中蒙干旱半干旱区降水异常的区域性差异及其年代际演变特征

The Spatial Variation in the Normal/Abnormal Precipitation over the Sina-Mongolia Arid/Semiarid Area and Its Decadal Transformation

本文利用1951~2005年间中蒙干旱半干旱区322个气象测站的月降水量资料,借助聚类和小波等统计分析方法对该区各月降水异常的区域性差异及其年代际演变进行了较为详细的分析,主要揭露了以下事实:1) 同降水量的年变化特征相近,降水空间分布形势也表现出明显的年变化,由春季到夏季,多雨区不断扩展,少雨区不断退缩,直到各地降水量均达到最大,然后由秋季到冬季,少雨区不断扩展,多雨区则不断退缩,直到降水量恢复到全年的最小值,使得1年明显成为降水空间分布变化的一个周期。2) 通过聚类分析给出1951~2005年间各月降水异常的典型空间分布型及其出现的年份和频次,说明不同月份,即使属同一季节,其降水异常的典型空间分布型也有很大差异,不同月份典型空间分布型出现的年份也少有规律可循。3) 中蒙干旱半干旱区降水异常的区域性差异存在着明显的年代际演变。4) 通过小波分析给出一些主要区域逐月降水量年代际变化的主要周期性特征,结果表明同一区域,不同月份,即使属同一季节,其降水量变化的周期和位相也很不同。

Based on the monthly precipitaiton data during 1951 - 2005 for the selected 322 meteorological gauge stations over the Sina-Mongolia arid and semiarid area, the spatial variation in the normal/abnormal precipitation and its decadal transformation for each month have been analyzed in detail utilizing the statistical clustering and the wavelet analysis, disclosing the following facts: 1) Being similar to the monthly precipitation, the spatial distribution of the precipitation is also displaying its argular yearly variation apparently, with the wet area extending continuously and the arid area con-stracting from spring to summer, till the precipitation reaching the maximum at each station, and then, from autumn to winter, the arid area extending and the wet area constracting continuously, till the precipitaiton going back to the minimum at each place, so, one whole year is apparently a circulation of the spatial precipitaiton distribution. 2) The typical spatial distribution patterns of the abnormal monthly precipitation and their appearing years and frequencies during 1951 - 2005 have been found based on the statistical clustering analysis, showing that, the typical spatial distri-bution patterns and their appearing years and frequencies are all largely different from one month to another month even in the same season. 3) There is apparently a decadal transformation in the spatial variation of the normal/abnormal pre-cipitaiton over the Sina-Mongolia arid and semiarid area. 4) The major periods existing in the decadal variation of the precipitation for each calendar month and each major area have been found by the wavelet analysis, disclosing the pe-riodicity and the wave in the precipitaiton variation at some certain place will be different from one month to another even in the same season.