Evaluation of Global Daily Reference ET Using Oklahoma’s Environmental Monitoring Network—MESONET

The objective of this study is to evaluate the potential utility of the USGS Global Data Assimilation System (GDAS) 1-degree, daily reference Evapotranspiration (ET<Subscript>0</Subscript>) products by comparing them with observed Oklahoma mesonet daily ET<Subscript>0</Subscript> over a 2 year period (2005–2006). The comparison showed a close match between the two independent ET<Subscript>0</Subscript> products, with bias within a range of 10% for most of the sites and the overall bias of − 2.80%. The temporal patterns are strongly correlated, with a correlation coefficient above 0.9 for all groups. In summary, we conclude that (1) the consistent low bias shows the original GDAS ET<Subscript>0</Subscript> products have high potentials to be used in land surface modeling; (2) the high temporal correlations demonstrate the capability of GDAS ET<Subscript>0</Subscript> to represent the major atmospheric processes that control the daily variation of surface hydrology; (3) The temporal and spatial correspondences in trend between independent datasets (GDAS and MESONET) were good. The finding in Oklahoma, a different hydro-climate region from a similar regional study conducted in California by Senay et al. (J Am Water Res Assoc 44(4):969–979, <CitationRef CitationID="CR18">2008</CitationRef>), reconfirms the reliability and potential of using GDAS reference ET for regional energy balance and water resources management in many parts of the world. Copyright Springer Science+Business Media B.V. 2011