An empirical approach to retrieving monthly evapotranspiration over Amazonia
Abstract:The extent of evapotranspiration (E T) over the Brazilian Amazon rainforest remains uncertain because in situ measurement sites do not cover the entire domain, and the fetch of these sites is only of the order of 103 m. In this investigation we developed an empirical method to estimate E T over the Brazilian Legal Amazon (BLA). The work was based on an improved physical understanding of what controls E T over the Amazonia rainforest resulting from analyses of recent in situ observations. Satellite data used in this study include the Enhanced Vegetation Index (EVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the surface radiation budget from the International Satellite Cloud Climatology Project (ISCCP). The empirical model was validated by measurements performed at four upland forest sites. The observed values and the calculated modelled values at these sites had the same mean and variance. On a seasonal scale, regional modelled E T peaks during the austral spring (September to November), as reported in the literature. In addition, the empirical model allows us to estimate the regional seasonal and interannual distributions of E T/precipitation rates.
Document Type: Research Article
Affiliations: 1: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA 2: Earth System Science and Ecology and Evolutionary Biology, University of California, Irvine, CA, USA 3: Department of Geography, Boston University, Boston, MA, USA 4: Department of Geography, University of Georgia, Athens, GA, USA
Publication date: 2008-12-01