2000-2014年天山山区蒸散发时空动态特征

Spatiotemporal Dynamic Change Characteristics of Evapotranspiration in Tianshan Mountains from 2000 to 2014

利用MODIS ET数据集中2000—2014年的地表实际蒸散发量产品,运用变异系数、Theil-Sen median趋势分析与Mann-Kendall检验和Hurst指数法,探讨了中国天山山区蒸散发的空间格局、空间异质性和时间变化特征及未来趋势预测。研究表明:(1)2000—2014年天山山区蒸散发量总体较高,蒸散发量大于400mm的区域占总面积的49.172%。受降水量控制,ET在空间上有西部大东部小、北部大南部小的特点;受土地覆盖的影响,ET的高值区(>400mm)主要为山区的林地和草地,而低值区(<200mm)主要为稀疏植被区,不同土地覆盖的ET大小为:农用地>林地>草地>稀疏植被。(2)近15a全区蒸散发变异程度不明显,以相对较低的波动变化为主,面积比例为45.140%,其中高波动变化的区域是受土地覆盖演变的影响。(3)15a间全区年均蒸散发量大致分布在305~387mm,呈波动变化,总体有减小趋势,变化率为-2.911 6mm/a。基于像元尺度的分析也表明全区ET以减小的变化趋势为主,面积比例为83.022%。天山山区蒸散发量的减小趋势,是区域降水量减少所致。(4)全区ET的Hurst指数均值为0.747,Hurst指数大于0.5的范围所占比例为86.382%。未来全区蒸散发的变化趋势以持续性减小为主,面积比例为69.888%,其中15.589%区域的变化趋势无法确定。

Using MODIS ET data of actual surface evapotranspiration products that were concentrated from 2000 to 2014, we used variable coefficients, the Theil-Sen median trend analysis, Mann-Kendall test, and H urst index, to investigate the spatial pattern of evapotranspiration, spatial heterogeneity, characteristics of time variation, and future trends considering the Tianshan Mountains. The results showed as the following. （1） Evapotranspiration over the entire region was very high from 2000 to 2014, and the area with evapotranspi- ration greater than 400 mm accounts for 49. 172~//00 of the total area. Affected by precipitation, evapotranspiration is high in the west and north, but low in the east and south. Affected by land cover types, areas with higher value of evapotranspiration （more than 400 mm） mainly included the mountain forestland and grassland, but the area with low value of evapotranspiration （less than 200 mm） concentrated in sparse vegetation region. Evapotranspiration data decreased in the order： cropland^forestland~〉grassland^sparse vegetation. （2） The degree of variation in evapo- transpiration over the past 15 years for the entire region is not obvious, but shows a slight fluctuation. The proportion of areas with slight fluctuations accounts for 45. 140% of the total area. Among them, the region of high fluctuation was caused by the change of land cover types. （3） The value of evapotranspiration over the past 15 years for the entire region varied from 305 mm to 387 mm and shows changes in the fluctuations with a weakly decreasing trend with the change rate of -2. 911 6 mm/year. An analysis based on the pixel scale also shows a mainly decreasing trend, the area with decrease trend accounts for 83. 022% of the total area. This decrease trend of regional evapotranspiration was caused by the decrease of precipitation. （4） The Hurst index average of evapotranspiration for the entire region is 0. 747. The area with Hurst index greater than 0.5 accounts for 86. 382% of the total area. The change trend of evapotranspiration in the future for the entire region is mainly towards a persistent decrease and this area accounts for 69. 888% of the total area. However, the trend of changes for 15. 589% of the area cannot he determined.