We are developing the following problems: a) combine optical and microwave technic to the indication of non-linear surface waves and wave breaking field; b) modelling of microwave propagation in a multiphase air-water interface; c) obtain quantitative dependencies of microwave radiation on geometry and statistics of wave breaking field in ocean surface; d) monitoring of ocean surface states using optical amd microwave airspace data sets.
The focus of our investigation (1975-1995, see "Publication List") has been analysis of multiphase ocean surface structures including foam, whitecaps, spray, underwater bubble populations, oil emulsions, young ice. For example the effects of high microwave emission of foam and whitecaps are due to specific absorption and scattering properties of bubbles.
Important issue is spray and underwater bubbles. It was shown that effects due to spray can yield both positive and negative brightness temperature contrasts. The spectrum of microwave radiation at mm- and cm- ranges depends on droplets' size distribution and "optical" thickness of spray clouds. At the same time emissivity variations due to underwater air bubbles are significant at long-microwave ranges of radiation which is connected with the sharp change of skin-layer depth.
Another problem is a global distribution of wave breaking field at the storm conditions. This investigations are made by means of airspace photography and optical image processing. In particular we have found that size histograms and fractal dimensions differ for foam streaks and whitecaps and vary depending on wind wave generation state and fetch. The idea of fractal dimension has resolved the problem of ocean surface state quantization using remote sensing techniques.
On the basis of optical and microwave investigations a composite microwave model model of ocean-atmosphere system is designed. This model take into account not only the structural hierarchy of natural multiphase media in air-water interface but also the dynamic characteristics of ocean boundary layer and statistics of foam coverage and whitecaps. Some dynamic weight coefficients as area fractions of different types of interface factors (foam formations, spray, underwater bubbles, large- and small-scale wind waves, turbulence roughness and other) are introduced in the composite model.
Multifreguency microwave radiometric complex at 1,4 - 37 GHz and airspace optical devises with a high spatial resolution could be used. Also side-looking radar (SLAR) or synthetic aperture radar (SAR) would be desirable for identification of the ocean-atmospheric stratifications including internal waves.
The concept of combined optical microwave technique based on physical background will be applied to further investigations which are supposed to be carried out according to the research proposal. The main scientific problem is the determination of local and spatial nonuniform ocean surface characteristics by means of microwave, radar and optical remote sensing techniques.
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