Determination of Parameters of the Atmosphere and the Surface in a Clear Atmosphere - Short-Wave Solar Radiation in the Earth's Atmosphere - page 195

Fig. 5.6a,b. Results of the retrieval of the vertical volume ozone content profile: a from the
data of the airborne sounding 16th October 1983 above the Kara-Kum Desert; b from the
data of the airborne sounding 29th April 1985 above Ladoga Lake. Dotted line indicates the
aprioriprofile
Naats 1990; Vasilyev O and Vasilyev A 1994). Thus, the retrieved results could
be changed after correcting the aerosol model.
The systematic uncertainties of the instrument calibration strongly affect
the results of the vertical profiles of the coefficients in question (Vasilyev A
and Ivlev 1999). We illustrate this influence with the simplest example. Let the
measured value of the downwelling irradiance at the level 500mbar be system-
atically underestimated only for 1-2% (Sect. 3.3). The only way to adjust the
direct problem solution to this observational data is introducing the extinc-
tion aerosol layer to the model at the altitude higher than 500mbar.Taking
into account small a priori aerosol content at these altitudes, the introduced
aerosol layer must be sufficiently thick to cause the extinction of the down-
welling irradiance to 1-2%. Thus, even with the low systematic uncertainty in
the observed irradiances the algorithm of the inverse problem solving could
causethefalseconclusionabouttheexistenceoftheaerosollayersintheupper
troposphereandinthestratosphere.Hence,theresultsoftheretrievalofthe
aerosol scattering and absorption volume coefficients obtained in altitudinal
diapason of the airborne observations 500-950mbar are much more reliable,
because only the relative values of the solar irradiances are essential there. The
corresponding profiles are presented in Fig. 5.8. The calibrating factor is likely
to be introduced to the vector of the parameters for retrieval though it is make
the retrieval accuracy worse.