西南喀斯特地区降雨集中度及其变化特征分析-以乌江流域中上游为例

本文采用乌江流域中上游地区1951～2008年的逐日降雨资料,分析26个气象站点年雨量、连续3日、5日、7日无雨日次数、最大日降雨统计特征,以及日降雨集中度指数CI,并利用非参数Mann-Kendall检验分析日降雨集中程度以及降雨统计特征变化趋势。结果表明,近58年以来,虽然该地区年雨量变化趋势不明显,但各站日降水量集中度呈现加大的趋势,且77%站点增加趋势显著。研究也表明,连续3日、5日、7日无雨日次数以及最大日降雨量也呈现增加趋势,日降水量集中度与最大日雨量相关程度高,说明该地区暴雨和干旱发生频率增加趋势明显。

Analysis of Daily Rainfall Concentration and Its Change Characteristics in Southwestern Karst Regions-A Case Study of Wujiang Catchment

In this paper,the observed daily rainfall data from 1951 to 2008 of 26 meteorological stations,which were located in the upper reaches of the Wujiang River,were analyzed to get the statistical characters such as annual precipitation amount,the times of annual occurrence of successive 3-day,5-day and 7-day no-rainfall periods,the maximum daily rainfall amount as well as the precipitation concentration index.And the nonparametric Mann-Kendall(M-K) test was used to identify the trends of precipitation concentration index and other daily rainfall's statistical characters.The result showed that annual precipitation trend was indefinite for the past 58 years,but the station annual precipitation concentration index has a marked upward trend,and about 77% of the stations had a significantly increasing trend.The study also showed that a significant increase could be seen in the times of annual occurrence of successive 3-day,5-day and 7-day no-rainfall periods and the maximum daily rainfall amount series.At the same time,the precipitation concentration of daily rainfall series and the maximum daily rainfall amount series had a high degree of correlation,which indicated obviously increasing frequency trends of rain storms and droughts in this region.