长兴区域降水变化及趋势分析

利用长兴地区共9个雨量观测测站,1976—2011年的月平均降水量资料,运用趋势分析和EMD方法,根据长兴地区相应的地理特征,将该地区划分为平原和山区两区域,分别对两区域37 a来降水量变化的基本特征进行比较和分析,结果表明:①平原和山区年降水量距平百分率都呈略为下降趋势,山区下降趋势较平原更明显;②春季、夏季、秋季和冬季两地区的降水距平百分率的变化与年变化一致;③1990年代后期,平原地区降水距平百分率趋势的变幅明显大于山区,山区年代际降水量正距平出现的时间滞后于平原地区;④降水量变化方面,长兴地区呈现单调下降趋势,具有四类尺度的变化周期,分别是2～3 a,5 a左右,7～8 a及20 a左右。

Analysis of Precipitation Change and Trend for Changxing Region

There are nine rainfall observation stations in Changxing region,based on the geographic characteristics,Changxing region of Zhejiang Province is divided into two areas of the plain and mountainous area.The basic features of precipitation change in the two areas from 1976 to 2011 are analyzed and compared using the precipitation abnormity percentage and the empirical mode decomposition methods in this study.The results show: ①The precipitation abnormity percentage in the two areas shows a downward tendency,especially obvious in the plain area.②The changes of PAP in spring,summer,autumn and winter are identical with the annual change.③In the late 1990s,the amplitude of the precipitation abnormity percentage in the plain area is obviously bigger than that in the mountain area,and the PAP in mountainous area appears behind it in the plain area.④With respect of precipitation change,it is in the monotone downward tendency in the Changting Region,having four types of changing circle,namely 2~3years,5 years,7~8 years and 20 years respectively.