三江平原挠力河流域近50年降水时空分布特征

通过非参数检验法(Mann-Kendall)分析三江平原挠力河流域19个气象站点近50年(1956-2004)降水序列的变化趋势,并利用Surfer8.0做出流域降水量及倾斜度β值等值线图,研究该流域降水的时空分布特征。结果表明:时间上,总体上挠力河流域降水以年均1.500mm/a的幅度逐渐减少,其中9月份降幅最大,为-0.439mm/a;同时,夏秋两季(6～11月)降水都是减少的,特别是夏季(6～9月),降幅达-1.485mm/a;此外,流域降水年内分布不均,其中夏季降水最多,占全年降水总量的69.8%。空间上,对于年序列而言,降水大致以七星河流域为中心向下游逐渐增加,同时,龙头站附近出现了降水减少的低值中心;对于季序列而言,挠力河流域春季降水逐渐增加,最大值为0.338mm/a(八五三),而夏、秋、冬季降水逐渐减少,其中夏季降水变化较复杂,秋季降幅均值最大,冬季降幅最小。

Analysis on the spatiotemporal distribution of precipitation in the Naoli River of the Sanjiang plain during the past 50 years

On the basis of precipitation database collected from 19 meteorological stations in the Naoli River of the Sanjiang Plain during the period from 1956 to 2004,the long-term trend of precipitation in the Naoli River was analyzed by using the Mann-Kendall test,and the isopleth maps of the series of precipitation were made by Surfer 8.0,and the spatiotemporal distribution of the long-term trend of precipitation in the Naoli River was analyzed.The study results are as follows: Firstly,the mean annual precipitation was in a decrease trend and its gradient was-1.500mm/a,and the reduction gradient in September was the largest in all months,that was-0.439mm/a.In addition,the reduction was mainly caused by summer and winter,especially in summer,and its gradient was-1.485mm/a.Furthermore,the rainy season was summer and the precipitation occupied 69.8% of the annual precipitation.Secondly,spatially,the low annual precipitation occurred in the Qixing River watershed and the precipitation decreased from southwest to northeast approximately.Also,there was an obvious precipitation-decreasing center in the Longtou station.In all reasons except spring,the precipitation showed a decreasing trend all over the Naoli River watershed.Concretely,the values of precipitation in summer were both negative and positive showing the change complexity.However,the general trend in summer was deceasing.Moreover,the mean values of the gradient in fall was larger than that in winter exhibiting that contributed the most of the decreasing trend.