Submitted to: International Geoscience and Remote Sensing Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 25, 2001
Publication Date: N/A
Interpretive Summary: The ability to use remotely sensed surface temperature data to estimate the evaporation from the land is a very useful techniques for managing water use from cropped surface. This paper describes a method for doing this using satellite based surface temperature observations.
The recent availability of multi-band thermal infrared imagery from the Advanced Spaceborne Thermal Emission & Reflection radiometer (ASTER) on NASA's Terra satellite has made feasible the estimation of evapotranspiration at 90 meter resolution. One critical variable in evapotranspiration models is surface temperature. With ASTER the temperature can be reliably determined over a wide range of vegetative conditions. When ASTER data are combined with meteorological observations, surface temperatures accurate within 1-2 C can be obtained. ASTER-based evapotranspiration estimates for a few days during 2000 were made over two different regions: sub-humid grazing and wheat lands in central Oklahoma and semi-arid rangeland in southern New Mexico. Daily evapotranspiration was estimated by applying instantaneous ASTER surface temperatures, as well as ASTER-based vegetation indices from visible-near infrared bands, to a two-source energy flux model and combining the result with separately acquired hourly solar radiation data. The estimates of surface fluxes show reasonable agreement (50-100W/m^2) with ground-based eddy-correlation measurements and illustrate how ASTER measurements can be applied to heterogeneous terrain. There are some discrepancies, however, and these may in part be due to difficulty quantifying fractional cover of senescent vegetation.