基于地面观测的遥感监测蒸散量验证方法研究

为了保证遥感监测蒸散量的准确性,需建立一套较完整的遥感监测蒸散量地面验证方法对其进行验证.通过由大孔径闪烁仪、涡动相关仪和自动气象站等组成的蒸散量观测系统可以获取不同卫星像元尺度蒸散量的地面观测值.自2002年以来,由海河流域的密云、馆陶、大兴及小汤山等站构建了一个不同卫星像元尺度蒸散量的观测站网,经过严格的观测数据处理与质量控制,获取了一大批卫星像元尺度蒸散量及其配套参数的地面观测值.同时,建立了一套基于地面观测的遥感监测蒸散量验证流程,重点对验证像元的选取以及评价指标的构建等进行探讨.依据上述验证流程,在海河流域的北京地区开展了遥感监测蒸散量的地面验证工作.利用2008年密云站和大兴站的大孔径闪烁仪观测数据,对基于MODIS数据估算的北京地区区域蒸散量进行验证.结果表明:这套基于大孔径闪烁仪观测数据的遥感监测蒸散量验证方法是合理、可行的.其中2008年北京地区遥感监测月、日蒸散量的均方差分别为13.75和0.91 mm,平均相对误差分别为22.79%、18.61%.

A Study of the Validation Method of Remotely Sensed Evapotranspiration based on Observation Data

A comprehensive validation method of remotely sensed Evapotranspiration (ET) based on observation data was proposed to ensure the accuracy of estimated ET. Thus, an observation system was equipped with a large aperture scintillometer, an eddy covariance system and an automatic weather station, and then an observation network was established at Miyun, Guantao, Daxing and Xiaotangshan sites in Hai river basin, which were set up from 2002 for ET and correlative parameters measurements at different satellite pixel scales. On this basis, rigorous data process and quality control were executed to ensure the high quality of observations. Meanwhile, a validation procedure of remotely sensed ET based on ground measurements was presented, and the method of selecting validation pixels and evaluation index were investigated intensively. According to this method, validation of remote sensing ET was performed in Beijing. Based on the LAS measurements at Miyun and Daxing sites in 2008, regional ET in Beijing area estimated by MODIS data was validated. The results demonstrated that the proposed validation method based on LAS observation data was feasible. The RMSE and MRE of estimated monthly and daily ET were 13.75、0.91 mm and 22.79%、18.61% respectively.