Microphysical properties of continental clouds from in situ measurements

It is important to gain knowledge about the microphysical characteristics of continental clouds in order to properly understand their formation, their radiative properties and their ability to produce precipitation. Satellites to remotely sense cloud properties, and cloud interactions with aircraft that fly through them require knowledge of cloud microphysics. Moreover, numerical simulations of global climate are sensitive to small systematic changes in cloud optical proper-ties, but very few large datasets are available that document the characteristics of continental clouds. This paper summarizes 9 X 10(4) km of in-cloud measurements made by the Central Aerological Observatory over the former USSR during 1977-84. Statistical characteristics of total water content (W), extinction coefficient (beta), effective diameter (D-eff) and effective concentration (N-eff) are summarized as functions of temperature and cloud type, for measurements archived at 700 m horizontal resolution. The effect of threshold sensitivity, or cloud definition, on the statistical distributions is discussed. Decreases of W, and N-eff with colder temperatures are consistent with our general knowledge of cloud formation. For all temperature intervals and cloud types, correlations between pairs of W, beta and D-eff are too small thereby barring any hope of simple linear parametrizations. Differences in W, beta, D-eff and N-eff for the various cloud types indicate changes in cloud formation mechanisms. These data can assist in verification studies of cloud parametrization schemes in general-circulation models, numerical weather-prediction models, and cloud-resolving models. The problems of cloud type, scale averaging, variability over a model grid cell, distribution of water between the liquid and ice phase, and the lumping together of precipitating and non-precipitating clouds must be considered in these studies.