Mapping Evapotranspiration Coefficients in a Temperate Maritime Climate Using the METRIC Model and Landsat TM

The applicability of a land surface temperature (LST)-evapotranspiration (ET) regression model to estimate ET fraction (ETrF) was tested in the temperate maritime climate of Central Ireland. In this study, the Mapping ET at high Resolution and with Internalized Calibration (METRIC) model was applied to calculate evapotranspiration from a mixed land cover area in Central Ireland. The ETrF values estimated on a pixel-by-pixel basis using two different surface roughness maps derived from two different estimates of Leaf Area Index (LAI) showed no significant differences. The METRIC based ETrF values from a Landsat Enhanced Thematic Mapper Plus (ETM+) image from 12 July 2013 were in similar range with those obtained from a regression model using land surface temperature (LST)-ET relationship derived from a Landsat 5 Thematic Mapper (TM) image of 17 July 2006. Results indicated that ETrF values could be estimated by using LST values from Landsat TM, even when stress conditions were prevailing in the region.