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Upscaling and Downscaling—A Regional View of the Soil–Plant–Atmosphere Continuum

^a Dep. of Soil Sci., Univ. of Wisconsin, Madison, WI 53706
^b USDA-ARS, Hydrology and Remote Sensing Lab., Bldg. 007, BARC West, Beltsville, MD 20705

View larger version (92K): [in a new window]   Fig. 1. The genealogy of the ALEX multiscale modeling suite.

View larger version (51K): [in a new window]   Fig. 2. Schematic descriptions of (a) the ALEX model of sensible and latent heating and C assimilation fluxes, (b) the remote sensing two-source model (TSM), (c) the regional-scale ALEXI model, and (d) disaggregated ALEXI (DisALEXI) model. ABL, atmospheric boundary layer.

View larger version (37K): [in a new window]   Fig. 3. Comparison of daily integrated measurements of net radiation (RN), soil heat flux (G), sensible heat (H), and latent heat (LE) made in six vegetative stands with estimates generated by the ALEX model. The root mean square difference (RMSD) between measurements and model estimates for all fluxes combined is 0.9 MJ day-1 (15% of the mean observed flux), with a coefficient of determination (R2) of 0.97 (Anderson et al., 2000).

View larger version (105K): [in a new window]   Fig. 4. (a) Six-day composite of system (soil + canopy) potential evapotranspiration (ET) ratio estimates from the ALEXI model at 5-km resolution, ending 1 July 2002. The nominal time associated with this image is 1.5 h before local noon, the time of the second GOES image used to compute surface radiometric temperature change. (b) Six-day accumulated precipitation, based on the National Centers for Environmental Prediction (NCEP) daily precipitation analysis product. (c) Canopy potential ET ratio. (d) Soil potential ET ratio.

View larger version (37K): [in a new window]   Fig. 5. Comparison of instantaneous measurements (1.5 h before local noon) of net radiation (RN), soil heat flux (G), sensible heat (H), and latent heat (LE) made in four vegetative stands with estimates generated by the ALEXI model using local, ground-based inputs. The root mean square difference (RMSD) between measurements and model estimates for all flux components is 54 W m-2 (19% of the mean observed flux), with a coefficient of determination (R2) of 0.95.

View larger version (102K): [in a new window]   Fig. 6. Maps at 24-m resolution of (a) surface radiometric temperature (TR) and (b) disaggregated latent heat flux estimates (LE) over an experimental study area near El Reno, OK, for 2 July 1997 (Norman et al., 2003). Stars on the radiometric temperature map indicate the locations where the measurements shown in Fig. 7 were acquired.

View larger version (24K): [in a new window]   Fig. 7. Comparison of instantaneous measurements (1.5 h before local noon) of net radiation (RN), soil heat flux (G), sensible heat (H), and latent heat (LE) made in four sites of varying leaf area index (LAI) with 30-m flux estimates disaggregated using the DisALEXI technique. The root mean square difference (RMSD) between measurements and model estimates for all flux components is 38 W m-2 (12% of the mean observed flux), with a coefficient of determination (R2) of 0.98 (Norman et al., 2003).

View larger version (88K): [in a new window]   Fig. 8. Spatial fields of Bowen ratio values computed by the TSM-LES (ßLES) and the TSM with uniform upper boundary conditions at 10 m (ßEQ2) for three cases where the variance () in the input surface temperature field was unchanged (1x) and increased by 2x and 3x.