Vertical profiles of Arctic haze aerosol in spring 1994 obtained by using spectrophotometric measurements

During a joint Russian-German Arctic airborne expedition in March-April 1994, measurements of direct solar radiation fluxes were conducted. The atmosphere optical depths and vertical distributions of aerosol extinction coefficients were obtained for various regions in the Russian and Canadian sectors of the Arctic by using spectrophotometer which was installed aboard research aircraft I1-18 'Cyclone'. The aircraft observations were performed in a relatively short period of time, that gives a possibility to investigate practically instantaneous spatial distributions of arctic haze properties other the whole Arctic. It was found that the geographical variations of arctic haze properties were relatively small. Both in the Russian and in the Canadian sectors spectrophotometer detected deep and persistent layers of arctic haze between the ground and 2000 m level. Peak values of light extinction coefficients for wavelength 500 nm in these layers were more than 0.25 km(-1). In most cases, the surface arctic haze layers were embedded in temperature inversion. Practically all observations showed a presence of aerosol layers in free troposphere, a fact that had been treated early as a rather rare occasion for arctic haze. The altitude of this aerosol formation was 5-6 km. Vertical distribution of meteorological parameters showed an increase of relative humidity at these heights. (C) 1997 Elsevier Science B.V.