HR: 16:00h
AN: A34B-01 INVITED     [Abstracts]
TI: Mid-Level Mixed-Phase Cloud Properties Derived From Polarization Lidar Measurements and Model Simulations
AU: * Sassen, K
EM: ksassen@gi.alaska.edu
AF: University of Alaska Fairbanks, 903 Koyukuk Drive , Fairbanks, AK 99775 United States
AU: Canonica, L
EM: canon@gi.alaska.edu
AF: University of Alaska Fairbanks, 903 Koyukuk Drive , Fairbanks, AK 99775 United States
AU: James, C
EM: campbell@gi.alaska.edu
AF: University of Alaska Fairbanks, 903 Koyukuk Drive , Fairbanks, AK 99775 United States
AU: Khvorostyanov, V
EM: 2318.g23@g23.relcom.ru
AF: Central Aeroloical Observatory, Dolgoprudny, Moscow, NA Russian Federation
AB: Water-dominated altocumulus clouds are distributed world-wide in the middle troposphere, and so are generally supercooled clouds with variable amounts of ice production via the heterogeneous droplet freezing process, which depends on temperature and the availability of ice nuclei. Although they tend to be relatively optically thin (i.e., for water clouds) and may often act similarly to cirrus clouds, altocumulus are globally widespread and probably play a significant role in maintaining the radiation balance of the Earth/atmosphere system. We will review recent cloud microphysical/ radiative model findings describing their impact on radiation transfer, and how increasing ice content (leading to cloud glaciation) affects their radiative impact. These simulations are based on the results of a polarization lidar climatology of the macrophysical properties of midlatitude altocumulus clouds, which variably produced ice virga. A new more advanced polarization lidar algorithm for characterizing mixed-phase cloud properties is currently being developed. Relative ice content is shown to have a large effect on atmospheric heating rates. We will also present lidar data examples, from Florida to Alaska, that indicate how desert dust and forest fire smoke aerosols can affect supercooled cloud phase. Since such aerosols may be becoming increasingly prevalent due to various human activities or climate change itself, it is important to assess the potential effects of increasing ice nuclei to climate change.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005