Evaluating the Semiempirical H - Q Model Used to Calculate the L-Band Emissivity of a Rough Bare Soil

In this paper, a numerical modeling approach was used to evaluate the semiempirical H-Q model used in the Soil Moisture and Ocean Salinity (SMOS) retrieval algorithm to account for roughness effects over bare soil. The H-Q model uses four parameters, H R , Q R , N RH , and N RV , which are usually c...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2013-07, Vol.51 (7), p.4075-4084
Main Authors: Lawrence, H., Wigneron, J-P, Demontoux, F., Mialon, A., Kerr, Y. H.
Format: Article
Language:English
Subjects:
Applied geophysics
Correlation
Earth sciences
Earth, ocean, space
Exact sciences and technology
Finite element methods
Internal geophysics
Modeling
Numerical models
passive microwave remote sensing
Rough surfaces
Soil moisture
soil moisture retrievals
Surface roughness
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Summary:In this paper, a numerical modeling approach was used to evaluate the semiempirical H-Q model used in the Soil Moisture and Ocean Salinity (SMOS) retrieval algorithm to account for roughness effects over bare soil. The H-Q model uses four parameters, H R , Q R , N RH , and N RV , which are usually calibrated at the ground scale for different surface types. The aim of this paper is to investigate whether these empirical parameters could be linked to the physical roughness parameters of standard deviation of surface heights σ and autocorrelation length L c . First, a numerical modeling approach was used to calculate rough soil emissivities for different roughness and soil moisture conditions. Second, H -Q model parameters were retrieved by minimizing a cost function between these emissivities and those calculated by the H -Q model. It was found that the retrieved H R could be related directly to Zs = σ 2 /L c and that Q R , N RV , and N RH were dependent on H R . H R was found to have a negligible dependence on soil moisture. Based on these results, a new model was proposed where the four H-Q model parameters were calibrated to Zs. This model was tested on the PORTOS 1993 data set and found to yield a root-mean-square difference between the retrieved and measured soil moisture values of ~ 0.03 m 3 /m 3 , which was within the desired 0.04-m 3 /m 3 error margin for the SMOS mission.
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2012.2226995