[1] The difference between cirrus emissivities at 8 and 11 mm is sensitive to the mean effective ice crystal size of the cirrus cloud, D e . By using single scattering properties of ice crystals shaped as planar polycrystals, diameters of up to about 70 mm can be retrieved, instead of up to 45 mm assuming spheres or hexagonal columns. The method described in this article is used for a global determination of mean effective ice crystal sizes of cirrus clouds from TOVS satellite observations. A sensitivity study of the D e retrieval to uncertainties in hypotheses on ice crystal shape, size distributions, and temperature profiles, as well as in vertical and horizontal cloud heterogeneities shows that uncertainties can be as large as 30%. However, the TOVS data set is one of few data sets which provides global and long-term coverage. Having analyzed the years 1987-1991, it was found that measured effective ice crystal diameters D e are stable from year to year. For 1990 a global median D e of 53.5 mm was determined. Averages distinguishing ocean/land, season, and latitude lie between 23 mm in winter over Northern Hemisphere midlatitude land and 64 mm in the tropics. In general, larger D e s are found in regions with higher atmospheric water vapor and for cirrus with a smaller effective emissivity.

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A new optical pulse train configuration that may propagate with high stability, in normal and anomalous dispersion regimes,in optical fibres is proposed and simulated using pulse position modulation (PPM) coding. The high stability is achieved by simultaneous propagation of two infinite and periodic trains of bright pulses in normal and anomalous dispersion regimes (solitons) in a single-mode optical fibre. This configuration could lead to transmission velocities around 300 Gb/s with good stability under PPM coding. PACS No.: 78.00

The inversion of TIROS-N Operational Vertical Sounder (TOVS) measurements by the Improved Initialization Inversion (31) Algorithm provides cloud parameters as well as atmospheric temperature and water vapor profiles. By the use of a cirrus radiation scheme based on Anomalous Diffraction Theory, that includes analytical expressions for extinction and absorption coefficients as function of ice particle shapes, size distribution parameters and wavelength, we study the possibility to infer information on cirrus microphysics at global scale from 31 data.