基于TRMM数据的拉萨河流域降水时空分布规律研究

摘要

以拉萨河流域为研究区,通过与流域内地面站点降水数据的对比研究,在月和年尺度上评估了热带降雨观测计划(TRMM)降水数据的精度,并研究了拉萨河流域降水时空分布规律.结果表明,在月尺度上,TRMM降水量与站点实测降水量相关系数R2为0.96,平均绝对偏差MAE为7.1 mm,纳什效率系数NSE为0.93;在年尺度上,两者的相关系数R2为0.86,平均绝对偏差MAE为57.1 mm.总体上说,卫星降水数据与地面降水数据在拉萨河流域具有良好的一致性,较高的精度和可信度.在降水空间分布上,拉萨河流域整体呈现由东南向西北递减的趋势;在降水时间分布上,大部分降水集中在6～9月,最大值在7、8月,两月总降水量为303.1 mm,占全年降水的50.4％,11月至次年3月很少有降水发生,最小值在12月,为1.8 mm,仅占全年降水的0.3％.%This paper evaluates the accuracy of Tropical Rainfall Measurement Mission(TRMM) precipitation data on both monthly and annual scale by contrasting with observations from the meteorological stations located in the Lhasa River Basin.The results show that TRMM has strong correlation and high reliability with the observed precipitation on the monthly scale;the correlation coefficient between this two sets of data is 0.96;the mean absolute error is 7.1mm;and the Nash efficiency coefficient is 0.93;on the annual scale, the correlation coefficient is 0.86 and the mean absolute error is 57.1mm.On the basis of the evaluation, an attempt has been made to study the temporospatial distribution of precipitation in this area with TRMM precipitation data.There is a decreasing trend from southeast to northwest.Precipitation amount in July and August is 303.1mm, accounted for 50.4％ of the annual precipitation;and most of precipitations concentrate in June to September.Precipitation hardly occurs during November to March the following year;the valley value appearing in December is 1.8 mm, accounted for 0.3％ of the annual precipitation.