Doppler Wind Lidar Observations of Shallow Cumulus Clouds

Shallow cumulus clouds play an important role in surface energy budget and in transport of moisture, momentum and pollution from boundary layer to the free troposphere. These small, optically thin, short lived clouds have large variations in both time and space. Modeling of shallow cumulus clouds remains a significant challenge in global climate models and is of particular interest for solar forecasting. Simulations or parameterizations of shallow cumulus fields require measurements of several relevant quantities for validation. Here, we use Doppler wind lidar vertical velocity measurements to study key quantities related to the formation and maintenance of these clouds that need to be modeled properly. We characterize updraft fraction, coherent plume heights, plume width and mass flux velocity associated with these clouds. Doppler lidar measurements were made at Indianapolis, Indiana and the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site located in north-central Oklahoma. We compare and contrast these characteristics at the two locations in central United States that are particularly well suited for observations of shallow cumulus clouds. This analysis will extend previous similar analysis at the SGP central site to Indianapolis, Indiana, providing important information on regional variability.