Application of radiometric temperature observations for energy balance estimation over agricultural sites in the Little Washita during SGP99 Experiment

During the The Southern Great Plains 1999 (SGP99) Hydrology Experiment, radiometric temperature and surface energy balance data were collected over 4 fields in the Little Washita Watershed which comprise the major land cover types for this region. The radiometric temperature observations together with local screen level air temperature measurements are used with "single-source" approaches for computing sensible heat flux. The results suggest that single-source approaches require site specific calibrations. In addition, for regional applications with satellite data, this approach is particularly sensitive to uncertainty in specifying air temperature for each pixel. An alternative "two-source" approach, which considers soil and vegetation contribution to the radiometric temperature observation and turbulent heat fluxes is described. When used in a time difference scheme with temporal trace in radiometric and air temperature observations, it is shown to be significantly less sensitive to uncertainty in these observations compared to approaches which use absolute radiometric-air temperature differences.