基于MOD16的北洛河流域蒸散发空间格局演变研究

目的]探究北洛河流域地表实际蒸散发年际和年内的时空变化特征,为该区域的生态基准与生态需水量研究、退耕还林效果研究提供理论依据。方法]基于北洛河流域2000—2014年MOD16遥感数据、气象数据、水文数据和2011年土地利用数据,采用流域水量平衡法、均值法、标准差法和线性趋势法进行蒸散发(ET)时空变化特征分析。结果]流域年蒸散量在波动中缓慢上升,波动范围为395.4~517.4mm/a,15aET均值为446.74mm/a,年内蒸散量呈单峰型分布,季节性变化特征明显,地表蒸散主要集中在5—9月,最高值出现在8月;经与北洛河流域的实测降水空间插值结果比较,MOD16-ET估算结果的相对误差均值为12.04%,相关系数达到0.81;流域内上游至下游的ET剖面线波动明显,呈不规则的"波动曲线"形态;流域内ET值年际变化空间分布特征明显,中游和上游地区以增加趋势为主,下游以减少趋势为主。结论]近15a来北洛河流域蒸散发整体呈现增大趋势,主要驱动因素为人类活动,尤其是退耕还林和水土保持等工程的实施。

Analysis of Spatial and Temporal Variation of EvapotranspriationBased on MOD16 in Beiluo River Basin

Objective] The objective of this paper is to explore the spatial and temporal characteristics of evapotranspriation(ET) in the Beiluo River basin,and provide theoretical basis for the study of ecological benchmark and ecological water requirement and the effect of returning farmland to forest.Methods] Based on MOD16 remote sensing image data,meteorological and hydrological date during 2000-2014,and the land use date in 2011,we used river basin water balance method,method of mean value,the standard deviation method and the linear trend method to analysis the spatial and temporal variation characteristics of evaporation.Results] The mean annual evapotranspiration of Beiluo River basin increased slowly with values ranged from 395.4 to 517.4 mm,and average evapotranspiration during the past 15 years was 446.74 mm.The monthly variation of evapotranspiration within the year show a unimodal pattern,it was mainly concentrated in the period from May to September,and its peak value occurred in August.The average relative error was 12.04％ between spatial interpolation results based on measured rainfall and estimates based on MOD16-ET,the correlation coefficient was 0.81.The profile line of ET changed greatly from upstream to downstream of the Beiluo River basin,which presented the irregular "wave curves".The spatial variation of annual ET was obvious in the basin.The ET showed an increasing trend in the midstream and upstream,while it showed a decreasing trend in the downstream.Conclusion] In the recent 15 years,the evapotranspiration in Beiluo River basin showed an increasing trend,and human activity was the main driving force,especially the implementation of grain for green project and soil and water conservation project.