TYPICAL VERTICAL PROFILES OF AEROSOL SPECTRAL EXTINCTION COEFFICIENTSDERIVED FROM OBSERVATIONS OF DIRECT SOLAR-RADIATION EXTINCTION DURINGTHE AIRCRAFT EXPERIMENTS ARCTIC-HAZE-94 95 AND MERISEC-93/94/

This paper presents first of all the method of observation of vertical profiles of aerosol spectral optical thickness and aerosol spectral e xtinction coefficients, taken during four campaigns as part of the Ger man-Russian aircraft project 'Arctic Haze/Merisec' in the years 1993, 1994 and 1995. These measurements reported here are concentrated on an episode on 5 April 1994 in the so-called 'Laptev Sea' box over a lati tude range from 82 degrees-86 degrees N and 197 degrees-117 degrees E, within a horizontal length of approximately 200 km, a width of nearly 40 km and a height up to the tropopause at about 8 km. Optical thickn ess and extinction values are presented for 6 heights within the tropo sphere, at 8 wavelengths varying from 0.4 up to 1.04 mu m. Aerosol ext inction coefficients are found to be in favourable agreement with thos e obtained from inferred values using optical aerosol particle data. E vidence of aerosol optical thickness of similar order of magnitude to near the ground level values has been found for aerosol layers some 10 0's m below the tropopause. (C) 1997 Elsevier Science B.V.