Determination of Parameters of the Atmosphere and the Surface in a Clear Atmosphere - Short-Wave Solar Radiation in the Earth's Atmosphere - page 190

The derivatives with respect to ozone content reach the maximum in the
stratospheric ozone layer. Note that the selection of the upper boundary at
level 0.5mbar is determined with the influence of the stratospheric ozone
on the solar irradiance value because the influence of all other components
(including the aerosols) is negligibly weak at the high altitudes. The maximal
irradiance variation at wavelength 330 nm isabout5%totherangeofthe
a priori ozone variations.
The values of the derivatives with respect to N 2 O content are very low, and,
even with accounting for the possible wide interval of its a priori variations,
the retrieval of N 2 O content is impossible. This conclusion does not contradict
the results obtained in the previous section as we have used the extremely high
values of the absorbing gases content there and have calculated the derivatives
for the averaged model (Rozanov et al. 1995; Kneizis et al. 1996). The analo-
gous situation is arising for NO 3 gas, although the derivatives with respect to
N 2 O content within the absorption maximums (bands 524 and 662 nm)are
essentially greater and allow principally obtaining certain information about
NO 3 contents with its high concentration.
The derivatives with respect to volume coefficient of the aerosol scattering are
specified with the complicated vertical dependence. The volume coefficient of
the aerosol scattering influences to the solar irradiances owing to two contrary
processes: the irradiances are decreasing with the aerosol optical thickness
growth and are increasingwith the aerosol scattering growth. Thus, the profiles
of the derivatives in question are sign-invertible: they have a positivemaximum
around the observational point, which is decreasing with holding away from
this point and then they transform to the negative ones. Evidently, this obstacle
is connected with the local character of the scattering yield to the irradiances:
it is maximal around the point of the measurement. The absolute value of
the derivatives with respect to volume coefficient of the aerosol scattering
is quite high: the variations of the coefficient even in separate layers could
cause the irradiance variations up to 10% and higher. The spectral behavior
of the derivatives in question is weakly expressed. There is an approach for
retrieval of the altitudinal dependence of the aerosol parameters from the
remotemeasurements within the 760 nmoxygen absorption band (Badaev and
Malkevitch 1978; Timofeyev et al. 1995). Indeed, there is a certain difference
between the vertical profiles shape of the derivatives within this band and
out of it but it is rather weak that is also provided by the conclusion of the
study (Timofeyev et al. 1995). However, the vertical profile of the retrieved
parameters is directly obtained from the airborne observations at different
levels of the atmosphere.
The derivatives with respect to volume coefficient of the aerosol absorption
greatly depend on the type of the selected aerosol model. The values are greater
if the aerosol absorption is stronger. It is the reason why the retrieval of the
aerosol absorption volume coefficient from the data of the observations above
LadogaLakehasturnedoutadifficultproblemandithasbeenmuchmore
possible for the observations above the desert. The same conclusion is followed
from the analysis of the irradiances accomplished in Sect. 3.3.