Abstract. Measurements of upwelling and downwelling rain brightness temperatures show significant differences between horizontal and vertical polarization, which depend on wavelength and rain rate. These measurements are related to the first and second Stokes parameter. Also, the third Stokes parameter of atmospheric microwave emission will have measurable values under certain conditions. A polarimetric model for the description of the microwave emission and scattering by hydrometeors, including all four Stokes parameters, is presented. This model is applied to the scenario of plane layers of ice crystals and rain above a rough surface. The magnitudes of the third Stokes parameter for microwave emission from oriented nonspherical rain drops and for scattering by ice crystals are estimated. It is shown that the third Stokes parameter for rain is dominated by the first azimuthal harmonic of the emission vector. Finally, an algorithm for the computation of polarized brightness temperatures emanating from cylindrical rain cells above a surface is developed.
Calculations of attainable values for space resolution and radiometric sensibility of a spaceborne two‐dimensional synthetic aperture microwave polarimetric interferometer are carried out. It is shown that for the most preferable Y‐shaped interferometer configuration, it is possible to achieve (within the transparency windows of waveband 3–22.5 mm) a space resolution of 0.5–1 km and a radiometric resolution close to 1 K at the receiver bandwidth of 100 MHz. For cross‐ and T‐shaped resolutions, values close to the above can be reached.
The results of processing new experimental data on brightness temperature of atmospheric downwelling radiation near the resonance absorption line of water vapor 22.235 GHz are presented. The experiment was carried out by means of special 47-channel microwave radiometer-spectrometer. In this article the observations of stable clear sky and also cumulus cloud cover of various vertical extent for summer 2018-2019 measurement periods are considered. Due to assess the dynamics of brightness temperature fluctuations, the apparatus of Kolmogorov’s structural functions is used. Spectra of square root of structural function for wide range of temporal interval values under clear sky and cumulus cloud cover conditions are obtained. The two-frequency method of integral atmospheric moisture content evaluation is discussed. Experimental dependencies of cloud liquid water content on square root of structural function are shown.
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