1951—2009年北京市降水变化情势分析

Analysis of precipitation variation trend in Beijing City from 1951 to 2009

建立北京市1951—2009年的降水变化时间序列,采用经验模态分解(EMD)方法求出该序列的本征模态函数(IMF),分析原序列内在的多尺度振荡变化;综合运用Mann-Kendall法和R/S法分析原序列的突变以及未来趋势特征。结果表明:北京市降水变化序列主要由IMF1、IMF2和IMF3这3个本征模态构成,3～4a、5～6a、14a尺度的振荡变化对整个变化起主要作用;短期内,北京市年降水量有在波动中减少的趋势。1951年来,降水序列整体上呈减少趋势;减少的突变年份是1994年,2005年以后降水显著减少。从M-K与R/S方法的综合分析来看,在未来的长时间尺度上,北京市的年降水量整体上将在波动中不断增加。

A time series of precipitation variation in Beijing City from 1951 to 2009 was built. The intrinsic mode functions （IMF） of the time series were calculated and the intrinsic multi-scale oscillation change was analyzed using the empirical mode decomposition （EMD） method. A combination of the Mann-Kendall method and the R/S method was used to analyze the features of mutation and the future trend of the original series. The results show the following： The time series of precipitation variation mainly consists of three intrinsic modes, including the IMF1, IMF2, and IMF3. The whole variation is mainly controlled by the oscillation variations at the scales of three to four years, five to six years, and 14 years. The precipitation over Beijing City has a declining trend in a short period. The time series of precipitation has shown a declining trend in general since 1951. The from 2005 onward. Based on an integrated analysis over Beijing City will constantly increase in general precipitation abruptly decreased in 1994 and decreased significantly with the Mann-Kendall and R/S methods, the annual precipitation over a long time scale in the future.