THE POTENTIAL OF 8-MM RADARS FOR REMOTELY SENSING CLOUD DROP SIZE DISTRIBUTIONS

This paper describes the use of a vertically pointing 8.6-mm-wavelengt h Doppler radar for measuring drop size spectra in clouds. The data us ed were collected in the Atlantic Stratocumulus Transition Experiment in 1992. This paper uses the full Doppler velocity spectrum from the t ime series of Doppler radial velocities to extract information farther into the small-drop regime than previously attempted. The amount of l iquid residing in the cloud regime is compared with that found in the precipitation regime where drop fall velocities are resolvable. Total liquid is compared with that measured with a collocated three-channel microwave radiometer. Examples of number density spectra, liquid water spectra, and flux spectra are shown and compared with what is known o f these quantities from various in situ measurements by aircraft in si milar clouds. Error estimates and uncertainties are discussed. It is c oncluded that 8-mm Doppler radars have the potential for broader use i n cloud and precipitation studies than generally realized.