Cloud Property Retrieval Using Combined Ground-Based Remote Sensors
Wang, Z. and Sassen, K., University of Utah
Eleventh Atmospheric Radiation Measurement (ARM) Science Team Meeting
The Atmospheric Radiation Measurements Program (ARM) is making measurements with diverse ground-based remote sensors. To provide more complete and accurate cloud information, it is necessary to combine diverse measurements because of the different capabilities of various sensors. In this study, a remote sensing cloud detection algorithm has been developed that can differentiate between various atmospheric targets such as ice and water clouds, virga, precipitation, and aerosol layers. Cloud type and macrophysical properties are identified by combining ground-based polarization lidar, millimeter wave radar, infrared radiometer, and dual channel microwave radiometer measurements. These algorithms are applied to the measurements collected during the year of 1998 from the ARM Cloud and Radiation Testbed site in the South Great Plains (SGP). The statistics of cloud properties measured during this year are discussed, illustrating how extended time remote sensing datasets can be converted to cloud properties of concern to climate research. A retrieval algorithm is also presented to estimate cirrus cloud ice water content (IWC) and general effective size (Dge) profiles from lidar and radar measurements. In the algorithm, extinction coefficient is parameterized according to Fu (1996), and equivalent radar reflectivity factor (Ze) is parameterized as function of IWC and Dge by assuming a modified gamma size distribution and a hexagonal ice crystal shape. Case studies and comparisons with aircraft in situ measurements and other approaches indicate that the algorithm can provide reliable cirrus cloud microphysical properties. A technique to estimate ice water path and layer mean Dge is also developed using the optical depth and mean radar reflectivity factor of the cloud layer. The algorithm is applied to ~1000 hours Raman lidar and millimeter clouds radar data collected at the ARM SGP site during the period from November 1996 from November 2000, and basic statistics of cirrus microphysical and radiative properties, as well as their temperature and layer thickness dependences are discussed. These findings can be used to improve and validate cirrus parameterization in general circulation models.
Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).
