Project Number: 6209-13000-013-11
Project Type: Specific Cooperative Agreement

Start Date: Jun 01, 2007
End Date: May 31, 2010

Objective:
1. Evaluate METRIC and the Two Source Model for their ability to estimate ET at point, plot, field and regional scales; 2. Evaluate the effects of remote sensing pixel resolution (thermal band) on modeled energy balance components of irrigated and dryland cropping systems, and rangeland systems; and 3. Develop and evaluate algorithms to improve spatial resolution of surface temperature data derived from Aircarft/Landsat/MODIS thermal images using high resolution visible, NIR and SWIR images for the semi-arid, highly advective Texas High Plains Region. AMENDMENT 2 OBJECTIVES: 4. Collaborate with University of Alabama (UA) in comparing their aircraft-based flux segmentation method with surface spatial fluxes derived from the aircraft imagery, integrated with appropriate footprint functions. 5. Work with the USDA-ARS-HRSL and USDA-ARS-CPRL groups in obtaining spatially distributed biophysical parameters (LAI, fractional cover, land use, etc.) from remote sensing and in validating surface fluxes from the ALEXI/DisALEXI methodology and other flux models that will be applied at regional scales.

Approach:
The proposed study concentrates on the region in and around the Conservation and Production Research Laboratory (CPRL), USDA-ARS at Bushland, TX. Objective 1: ET maps will be derived for the study area by applying METRIC¿ and TSEB models to aircraft (acquired at 1 m), TM, and MODIS data. Detailed methodology provided in Allen et al. (2007a, b) for the METRICTM model and in Kustas and Norman (1996) for the TSEB model will be used in this study. The capability of the remote sensing methodology to estimate instantaneous, daily and seasonal ET will be assessed. In the case of instantaneous ET estimation, ET reports from 4 lysimeters and 3 scintillometers will be used for model evaluation. The daily and seasonal evaluations will use the lysimeter and scintillometer daily and seasonal cumulative (sums) of 30-min ET, respectively. Objective 2: ET and other surface flux maps (G, H, and Rn) derived from aerial, TM, and MODIS datasets represent the spatial ET pattern at successive increasing scales. To understand the role of landscape heterogeneity and its influence on the scaling behavior of ET and other surface fluxes, similarity between the maps derived from different sensors will be tested. This will be done by comparing and contrasting the histograms of the flux variations and resulting statistics for different sensors (for different spatial resolutions). Objective 3: The downscaling of thermal images from aircraft, Landsat Thematic Mapper (TM) and MODIS sensors will be explored by relating low-resolution surface temperature pixels with associated high-resolution surface reflectance and vegetation indices derived from visible, NIR and SWIR images acquired on the same sensor. Areas ranging from low to high surface temperature by vegetation type will be selected for this purpose. Objective 4 (Amendment 2): Acquire and process additional high-resolution multispectral and thermal infrared imagery in support of the UA flux aircraft flights during BEAREX08 (Bushland Evapotranspiration and Agricultural Remote Sensing EXperiment 2008). Derive from various modeling approaches, surface flux maps to compare with the UA aircraft-based segmented fluxes for BEAREX08. This will necessitate investigating the utility of flux-footprint algorithms, particularly for the higher altitude aircraft-based flux observations. Objective 5 (Amendment 2): Model output from ALEXI/DisALEXI methodology and other remote sensing-based surface energy balance models will be applied to the satellite and aircraft imagery by USDA-ARS-HRSL and USDA-ARS-CPRL groups as well as models under development by the USU group. A model inter-comparison will be conducted as well as validation using the tower and aircraft-based flux observations collected during BEAREX08.