Accurate Calculations of Emissivities of Polar Ocean Surfaces Between 0.5 and 2 GHz Using an NIBC/Nystrom/SMCG Method

We use full-wave simulations of rough surfaces to calculate the emissivities of a polar ocean between 0.5 GHz and 2 GHz for applications in ocean salinity. High accuracy is required because the emissivity variations between flat and rough surfaces are at the order of magnitude of 10 -3 . In addition...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2020-04, Vol.58 (4), p.2732-2744
Main Authors: Du, Yanlei, Tsang, Leung
Format: Article
Language:English
Subjects:
Boundary conditions
Broadband
Computer simulation
Emissivity
Integral equations
Mathematical analysis
Method of moments
Method of moments (MoM)
neighborhood impedance boundary condition (NIBC)
Nystrom
ocean emissivity
Ocean waves
Polar environments
Rough surfaces
Roughness
Salinity
Salinity (geophysical)
Salinity effects
Sea surface
Sparse matrices
sparse matrix canonical grid (SMCG)
Surface impedance
Surface roughness
Surface water waves
Surface waves
Wavelength
Wavelengths
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Summary:We use full-wave simulations of rough surfaces to calculate the emissivities of a polar ocean between 0.5 GHz and 2 GHz for applications in ocean salinity. High accuracy is required because the emissivity variations between flat and rough surfaces are at the order of magnitude of 10 -3 . In addition, the changes of emissivity due to salinity change are only about 4.2 × 10 -4 /psu to 2.6 × 10 -3 /psu for 0.5-2 GHz over the polar region. An enhanced method is proposed by combining neighborhood impedance boundary condition (NIBC), Nystrom, and sparse matrix canonical grid (SMCG) to solve the dual surface integral equations (SIEs) using the method of moments (MoM). To simulate large-scale ocean waves using a complete ocean spectrum, the surface root-mean-square (RMS) heights are up to 22.5 cm corresponding to 1.5 times wavelength of 2 GHz. Thus, the surface lengths used are up to 333 wavelengths to account for the large RMS height. Simulation results are illustrated for 0.5-2 GHz. We show that the energy conservations are obeyed to 10 -4 . The effects of roughness and salinity on broadband polar ocean emissivity are studied with the proposed approach. Numerical simulations show that the sensitivity to salinity is still preserved in spite of roughness.
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2019.2954886