%0 Journal Article
%T A New Evapotranspiration Model Accounting for Advection and Its Validation during SMEX02
%A Yongmin Yang
%A Hongbo Su
%A Renhua Zhang
%A Jianjun Wu
%A Jianwei Qi
%J Advances in Meteorology
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/389568
%X Based on the crop water stress index (CWSI) concept, a new model was proposed to account for advection to estimate evapotranspiration. Both local scale evaluation with sites observations and regional scale evaluation with a remote dataset from Landsat 7 ETM+ were carried out to assess the performance of this model. Local scale evaluation indicates that this newly developed model can effectively characterize the daily variations of evapotranspiration and the predicted results show good agreement with the site observations. For all the 6 corn sites, the coefficient of determination ( ) is 0.90 and the root mean square difference (RMSD) is 58.52W/m2. For all the 6 soybean sites, the and RMSD are 0.85 and 49.46W/m2, respectively. Regional scale evaluation shows that the model can capture the spatial variations of evapotranspiration at the Landsat-based scale. Clear spatial patterns were observed at the Landsat-based scale and are closely related to the dominant land covers, corn and soybean. Furthermore, the surface resistance derived from instantaneous CWSI was applied to the Penman-Monteith equation to estimate daily evapotranspiration. Overall, results indicate that this newly developed model is capable of estimating reliable surface heat fluxes using remotely sensed data. 1. Introduction Evapotranspiration ( ) is a very important process which relates to energy and water exchange between the hydrosphere, atmosphere, and biosphere [1, 2]. The research on evapotranspiration is very crucial to further our understanding of global climate change, land-atmosphere interaction, water cycle, and ecological studies [3¨C5]. Recently, the ˇ°evaporation paradox,ˇ± which is referred to as the decreasing pan observations and the increasing surface air temperature over the past 50 years, has been reported in many regions around the world [6¨C8]. Pan evaporation provides a measurement of the integrated effect of radiation, wind, temperature, and humidity on the evaporation from an open water surface. Actual evaporation is the quantity of water that is actually removed from natural surfaces. There is a need to understand the change of actual evapotranspiration at regional and global scales behind evaporation paradox. Actual evapotranspiration is a key factor to understand the regional water cycle and energy balance. An in-depth understanding of regional evapotranspiration will benefit the water resource planning and management in arid and semiarid areas [9]. As a promising means of land surface observation, remote sensing has some salient characteristics, such as large scale
%U http://www.hindawi.com/journals/amete/2013/389568/