Location: Soil and Water Management ResearchTitle: Operational evapotranspiration mapping using remote sensing and weather datasets: A new parameterization for the SSEB approach Author
Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2012
Publication Date: 6/1/2013
Citation: Senay, G.B., Bohms, S., Singh, R.K., Gowda, P., Velpuri, N., Alemu, H., Verdin, J.P. 2013. Operational evapotranspiration mapping using remote sensing and weather datasets: A new parameterization for the SSEB approach. Journal of the American Water Resources Association. 49(3):577-591. Interpretive Summary: Simplified Surface Energy Balance (SSEB) model is one of the most simplified approaches available for mapping evapotranspiration (ET) at a regional scale. However, SSEB requires manual selection of hot and cold pixels for estimating daily ET. In this study, the SSEB is revised to eliminate the step that involves manual selection of hot and cold pixels and evaluated. Performance of the revised SSEB approach indicated that the revised SSEB has the potential for use in operational applications at continental scales.
Technical Abstract: The increasing availability of multi-scale remotely sensed data and global weather datasets is allowing the estimation of evapotranspiration (ET) at multiple scales. We present a simple but robust method that uses remotely sensed thermal data and model-assimilated weather fields to produce ET for the contiguous US (CONUS) at monthly and seasonal time scales. The method is based on the Simplified Surface Energy Balance (SSEB) approach which is now parameterized for operational applications, renamed as SSEBop. The innovative aspect of the SSEBop parameterization is that it uses pre-defined, boundary conditions that are unique to each pixel for the "hot" and "cold" reference conditions. The SSEBop model was used for computing ET for 12 years (2000-2011) using the MODIS and Global Data Assimilation System (GDAS) data streams. SSEPop ET results compared reasonably well with monthly eddy covariance ET data (explaining 64% of the observed variability across diverse ecosystems in the contiguous US) during 2005. Twelve annual ET anomalies (2000-2011) depicted the spatial extent and severity of the commonly known drought years in CONUS. More research is required to improve the representation of the pre-defined boundary conditions in complex terrain at small spatial scales. SSEBop model was found to be a promising approach to conduct water use and availability studies in CONUS, with a similar opportunity in other parts of the world. The approach can also be applied with other thermal sensors such as Landsat.