Microwave radiation of a cloudy atmosphere
Dr. Boris G. Kutuza, Institute
of Radio Engineering & Electronics
Moscow, Russia
It is shown that under conditions
of Rayleigh scattering, the temperature dependence of millimeter and centimeter
cloud absorption depends on the Debye parameter, which is characterized by the
water molecule relaxation time 
. Experimental data about
were obtained from measurement of solar emission at the
wavelengths of 0.4, 0.8, and 1.6 cm for different temperatures including the
region below the freezing level. Equations for the absorption coefficient are
given for isothermic and nonisothermic clouds.
We demonstrate the theoretical influence of different
cloud characteristics (temperature, liquid water content, water vapor, cloud
depth) on atmospheric downwelling radiation and upwelling radiation of the
ocean-atmosphere system. The difference in spectral characteristics of water vapor,
non-precipitating clouds and rain radiation as well as polarization of rain
radiation permit to use the microwave radiometric data for determination of
integral atmospheric parameters. The results of determination of liquid water
content in clouds and total water vapor mass by means of brightness temperature
measured from ground, aircraft and satellite are discussed.
Microwave
attenuation and emission of rain will be discussed. Experimental data about the
dual polarization of the rain thermal microwave emission due to drop
deformation are presented. Also, the third Stokes parameter of rain microwave
emission will have measurable values under certain conditions. Passive
measurements of rain show that the third Stokes parameter reaches values of
about 1-2% of the first Stokes parameter.