Ozone correction to the aerosol optical depth in the Chappius band.

Aerosol optical depth in the visible range is affected by ozone absorption (Chappuis band). In order to derive reliable information from extinction measurements of solar irradiance, a suitable correction has to be considered. Ozone correction based on climatological data sets has been proved ineffective. Better results are typically obtained on the basis of indirect methods which, nevertheless, require some nd hoc assumptions such as the wavelength dependence on aerosol optical depth. A validation of these indirect methods is provided in this paper. Direct estimations of ozone profiles have been derived from ultra-violet and visible spectral scattered solar radiation. The Umkehr method was resorted for implementing a suitable inversion scheme for the ozone profile. Our results show that indirect ozone correction procedures are really capable of yielding absorption ozone-free aerosol optical depth. (C) 1998 Elsevier Science Ltd. All rights reserved.