1961—2016年西宁市极端降水事件变化特征

Variation features of extreme precipitation events in Xining City from 1961 to 2016

为研究西宁市极端降水事件变化规律,利用西宁气象站1961—2016年逐日降水量序列资料,计算得出年总降水量、5日最大降水量、极端降水量、日降水强度、持续降雨日数及大雨日数等6个极端降水指标的年际序列,应用线性倾向估计法、滑动平均法、Mann-Kendall非参数检验法、Morlet小波分析、相关性分析等方法分析各极端降水指标的变化趋势、变化周期及各指标间变化一致性。结果表明,近56年间西宁市各极端降水指标呈波动式增加趋势,其中PRCPTOT的增加趋势显著,而其余各指标变化趋势不显著;PRCPTOT、RX5day、R95及SDII序列在整个研究时段内均存在明显的突变现象,其中在1960年代后期及1970年代中期RX5day与R95发生了一致的突变,在1980年代末和1990年代初,PRCPTOT、RX5day与SDII发生了一致的突变;在近56年间各极端降水指标的振荡变化均存在明显的主周期,其中除SDII外,从1990年代开始各指标多存在约11—13年的主周期,SDII及CWD的振荡变化均在整个研究时段上存在40年及29年左右的主周期;各极端降水指标与总降水量均呈一致的正相关性,对总降水量的变化具有较好的指示作用,RX5day、R95、SDII及R20 mm四个指标相互之间均存在显著的正相关性。研究结果可为区域水资源规划及洪旱灾害防御提供参考。

In order to study the variation law of the extreme precipitation events in Xining City,the inter-annual series of 6 extreme precipitation indexes,i. e. total annual precipitation,five days-maximum precipitation,extreme precipitation,daily precipitation intensity,persistent rainy days,heavy rainy days,etc.,are calculated and obtained through the serial data from 1961 to 2016 recorded at Xining Meteorological Station,and then the variation trends of all the extreme precipitation events,the variation cycles and the variation consistency among all the indexes are analyzed with linear trend estimation method,moving average method,Mann-Kendall test method,Morlet wavelet analysis and correlation analysis. The result shows that all the extreme precipitation indexes of Xining City exhibit the trends of fluctuated increases during the period of near 56 years,in which the increasing trend of PRCPTOT is significant; however,the variation trends of all the other indexes are not so obvious. Obvious mutations of PRCPTOT,RX5 day,R95 and SDII series are there in the period of time for the study,in which consistent mutations of RX5 day and R95 occur in the late-1960 s and the mid-1970 s,while consistent mutations of PRCPTOT、RX5 dayand SDII occur in the late 1980 s and the early1990 s. Obvious principal cycles are there in the fluctuated variations of all the extreme precipitation indexes during the period of near 56 years,in which the principal cycles of about 11—13 a are there for most of all the indexes from the beginning of 1990 s and the principal cycles of about 40 a and 29 a are there in the fluctuated variations of both SDII and CWD in the period of time for the study. All the extreme precipitation indexes exhibit positive correlations with those of the total precipitations,which has a better effect for indicating the variation of the total precipitation; moreover,significant correction is there among the indexes of all RX5 day,R95,SDII and R20 mm. The study result can provide references for both regional water resources planning and preventions of flood and drought disasters.