1957—2007年雅鲁藏布江中游河谷降水变化的小波分析

Wavelet analysis of precipitation in the middle reaches of the Yarlung Zangbo River from 1957 to 2007

通过对近51 a雅鲁藏布江中游河谷地区4个气象站逐日降水资料进行等权平均取值,采用气候倾向率和小波分析法,研究了不同时间尺度下近51 a降水变化趋势及周期特征。结果表明:研究区降水量以20世纪80年代为最少,2000年后年降水量与20世纪90年代和60年代基本持平。夏季和秋季降水量年代际变化与年降水量的变化基本一致。近51 a降水量增加趋势不显著。年降水量存在准3 a、8—11 a和30 a的周期,以准11 a周期最为突出。降水量变化以春季增长趋势最显著,可在干旱季补充土壤水分,减轻风沙化土地的发生发展。秋季和冬季增长趋势不明显,夏季降水量呈减小趋势。就季节降水变化的时间尺度和周期性而言,2007年后四季降水表现为,春季在20—30 a时间尺度上将处于偏高期,夏季在8—12 a时间尺度上将处于偏低期,秋季在8—12 a时间尺度上将处于偏低期,冬季在20—30 a时间尺度上将出现向降水偏高的过渡期。

Based on daily precipitation data of four weather stations from 1957 to 2007 in the middle reaches of Yarlung Zangbo River, the characteristics of precipitation and its cycle were analyzed at different time scales by climate tendency rate and wavelet analysis. The results show that the minimum precipitation occurs in 1980s. Mean annual precipitation from 2000 to 2007 is roughly equal to that in 1990s or 1960s. Inter-decadal and annual variations of precipitation are similar in summer and autumn. Annual precipitation increases from 1957 to 2007, while it is not significant. Annual precipitation cycles are obvious with 3 years, 8-11 years and 30 years, especially 11 years. The increasing trend of precipitation is the most obvious in spring, while it is not significant in autumn and winter. Precipitation takes on the decreasing trend in summer. Spring precipitation could supply soil water during drought and prevent desertificated land spread. For time scales and cycles of seasonal precipitation, precipitation will be high in spring at 20-30 years time scale and low in summer and autumn at 8-12 years time scale after 2007. Winter will become transition period of precipitation amount from the low to the high at 20-30 years time scale.