Remote-Sensing Technologies and Data Processing Algorithms - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 174

spectral dependencies of the second, s parameters on

microwave Sun radiation dispersed as a result of rain intensity increasing are dis-
placed to the low-frequency region (up to

third, and fourth Stock '

6 GHz). So, for the rain layer having
the thickness in 4 km under the Sun observation under corner in 20

≈

regarding the
horizont the maximal values of S 2 , S 3 and S 4 are achieved under the rain intensity
r = 12.5 mm h − 1 and for the frequency

°

13.5 GHz. They are equaled: S 2 = 220 K,
S 3 = 44.6 K and S 4 = 5.95 K. When r =50mmh − 1 and frequency

≈

6 GHz these
parameters are the following: S 2 = 483 K, S 3 = 101.5 K, and S 4 = 28.5 K.
Polarization radiometry of precipitation is based on two effects: the nonspherical
form of rain drops and the existence of a distinct direction in which the symmetrical
axes of falling drops are oriented. This means that the emission and absorption of
radio waves having vertical and horizontal polarizations that differ in directions
from the orientation of symmetrical axes of rain drops can be distinguished. For this
reason the azimuth simmetry of radiothermal

≈

field of the rain emission is absent.
And this means that microwave emission of the rain is partly polarized. Therefore,
the task of precipitation diagnostics is reduced to finding the degree of dependence

of the emission polarization parameters (polarization degree, slop angle of polari-
zation plane, polarization ellipse form, etc.) on characteristics of the state of the
environment in which rain is dispersing.
The

first polarization radiometric measurements of the rain descending micro-
wave emission were realized by Kutuza (1977), and then were motivated and
developed by the experiments and theoretically in the subsequent investigations.
The results of measurements of T j in general and difference channels of microwave
radiometer at = 2.25 cm (13.3 GHz) given the estimations of degree of linear

polarization of rain radio-emission. When intensity of steady downpour was
changed between 0.5 and 2.5 mm h − 1 it was equaled to 5.5 %. The rains having the
convective type with the intensity more 5 mm h − 1 had the degree of linear polar-
ization which was increased until 8.5 %. These estimations guarantee the distinct
delimitation of the rain zones.
The methodology set up to estimate the parameters involved in the distribution
of rain drops by size developed by Gasiewski and Kunkee (1994) is based on the
measurements of two Stock

ʻ

s parameters, S 1 and S 2 . The gist of methodology
consists in solving an inverse task under the preposition that non-spherical drops
have an exponential distribution with two unknown parameters determined by the
data about S 1 and S 2 . The contribution of values of third and fourth Stock

'

s
parameters to the solution of rain diagnostics task is determined by the expansion of
estimated parameters. So, S 3 is proportional to the differential relaxation,

'

ʔ 1 ,of

radiowave. The fourth Stock ' is parameter is proportional to the product of ʔ 1 and

differential phase displacement, ʔ 2 is called as the rain

anisotropy parameter and it can be measured directly. Theoretical dependencies of
ʔ

ʔ 2 . A value of ʔ = ʔ 1 + i

from different parameters of the rain are studied by Gasiewski and Kunkee
(1994). It was shown that the spreading in the distribution by the slop corner to the
vertical of projections of drops symmetry axis in the plane which is orthogonal to
the direction of wave spreading exercise largest in ʔ

estimation. Statistical models describing the orientation of drops allow the average

fl uence on the precision of