Evaluation of topography effect on Evaporative Fraction from MODIS data in Taihu Basin, China

Abstract

Evaporative Fraction (EF), defined as the ratio of ET and available energy, can be estimated directly from remote sensing. Though many studies have successfully estimated EF using a contextual interpretation of radiometric surface temperature (Ts) and normalized difference vegetation index (NDVI) based on remote sensing datasets. However, little research focused on influence of topography on triangle method application in complex topographic areas. In this study, we estimate EF by triangle method with topographic correction from MODIS datasets over Taihu Basin, China, and evaluate the effects of topography on EF estimation. Our results indicate that topographic correction improves to determine quantitatively the dry and wet edges of Ts-NDVI triangle space. The value of EF was overestimated before topographic correction over mountain area. After correction, the values of EF vary in different elevation and aspect of terrain. The EF ranges from 0.2 to 0.8 with a mean of 0.5, which become more reasonable than before correction.