Macroscopic Foam–Spray Models for Ocean Microwave Radiometry

Abstract

We develop composition microwave electromagnetic models to calculate the emissivity of sea foam and spray. To describe foam nonuniformities, we suggest incorporating vertical profiles of an effective complex dielectric constant associated with two-phase (air-water) stratifications. We consider a certain structural hierarchy: Wet foam is modeled by mono- and polydispersed systems of bubbles; dry foam is represented by a statistical two-phase mixture containing thin water films and air; and spray is modeled by a discrete system of spherical water droplets. The impact of effective profiles on the spectral and polarization dependencies of the emissivity (signatures) is analyzed numerically using a multilayer computer-simulation technique. This technique allows us to provide a comprehensive model for variable configurations of complex effective profiles and different incidence angles. New results are generated for three basic compositions: ldquowater+foam+spray,rdquo ldquowater+spray,rdquo and ldquofoam+spray.rdquo We intend this modeling for use in advanced ocean remote sensing studies, including monitoring of gales, detection of two-phase wakes, estimations of air-sea fluxes and evaporation, and for retrieval purposes.