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Title: COMPARING THE UTILITY OF MICROWAVE AND THERMAL REOMOTE-SENSING CONSTRAINTS IN TWO-SOURCE ENERGY BALANCE MODELING OVER AN AGRICULTURAL LANDSCAPE

Author
item Li, Fuqin
item Kustas, William - Bill
item Anderson, Martha
item Jackson, Thomas
item BINDLISH, RAJAT - SSAI
item Prueger, John

Submitted to: Remote Sensing of Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2006
Publication Date: 5/15/2006
Citation: Li, F., Kustas, W.P., Anderson, M.C., Jackson, T.J., Bindlish, R., Prueger, J.H. 2006. Comparing the utility of microwave and thermal remote-sensing constraints in two-source energy balance modeling over an agricultural landscape. Remote Sensing of Environment. 101:315-328.

Interpretive Summary: Near-surface soil moisture and land surface temperature are very important boundary conditions in many land surface modeling schemes. In this investigation, a two-source (soil + vegetation) energy balance model using microwave-derived near-surface soil moisture as a key boundary condition (TSMSM) and another scheme using thermal-infrared (radiometric) surface temperature (TSMTH) were applied to remote sensing data collected over a corn and soybean production region in central Iowa during the Soil Moisture Atmosphere Coupling Experiment (SMACEX)/Soil Moisture Experiment of 2002 (SMEX02). Near-surface soil moisture images were from microwave imagery collected by aircraft on six days during the experiment and the land surface temperature were derived from Landsat ETM scenes. Other model inputs included Landsat derived Normalized Difference vegetation index (NDWI) and local meteorological observations as well as soil and land use classification. Six days of TSMSM output were compared with tower based flux observation, yielding a root mean square difference (RMSD) between model estimates and tower measurements of net radiation (Rn) and soil heat flux (G) of approximately 20 Wm-2, and 45 Wm-2 for sensible (H) and latent heating (LE). Similar results for H and LE were obtained at landscape/regional scales when comparing model output with transect-average aircraft flux measurements. Flux predictions from the TSMSM and TSMTH models were compared for two days when both airborne microwave-derived soil moisture and radiometric surface temperature (TR) data from Landsat were available. These two days represented contrasting conditions of moderate crop cover/dry soil surface and dense crop cover/moist soil surface. Surface temperature diagnosed by the TSMSM was also compared directly to the remotely sensed TR fields as an additional means of model validation. The TSMSM performed well under moderate crop cover/dry soil surface conditions, but yielded larger discrepancies with observed heat fluxes and TR under the high crop cover/moist soil surface conditions. Flux predictions from the thermal-based two-source model typically showed biases of opposite sign, suggesting that an average of the flux output from both modeling schemes may improve overall accuracy in flux predictions, in effect incorporating multiple remote-sensing constraints on canopy and soil fluxes.

Technical Abstract: A two-source (soil + vegetation) energy balance model using microwave-derived near-surface soil moisture as a key boundary condition (TSMSM) and another scheme using thermal-infrared (radiometric) surface temperature (TSMTH) were applied to remote sensing data collected over a corn and soybean production region in central Iowa during the Soil Moisture Atmosphere Coupling Experiment (SMACEX)/Soil Moisture Experiment of 2002 (SMEX02). The TSMSM was run using fields of near-surface soil moisture from microwave imagery collected by aircraft on six days during the experiment, yielding a root mean square difference (RMSD) between model estimates and tower measurements of net radiation (Rn) and soil heat flux (G) of approximately 20 Wm-2, and 45 Wm-2 for sensible (H) and latent heating (LE). Similar results for H and LE were obtained at landscape/regional scales when comparing model output with transect-average aircraft flux measurements. Flux predictions from the TSMSM and TSMTH models were compared for two days when both airborne microwave-derived soil moisture and radiometric surface temperature (TR) data from Landsat were available. These two days represented contrasting conditions of moderate crop cover/dry soil surface and dense crop cover/moist soil surface. Surface temperature diagnosed by the TSMSM was also compared directly to the remotely sensed TR fields as an additional means of model validation. The TSMSM performed well under moderate crop cover/dry soil surface conditions, but yielded larger discrepancies with observed heat fluxes and TR under the high crop cover/moist soil surface conditions. Flux predictions from the thermal-based two-source model typically showed biases of opposite sign, suggesting that an average of the flux output from both modeling schemes may improve overall accuracy in flux predictions, in effect incorporating multiple remote-sensing constraints on canopy and soil fluxes.