SUN-PHOTOMETER OBSERVATIONS OF AEROSOL OPTICAL-THICKNESS OVER THE NORTH-ATLANTIC FROM A SOVIET RESEARCH VESSEL FOR VALIDATION OF SATELLITE MEASUREMENTS

This paper deals with the problem of aerosol optical thickness (tau(A) ) retrieval using sun-photometer measurements. The results of the theo retical analysis and computer processing of the dataset collected duri ng the 40th cruise of the R/V Akademik Vernadsky are presented. Accura cy of retrieved tau(A) is investigated in detail. It is concluded that 1) the tau(A) measurements from the three shortest wavelength channel s are sufficiently accurate (0.02-0.03) for evaluation of the NOAA Adv anced Very High Resolution Radiometer aerosol optical thickness operat ional product 2) serious discrepancies exist between observation and t heory for the two longest wavelength channels, which preclude their us e in aerosol optical property studies. Further investigations are requ ired, with emphasis on the computation of atmospheric gaseous absorpti on, before these channels can be used. Shipboard tau(A) will be compar ed with satellite data from the NOAA/National Environment Satellite Da ta and Information Service in a subsequent paper.