Analysis of the spatial inhomogeneities in stratocumulus and cumulus clouds

Spatial inhomogeneities in clouds have a lot of consequences especially in both radiative properties and internal mechanisms in relation with effects of mixing. We are concerned by the representation of these inhomogeneities for spatial scale in the range of 10 m to several ten kilometers in cases of stratocumulus and cumulus clouds. These clouds are characterized by means of threshold of the droplet concentration measured with an aircraft during thwo experiments: NEPHOS-1982 and FRONTS-1984. In the cases of stratocumulus (NEPHOS-1982) we use only droplets with diameters less than 30 mu m, while in the case of cumulus clouds (FRONTS-1984) we use both little droplets (diameters less than 30 mu m) and hydrometeors (probably ice crystals) with diameters greater than 60 mu m. The probability distribution to obtain a cloudy segment or a clear-air segment with a fixed length is described by a power-law which is characteristic for a geometrical scaling range. A possibility for the existence of scaling exponents is discussed with a very simple model of cloud mixing in relation to turbulence. We discuss consequences of scaling law for a parameterization of the cloud surface and the possibility for the non-unicity of this scaling.