Geoscience Reference
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calculated by the using of thermal radioemission. Hence the microwave radiometry
can be used for the monitoring of reservoirs pollution.
The emissive and re
ective abilities of a sea surface in microwave region is very
connected with ocean environment parameters such as the water temperature,
salinity, dielectric constant, and roughness. Sasaki et al. (1988) shown that 6.7
fl
-
18.6 GHz band has high informativity to diagnose the atmosphere-ocean system. It
was established that correlation between radiobrightness temperatures of atmosphere
and sea surface has linear character and that re
ective ability on horizontal polari-
zation at the frequency 18.6 GHz is higher then on vertical polarization. Moreover, it
is observed that there exists an obvious dependence of radiobrightness temperature
fl
fl
fluctuations of the sea surface on wind speed. It equals for the horizontal polarization
to 0.5 and 1.0 K m
−
1
s at 6.7 and 18.6 GHz, respectively. In the case of vertical
polarization these values equal to 0.3
1.5 K m
−
1
s, respectively.
The sensitivity of the sea surface brightness temperature, T
BP
(K), for the
polarization P-type to the variations in the wind speed, V(m s
−
1
) is determined by
value (Figs.
2.30
and
2.31
):
0.8 and 0.6
-
-
x
¼
@
T
BP
@
;
a
1
; ...;
a
k
¼const
V
, k) are the oceanic environmental parameters contributing to
T
BP
change except for wind speed. The value of
where a
i
(i =1,
…
is almost linearly correlated with
wind speed at constant sea surface temperature and salinity, so
@
ˉ
2
T
BP
=@
V
2
0.
Then T
BP
¼ T
BOP
ðhÞþ
V
@
T
BP
ðhÞ=@
V, where T
BOP
is the brightness temperature of
the calm sea surface (K),
ʸ
is the zenith angle of incident radiation. According to the
Kirchoff
'
s law we have the following wind speed sensitivity of
re
fl
ectiv-
ity:
@c
P
ðhÞ=@
V ¼
@e
P
ðhÞ=@
V. It gives the following expression for re
fl
ectivity at
Fig. 2.30 Empirical
dependence of brightness
temperature of ocean surface
on the wind speed at various
wavelengths and the
observation angles (Sasaki
et al. 1988). The frequencies
in GHz are given on the
curves
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