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Publication #CIR 1515

Field Observations During the Sixth Microwave Water and Energy Balance Experiment (MicroWEX-6): from June 19 through November 30, 20061

Fei Yan, Hwan Hee Han, Ruofan Yang, Joaquin Casanova, Jasmeet Judge, Jennifer Jacobs, Orlando Lanni, and Larry Miller2

Abstract—Circular1515

Full text of this document is available at http://edis.ifas.ufl.edu/pdffiles/AE/AE40900.pdf

For accurate prediction of weather and near-term climate, root-zone soil moisture is one of the most crucial components driving the surface hydrological processes. Soil moisture in the top meter is also very important because it governs moisture and energy fluxes at the land-atmosphere interface and it plays a significant role in partitioning of the precipitation into runoff and infiltration.

Energy and moisture fluxes at the land surface can be estimated by Soil-Vegetation-Atmosphere-Transfer (SVAT) models. These models are typically used in conjunction with climate prediction models and hydrological models. Even though the biophysics of moisture and energy transport is well-captured in most current SVAT models, the computational errors accumulate over time and the model estimates of soil moisture diverge from reality. One promising way to significantly improve model estimates of soil moisture is by assimilating remotely sensed data that is sensitive to soil moisture, for example microwave brightness temperatures, and updating the model state variables.

The microwave brightness at low frequencies (< 10 GHz) is very sensitive to soil moisture in the top few centimeters in most vegetated surfaces. Many studies have been conducted in agricultural areas such as bare soil, grass, soybean, wheat, pasture, and corn to understand the relationship between soil moisture and microwave remote sensing. Most of these experiments conducted in agricultural regions have been short-term experiments that captured only a part of growing seasons. It is important to know how microwave brightness signature varies with soil moisture, evapotranspiration (ET), and biomass in a dynamic agricultural canopy with a significant biomass (4-6 kg/m2) throughout the growing season.

The goal of MicroWEX-6 was to understand the land-atmosphere interactions during the growing season of cotton, and their effect on observed microwave brightness signatures at 6.7 GHz and 1.4 GHz, matching that of the satellite based microwave radiometers, AMSR, and the SMOS mission, respectively. Specific objectives of MicroWEX-6 are:

  1. To collect passive microwave and other ancillary data to develop and calibrate a dynamic microwave brightness model for cotton.

  2. To collect energy and moisture flux data at land surface and in soil to develop and calibrate a dynamic SVAT model for cotton.

  3. To evaluate feasibility of soil moisture retrievals using passive microwave data at 6.7 and 1.4 GHz for the growing cotton canopy.

Related publications can be found on the Microwave Water and Energy Balance Experiments topic page:

http://edis.ifas.ufl.edu/TOPIC_Microwave_Water_and_Energy_Balance_Experiments

Footnotes

1.

This document is CIR 1515, one of a series of the Department of Agricultural and Biological Engineering, UF/IFAS Extension. Original publication date May 2007. Reviewed January 2017. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Fei Yan; Hwan Hee Han, Civil Engineering Department, University of New Hampshire; Ruofan Yang; Joaquin Casanova, graduate research assistant; Jasmeet Judge, associate professor and director of Center for Remote Sensing of UF; Jennifer Jacobs, associate professor, Civil Engineering Department, University of New Hampshire; Orlando Lanni, former engineer; and Larry Miller, engineer; Department of Agricultural and Biological Engineering, UF/IFAS Extension, Gainesville, FL 32611.


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U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.