Studies of Stratocumulus and Fair-Weather Cumulus Clouds Using a 94 GHz Droppler Cloud Radar

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Abstract/Albrecht Many climate and forecast models are not able to account for shallow boundary layer clouds properly. The result of this deficiency is uncertainty in climate and long-range weather predictions. To provide an observational basis for improvement of cloud parameterizations and to increase understanding of key cloud processes, a 94 GHz Doppler radar will be used with other remote sensing systems and in situ aircraft observations to study continental stratocumulus and fair-weather cumulus clouds. This study will focus on processes that affect cloud lifetime and the production of large drops that serve as precursors to the formation of precipitation. A key, unique feature of this work is the deployment of the 94 GHz radar on a helicopter to enable researchers to study the entire life cycle of cumulus clouds. The continental stratus studies will use an extensive data set (more than 250 hours of cloud observations) from the cloud radar, a microwave radiometer, a ceilometer, and supporting meteorological observations that were collected over central Pennsylvania under prior NSF support. This will include investigations of large-eddy structures, entrainment processes, and the production of large drops and drizzle. An extensive set of observations of shallow cumuli will be made using a single-dish 94 GHz radar that has recendy been developed and constructed at the University of Miami. A ceilometer, a micropulse lidar, a microwave radiometer, an IR radiometer, and a video camera will be used to support the cloud structure measurements from radar operations at shoreline and inland sites in south Florida. The environment in which the clouds form will be characterized using rawinsondes and a 915 MHz wind profiler. In addition, an infrared interferometer will be available during some observing periods for the retrieval of boundary layer temperature and moisture profiles. The radar on a helicopter will be used to sample the dynamics and microphysics of clouds over their en tire life cycles as wind shear, stability, and aerosol conditions vary. This has not been tried and has great potential to improve the description of the spatial distribution and evolution of large-drop concentrations in fair-weather cumulus clouds and to determine whether the lifetime of small cumuli decreases when drizzle is produced. P:\Pmet\pmet awds, f7 & abst\Albrecht.abs