Superposition of surface imprints of oceanic and atmospheric phenomena on RAR and SAR images of the ocean

There is an optimal range of wind speed W favorable for registration of surface wind variations. At the W values below a threshold level (it depends on radar wavelength and incidence angle and on sea surface temperature (SST) also) small-scale roughness responsible for backscatter is practically absent and radar does not "see" weak wind speed variations. At strong winds intensity of backscatter signal (normalized radar cross section-NRCS) is high. Radar observations of oceanic phenomena are somewhat distinct: in most cases the presence of small-scale roughness is a necessary condition for their registration. In this case, wind speed should fall in the range between 2-3 and 7-10 m/s. It is precisely this roughness modulation that is responsible for surface imprints of the oceanic phenomena. Small-scale roughness is thus an analog of light-sensitive photo emulsion. The most intensive oceanic phenomena, however, are a source of small-scale roughness by itself and can be detected by radar against the calm sea surface background. Parameters of the uppermost layer of the ocean, first of all SST and concentration of surface film, can have a pronounced effect on efficiency of radar sensing phenomena on each side of the sea surface, all factors being the same. This effect is due to joint action of several direct and indirect mechanisms. The SST decrease is accompanied by the decrease in roughness due to the increase in a kinematic viscosity.