A Multi-Perspective Evaluation of ET variability related to recent droughts in the Southeastern United States

This study employed multiple sources of ET data to examine the spatial and temporal variability of ET over the Southeastern United states over the past fifteen years. This period corresponds to times when significant droughts developed over the region, specifically 1998-2001; 2005-06, and 2012. A composite ET data base for the period was constructed from model estimates (Penman-Monteith), satellite observations (both near IR and TIR) and eddy flux towers. The 2006 NLDC provided land coverage of the region which could be correlated with ET estimates. The Penman-Monteith method was used to compute ET for each land class present and compared to MODIS estimates and values computed by the ALEXI thermal infrared model. Satellite observations and model estimates were supported by data from 29 flux towers located around the region. Through comparisons and assimilation, a composite ET data base was constructed from these sources. The composite ET maps were compared to fluxes from a crop model (DSSAT) that is executed over the Southeastern US at a daily time step during the growing season. The data were then used to evaluate conditions associated with hydrologic and agricultural extremes (droughts) that occurred over the past fifteen years. Local and synoptic climate conditions associated with these periods which may have contributed to the ET patterns were also analyzed.