1982 .

(2 publications)

M. Ackerman, C. Lippens, C. Muller, and P. Vrignault. Blue sunlight extinction and scattering by dust in the 60-km altitude atmospheric region. Nature, 299:17-20, September 1982. [ bib | DOI | ADS link ]

Twilight data obtained photographically from a stratospheric balloon platform in the autumns of 1980 and 1981 and in the spring of 1982 are presented for blue and red light. They indicate the presence of a light absorbing layer and of a scattering layer in the mesosphere at altitudes near 60 plus or minus 10 km with a low scattering albedo (0.1) at 0.44 micron if it is accepted that both the extinction and scattering originate from dust. The optical efficiency of the layer increases more than 10 times when the wavelength of the interacting light changes from 0.65 to 0.44 micron. At the zenith and near sunset, the natural 0.44-micron extinction optical thickness and the sq cm column scattering rate due to this layer are found to be 0.066 and 0.18 MRA respectively on 3 May 1982 above the south-west of France.

M. Desbois, G. Seze, and G. Szejwach. Automatic Classification of Clouds on METEOSAT Imagery: Application to High-Level Clouds. Journal of Applied Meteorology, 21:401-412, March 1982. [ bib | DOI | ADS link ]

A statistical classification method based on clustering on three-dimensional histograms is applied to the three channels of the METEOSAT imagery [Visible (VIS)-Infrared Window (IR)-Infrared Water Vapor (WV)]. The results of this classification are studied for different cloud cover cases over tropical regions. For high-level cloud classes, it is shown that the bidimensional histogram IR-WV allows one to deduce the cloud top temperature even for semi-transparent clouds.