HR: 0800h
AN: A51A-0008    [Abstracts]
TI: Microphysical and Kinematic Structures Within Drizzling Stratocumulus in the Southeast Pacific
AU: * Comstock, K
EM: kcomstock@atmos.washington.edu
AF: University of Washington, Department of Atmospheric Sciences Box 351640, Seattle, 98195
AU: Yuter, S
EM: sandra_yuter@ncsu.edu
AF: North Carolina State University, Dept. of Marine, Earth, and Atmospheric Sciences Campus Box 8208, 1125 Jordan Hall, Raleigh, 27695
AU: Wood, R
EM: robwood@atmos.washington.edu
AF: University of Washington, Department of Atmospheric Sciences Box 351640, Seattle, 98195
AB: The role drizzle plays in the dynamics of the stratocumulus (Sc) topped boundary layer is uncertain and its parameterization difficult. Observations obtained during the 2001 East Pacific Investigation of Climate stratocumulus study (EPIC Sc) were designed to provide insight into the Sc physical processes with an eventual goal of improving model parameterizations. The unique EPIC data set combines comprehensive surface and ship-based remote sensing measurements and includes high temporal and spatial resolution data from both a vertically-pointing millimeter cloud radar (MMCR) and a scanning C-band radar. Recent findings based on ship and radar data from EPIC Sc show the importance of mesoscale (10-100 km) variability in both cloud and drizzle properties. To further these results, we use the C-band radar's high spatial-resolution RHI scans to characterize the detailed vertical structure of drizzle cells, including cells in all stages of their life cycle. This analysis defines two subsets of drizzle cells based on peak reflectivity: strong or high-reflectivity drizzle cells have cores greater than 15 dBZ, and moderate cells have peak reflectivity values of 5-15 dBZ. Results indicate that strong drizzle cells from both open-cell and closed-cell cloud regimes have quite similar microphysical and kinematic properties. Within drizzle cells, precipitation growth is evident from cloud top to just below cloud base. Drizzle cells are characterized by mesoscale patterns of convergence near cloud base and divergence near cloud top. Strong drizzle cells occurred more frequently in the open-cellular regime whereas closed-cellular regions contained more frequent moderate strength drizzle cells. Because drizzle potentially plays an important role in modulating the mesoscale circulations in Sc-topped boundary layers, these statistical characteristics of drizzle cells are important for cloud-resolving and other models to reproduce.
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005