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Scattering ratios of the Pinatubo aerosol layer obtained by the ship‐borne lidar of the Roscomhydromet of Russia on‐board PROFESSOR ZUBOV are presented. During a campaign primarily in the low‐latitude (8°N–43°N) Atlantic Ocean, 48 days of data were obtained within the 73 day period spanning 11‐July and 21‐September of 1991 [Avdyushin et al., 1992]. These data show the aerosol cloud to be primarily in the 16–27 km altitude region, with a high degree of variability in the vertical structure and in the longitudinal structure, and to a lesser degree, in the latitudinal structure. Scattering ratios of up to 50 were recorded in the multi‐layered structure which was often observed. These are the first lidar observations showing a high degree of zonal variability of the vertical structure of the aerosol layer. We show the latitudinal range of the Pinatubo aerosol cloud in the northern hemisphere over a 2 month period and estimate the latitudinal dispersion rate for the months of the measurements to be approximately 5° latitude per month. A clear periodic variability was observed in the altitude structure during the entire data‐set primarily within 8°N–22°N latitude and within the altitude region of the layer, from which a mean zonal wind profile was produced by a spectral analysis of the aerosol profiles.

The vertical profiles of the extinction coefficient and the total optical thickness of the Pinatubo aerosol layer obtained from a network of 5 Rayleigh‐Mie lidars are presented here. Three ship‐borne lidars (PROFESSOR ZUBOV†, PROFESSOR VIZE†, HENRI POINCARE*) and two fixed lidar stations (OHP* and CEL*) are operated respectively by the Roscomhydromet†, of Russia and of the Service d'Aeronomie du CNRS* of France. The measurements presented are in the altitude range 15–35 km. They were obtained between July 1991 ‐ April 1992 and cover 8°S–60°N latitude and 80°W–6°E longitude. This represents extensive coverage of the western sector of the northern hemisphere, which is partly coincident with UARS satellite coverage. Optical depths of up to 0.2 were observed and maximum extinction coefficient values of 0.08 km−1 were obtained at 24 km and 18°N latitude.

Results of neutral temperature measurements in the polar thermosphere between 1968 and 1976 show a large variationas a function of the solar cycle. A very cold thermosphere associated with a high altitude for the mesopause is found at the maximum of solar activity.The amplitude of variation of neutral temperature at 165 km is 500øK, and the mesopause is observed to move from 120 to 90 km. Those resultsare attributed to the variation of both the amplitude and the altitude of turbulent processes as a function of solar activity. Theoretical calculations and experimental facts are in support of that explanation.