，在前8个主要EOF模态支撑的相空间中，采用聚类分析方法划分了6种大尺度异常雨型：东北型、黄河型、秦岭淮河型、长江江南型、华南型和少雨型。分析表明，这些雨型的物理意义明确，具有较好的持续性，优于使用2维概率密度函数的划分结果，从而说明相空间中的聚类分型是整体性和区域性兼顾的划分方式，同时也证实了多维 相空间的不均匀性。统计结果显示，新雨型在季节内交替出现，能够反映出大尺度异常降水的低频演变特征，并且具有不同于季风雨带变化的特点。通过分析新雨型在历史上的分布情况，并与以往分型相比较，进一步反映出新雨型划分的客观性和合理性。

英文摘要:

      Using a 40-year daily precipitation dataset including 134 stations from 1962 to 2001, the large-scale distribution patterns of precipitation anomalies over China were investigated. In the phase space spanned by the first 8 EOFs generated from the 20-day low-pass filtered data, the six rainfall regimes (RRs) were id entified by applying a cluster analysis method, namely, the northeastern China regime, Yellow River regime, Qinling-Huaihe regime, Yangtze River with its south regime, Southern China regime, and rainless regime. Analyses show that the new RRs exhibit good persistence and evident physical sense, and excellently represent both of countrywide and regional features, which also demonstrate the inhomogene ity of multi-dimensional phase space. Furthermore, it is more important that th e new RRs can describe intraseasonal dynamic characteristics of large-scale rainfall anomalies,which is the most significant difference between the new RRs and the conventional season average rainfall patterns. On the other hand, the clim atic characteristics of daily distributions of the RRs events, as well as the 40-year panorama of the RRs occurring were also investigated, which further document reasonableness and objectivity of the RRs with intraseasonal variabil ity, and are likely to present more helpful information for short-range climate forecast, compared with other previous classical rainfall patterns.