Collaborative Research: An Airborne Radar Study of Cloud Structure and Composition

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This grant supports a continuing collaboration between atmospheric scientists at the University of Wyoming and electrical engineers at the University of Massachusetts Amherst in the development and improvement of a 95 GHz (3.2 mm wavelength) radar and its application to studies of clouds and precipitation. The radar is ordinarily used in the Wyoming King Air research aircraft. Unlike ordinary weather radars, its short wavelength gives increased sensitivity to small drops and enables the radar to detect nonprecipitating clouds. Called the Wyoming Cloud Radar, it is capable of Doppler and polarimetric measurements. It will be mounted temporarily in the NCAR C-130 research aircraft for the DYCOMS-II project in July 2001 (Dynamics and Chemistry of Marine Stratocumulus). The data will give details on the cloud structure at the mixing region near cloud top and will also indicate the presence of drizzle, which is believed to have an important effect on the dynamics of the marine boundary layer. The capabilities of the WCR will be expanded by the addition of a second antenna in the King Air, which will permit dual-beam transmission for fine-scale observations of the horizontal wind field in convective clouds. The ideas will be tested in a field program in the High Plains (Colorado and Wyoming). The main research topics to be investigated are as follows:1. Relationships between CCN counts, drop concentration, and updraft speed.2. Horizontal wind field in different kinds of clouds.3. Entrainment in cumulus clouds.4. Drizzle formation in marine stratus clouds.5. Refinement of an attenuation-based method ("stereorad") for estimating cloud water content.Results are relevant to fundamental cloud physics, atmospheric remote sensing, and the parameterization of cloud effects in large-scale numerical models.