Estimating Evapotranspiration Using Improved Fractional Vegetation Cover and Land Surface Temperature Space

基于改进的地表温度-植被覆盖特征空间估算地表蒸散(英文)

Vegetation index-land surface temperature （VI-T s ） space has been widely used to estimate evapotranspiration and soil moisture. The limitation of this method is the uncertainty of the observed dry edge, which is usually fitted by scatter plots. Here, a method was used to locate true dry and wet edges based on energy balance formulation, and a simple method to estimate surface energy flux is proposed based on the improved Fractional vegetation cover-Land surface temperature （F v -T s ） space. Seventeen days of MODIS products were selected to estimate evapotranspiration and the estimated sensible heat flux （H） is compared with Large Aperture Scintillometer （LAS） data at a site in Zhengzhou, resulting in a RMSE of 44.06 W m^-2 , bias of 36.99 W m^-2 and R^2 of 0.71. The H scatter plots of estimation versus observation show clearly that most points are around the 1：1 line. Overall, the located true and wet edges are more accurate than the observed true edge. Our results can also be applied to improve the estimation of soil moisture.

地表温度-植被指数特征空间被广泛应用与地表蒸散估算和土壤湿度监测,而利用散点图直接拟合干边会造成很大的不确定性。本研究采用改进的地表温度-植被覆盖特征空间进行地表通量的计算。该方法是基于能量平衡公式进行干边定位,从而减少干边确定过程中的不确定性。我们选取的17天的MODIS数据以及相应气象数据进行地表蒸散计算,并采用郑州的LAS观测站验证显热通量计算值,估算结果均方根误差(RMSE)、偏差(Bias)和相关系数平方(R2)分别为44.06Wm-2、36.99Wm-2和0.71。总体来讲,通过能量平衡公式确定的理论干边相比通过散点图拟合的实测干边更合理。