OZONE CORRECTION TO THE AEROSOL OPTICAL DEPTH IN THE CHAPPUIS BAND

Aerosol optical depth in the visible range is affected by ozone absorp tion (Chappuis band). In order to derive reliable information from ext inction 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 as sumptions such as the wavelength dependence on aerosol optical depth. A validation of these indirect methods is provided in this paper. Dire ct estimations of ozone profiles have been derived from ultra-violet a nd visible spectral scattered solar radiation. The Umkehr method was r esorted for implementing a suitable inversion scheme for the ozone pro file. Our results show that indirect ozone correction procedures are r eally capable of yielding absorption ozone-free aerosol optical depth. (C) 1998 Elsevier Science Ltd. All rights reserved.