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Publication #CIR1492

 

Vertical Distribution of Moisture in a Growing Sweet Corn Canopy During MicroWEX-41

Joaquin Casanova, Jasmeet Judge, Mi-young Jang2

Full text of this document is available at http://edis.ifas.ufl.edu/pdffiles/AE/AE39500.pdf

Abstract

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 improve significantly 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 kgm2) throughout the growing season.

An important component in surface microwave radiative transfer is absorption of radiation by the canopy. The absorptive effect of the canopy can be characterized by the canopy optical depth, which is a function of moisture distribution, canopy dielectric properties, and frequency. This report describes the methods and measurements of the canopy moisture distribution in sweet corn during a growing season. A physically-based model for canopy optical depth can help improve model estimates of microwave brightness.

Footnotes

1.

This document is Circular 1492, one of a series of the Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published August 2006. Reviewed Janurary 2013. Please visit the EDIS website at http://edis.ifas.ufl.edu for more publications.

2.

Jasmeet Judge is an Assistant Professor and Director of Center for Remote Sensing (email: jasmeet@ufl.edu); Joaquin Casanova is an Undergraduate Research Assistant; Mi-young Jang is a Graduate Research Assistant. All authors are affiliated with the Agricultural and Biological Engineering Department, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

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