Determination of both macrophysical and microphysical cloud properties on horizontal scales from a few tens of meters to hundreds of kilometers, based on measurements taken from surface, aircraft and satellite platforms, allow plane-parallel and fractal cloud models to be tested and tuned for various meteorological conditions. Fractal cascades designed for various cloud types generate cloud layers having a range of inhomogeneities, and Monte Carlo methods then determine the radiative properties of such clouds. Measurements of cloud radiative properties are conducted using airborne scanning radiometers and imaging spectrometers. The retrieved cloud properties from these measurements are compared with simultaneous in situ measurements of cloud microphysics. The methods have been used to develop remote sensing capability from spaceborne platforms, to study cloud properties in regional areas, and to study the interaction of clouds with aerosol particles and their combined climatic impact.
Recent activity involves measuring and studying the impact of ship effluents on cloud properties.
Existing on a small scale, ship tracks provide a useful laboratory for the study of cloud microphysical changes as well as tests of instrumentation and remote sensing and retrieval algorithms. The extrapolation of ship track measurements to the global-scale climate is a difficult problem which is still being studied. Further introductory information on clouds is in the NASA fact sheet on Clouds and the Energy Cycle .