Effects of Ocean Wind, Foam/Spray and Atmosphere on Four Stokes Parameters in Passive Polarimetric Remote Sensing of the Ocean Based on Numerical Simulations and Analytic Theory
Abstract
The research last year consisted of three parts: A. Emission, absorption and scattering by foam; B. Polarimetric passive microwave remote sensing of foam covered ocean; C. Brightness temperature of ocean with wind based on paralleled code of SMCG and PBTG. Emissvities of ocean surfaces are affected by the presence of foam. Recently, field experiments have been conducted to study the foam emissivity as a function of polarization, observation angle and frequencies between 10 GHz to 37 GHz. The measurements exhibit interesting frequency dependence. The results are not explained by simple mixing formulae nor past empirical models. In particular, the emissivities at 10 GHz are observed to be higher than or comparable to that of 37 GHz. Foam is a mixture of air bubbles and sea water. The bubbles range from sizes of hundreds of microns to millimeters. We conduct theoretical modeling based on modeling the microstructure of foam taking into account bubble size and fractional volume of water to rigorously study the emission, absorption and scattering properties and to account for the observed frequency dependence and polarimetric dependence of emissivities. In a previous paper, we used the model of air bubbles coated with a water layer. The absorption and emission are calculated by using the dense media radiative transfer theory to account for the observed emissivities. Recently, to study the effect of foam, we used Monte Carlo simulations of exact solutions of Maxwell equations. In the Monte Carlo simulations, we calculated the stochastic Green s function. We model foam as densely packed non-absorptive particles (air bubbles) in an absorptive background (sea water). Maxwell equations are put in the form of dipole interactions. Up to one or two thousand bubbles are used in the simulations. We use the Monte Carlo simulations to calculate the absorption coefficent, effective permittivity, scattering rate and phase matrix.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 2001
- Accession Number
- ADA624583
Entities
People
- Chi-te Chen
- Leung Tsang
- Lin Zhou
- Vikram Jandhyala
Organizations
- University of Washington