Applications of the ALEXI soil moisture model and highlights of current projects

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Monday, 18 January 2010
John Mecikalski, Univ. of Alabama, Huntsville, AL; and C. R. Hain and L. A. Schultz

The Atmosphere-Land Exchange Inverse (ALEXI) model was developed as an

auxiliary means for estimating surface fluxes over large regions primarily using remote-sensing data. The model is unique in that no information regarding antecedent precipitation or moisture storage capacity is required - the surface moisture status is deduced from a radiometric temperature change signal. ALEXI uses the available water fraction (fAW) as a proxy for soil moisture conditions. Combining fAW with ALEXI's ability to provide valuable information about the partitioning of the surface energy budget, which can dictated largely by soil moisture conditions, accommodates the retrieval of an average fAW from the surface to the rooting depth of the active vegetation.

Using this approach has many advantages over traditional energy flux and soil moisture measurements (towers with limited range and large monetary/personnel costs) or approximation methods (parameterizations of the relationship between available water and soil moisture) in that data is available both spatially and temporal over a large, non-homogenous, sometimes densely vegetated area. Being satellite based, the model can be run anywhere thermal infrared satellite information is available.

The current ALEXI climatology dates back to March 2000 and covers the continental U.S. Examples of projects underway using the ALEXI soil moisture retrieval tools include the Southern Florida Water Management Pro ject; NASA's Project Nile, which proposes to acquire hydrological information for the water management in the Nile River basin; and a USDA project to expand the ALEXI framework to include Europe and parts of northern Africa using data from the European geostationary satellites, specifically the Meteosat Second Generation (MSG) Series.