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United States Department of Agriculture

Agricultural Research Service

Research Project: AIRBORNE MEASUREMENT OF LAND-SURFACE ENERGY, WATER AND CARBON FLUXES OVER HETEROGENEOUS

Location: Hydrology and Remote Sensing Laboratory

2011 Annual Report


1a.Objectives (from AD-416)
To determine spatially averaged evapotranspiration, as well as carbon and heat fluxes, between the plot and the regional scale (~20km) using a dedicated flux aircraft over irrigated agricultural region in the Texas High Plains (THS), to process and analyze the flux data using different aggregation techniques to enhance the utility of the data set for ALEXI/disALEXI model validation, scaling, and verification studies, and to provide additional flight activities and data collection to enhance the multi-disciplinary research occurrring during the intensive observation periods (i.e., providing boundary layer development data).


1b.Approach (from AD-416)
Work with UA_AERO scientist to coordinate and execute a series of airborne flux measurement campaigns. Use the resulting large-scale flux datasets to contrain/validate ALEXI model estimates and improve embedding algorithms.


3.Progress Report

The goal of this project is to work with University of Alabama (UA) scientists to coordinate and execute a series of airborne flux measurement campaigns. The resulting large-scale flux datasets will be used to constrain/validate flux estimates from the Atmosphere-Land Exchange Inverse (ALEXI) model and to improve embedded algorithms. The Bushland Evapotranspiration and Agricultural Remote Sensing Experiment, 2008 (BEAREX08) intensive field experiment was conducted during the summer months of 2008 in Bushland, Texas. An intensive aircraft campaign was developed to coordinate airborne flux measurements by UA with airborne imaging acquisitions conducted by collaborators from Utah State. Ground-based measurements of evapotranspiration (ET) were collected with eddy covariance and Bowen ratio systems and large weighing lysimeters.

The collaborating scientists at UA collected airborne flux data on multiple days during BEAREX08 over the experiment site and on transects into adjacent areas, to help in upscaling point ET measurements to field and watershed scales. The aircraft data are being processed to generate both fluxes and footprints in one-second fragments. The footprints are based on 1-D footprint model and will be used to bound the landscape over which the footprint was generated. These footprints can be used to describe and constrain the scale and land use types of comparisons to fixed tower-based and remotely sensed flux estimates. These fragments (and associated footprints) will then be collated into different contiguous and noncontiguous (land classification based) flux transects. Statistical distributions of flux estimates from these constructed flux transects will be generated using a bootstrap method will allow spatial uncertainty to be associated with each flux estimate. Uncertainty estimates will markedly improve the use aircraft-based fluxes for multiple method comparisons, model parameterization, and model validation. Spatially averaged fluxes along a flight transect are being compared to modeled and gridded fluxes based on data from the airborne images and calibrating data from flux towers.

The ADODR has monitored the progress of this project through email correspondence, conference calls and periodic meetings with the University of Alabama scientists.


Last Modified: 4/20/2014
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