锡林河流域蒸散量时空变化遥感监测

研究选择锡林河流域为研究区，基于地表能量平衡原理，利用遥感方法对2000—2012年每年7月、2012年4—9月的MODIS影像数据进行处理，结合同期气象资料估算出流域日蒸散量，按所占日数加权得到月（旬）蒸散量。运用FAO推荐式进行了验证，平均相对误差为16.678%，在误差允许范围之内，说明该遥感方法有一定的可用性。结果表明:反演得到的蒸散量分布与地表状况比较吻合，其中低湿地植被、草甸草原蒸散量较大，锡林河流经区域的地段形成的湿地植被蒸散量较大，植被密集的地方如耕地蒸散值较大，明显高于植被稀疏的地区。在空间分布上均为上游大于中游，中游大于下游，与地表植被覆盖相一致。2000—2012年这13 a流域最大蒸散量出现在2012年，最小值出现在2000年，基本与各年7月份降水量的趋势相一致，它们之间的决定因子为0.755 3；2012年4—9月份月蒸散量和旬蒸散量随时间的变化基本为一钟形曲线，反映了植物在整个生长季的蒸散耗水状况。

Remote Sensing Monitoring of Temporal and Spatial Variation of Evapotranspiration in Xilin River Basin

The study area is located in the Xilin River basin. Remote sensing approach was used to retrieve instantaneous evapotranspiration based on the estimation of land surface fluxes by using MODIS images from July 2000 to July 2012 and from Apr. to Sept. 2012, and using auxiliary environmental data from the same periods. Daily evapotranspiration was estimated by scaling. Monthly and ten-day evapotranspiration were weighted by the number of days. Results were verified by using the FAO method. This level of uncertainty was acceptable; therefore, the method that we concluded was applicable. The result of evapotranspiration distribution was consistent with land surface conditions. The evapotranspiration of wetland vegetation and meadow grassland was higher. The evapotranspiration of dense vegetation such as farmland was higher than the sparse. With respect to the spatial distribution, the evapotranspiration in the upper reaches was always higher than in the middle and lower reaches. It was consistent with the vegetation cover. The maximum evapotranspiration of thirteen years from 2000 to 2012 appeared in 2012. The minimum value appeared in 2000. The trend of evapotranspiration was consistent with precipitation. And the determinant was 0.755 3. Changes of monthly and ten-day evapotranspiration over time showed a bell-shaped curve, which reflected water consumption of plants throughout the growing season.