叶尔羌河源流区近50年来年径流变化及其对气候变化的响应

  基于新疆卡群水文站和塔什库尔干气象站1959～2005年的观测资料，运用小波分析和统计分析相结合的方法，从多时间尺度研究叶尔羌河源流区近50年来年径流的非线性变化趋势，以及径流对气候变化的响应。结果表明: 1）年径流、气温和降水的主要变化周期几乎一致，年径流和年降水量都存在24年的主要变化周期，而年平均气温则是23年。2）年径流量表现出具有时间尺度依赖性的非线性变化趋势，与区域气候变化密切相关。3）年径流变化是区域气候变化响应的结果，从8（2³）年、4（2²）年和2（2¹）年时间尺度上来看，年径流量与年平均气温和年降水量之间存在显著的线性相关关系。

ANNUAL RUNOFF CHANGE AND ITS RESPONSE TO CLIMATE CHANGE IN THE HEADWATER AREA OF THE YARKAND RIVER IN THE RECENT 50 YEARS

Based on the data observed in Kaqung Hydrological Station(37°46'N,75°14'E) and Taxkorgan Meteorological Station (37°59'N,76°54'E)from 1959 to 2005,the characteristics of the annual runoff change and its response to climate change in the headwater area of the Yarkand River were analyzed using methods combined wavelet analysis and statistical analysis at different time scales.The time-series data of annual runoff,annual average temperature and annual precipitation in the recent 50 years was used to establish and test empirical models.The model analysis gives valuable information that can provide a better understanding of the nonlinear characteristics of the annual change of the headwater area at different time scales.The findings of this study is as follows.(1) A cyclic period of 24 years is detected of annual runoff and annual precipitation and a cyclic period of 23 years is detected of annual average temperature.Therefore,the cyclic patterns of the runoff and the regional climate factors are in agreement(about 24 years).These results suggest that the periodicity of the annual runoff of the headwater area of the Yarkand River is the result of regional climatic changes.(2) The wavelet decomposition of the time series runoff total at five time scales resulted in five variants of nonlinear trends.The nonlinear runoff pattern is found to be scale-dependent with respect to time.The runoff time series varied greatly at a smaller time scale(2 years),without showing any salient trend.However,the analyses conducted at a wider time interval (e.g.16 years or 32 years)reveals an increasing tendency.Using the method of wavelet decomposition,the nonlinear trends regarding the annual average temperature and annual precipitation series were detected.These findings suggest that temporal variations in the annual runoff of the headwater area might be propedy explained by the regional climatic changes.(3)The covariability between runoff and climate factors at multiple time scales can be examined via regression analysis based on the results of wavelet decomposition.The annual runoff exhibits a significant,positive correlation with the temperature and precipitation at the 2-years,4-years,and 8-year temporal scales.These results provide further evidence supporting the view that the nonlinear ascending trend of the annual runoff time series in the headwater area is strongly influenced by regional climate change.Many studies have showed that the annualrunoff,annual average temperature and annual precipitation were increasing in the recent 50 years in the Tarim River Basin.The present study indicates that increase in runoff was caused by increase of air temperature and precipitation.Moreover,air temperature is the main climatic factor affecting runoff in the headwater area of the Yarkand River.