The Atmosphere-Land Exchange Inverse (ALEXI) model estimates surface fluxes of heat and water vapor on the 5-10km scale using primarily satellite-derived input data, including surface radiometric temperature, downwelling short- and long-wave radiation, and vegetation indices.

Using ALEXI, surface fluxes and flux climatologies are being evaluated over several modeling domains on a daily basis. These domains currently include the 48 contiguous United States, and the IHOP and SMEX02 field experiment sites.

Direct validation of 5-10km model flux estimates is a difficult task, as measurements on comparable scales are costly to obtain. Comparisons with aircraft fluxes acquired during SMEX02 are underway. In addition, daily comparisons are being made with observations from tall towers in the AmeriFlux network, and with maps of antecedent precipitation.

Flux disaggregation provides an indirect method for validating largescale flux estimates. The DisALEXI algorithm uses high resolution surface temperature and vegetation cover information to disaggregate 5km ALEXI predictions down to the 30-100m scale for direct comparison with ground-based measurements.

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