Upper Tropospheric Ice Nuclei Measurements in CRYSTAL-FACE (The Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment) PI's: Paul DeMott (CSU)         Sonia Kreidenweis (CSU)         David Rogers (NCAR)

Data access via CRYSTAL-FACE Program Web Site

Overview

The overall objectives of the CRYSTAL-FACE program are described on the program web site. Our particular investigations included the following objectives and approaches: 1) Identify the properties and concentrations of ice nucleating aerosols that might feed convective cells in the tropics, either via entry through cloud base or entrainment into the clouds in middle and upper levels, and thereby affect the microphysical properties of anvil cirrus clouds. Measurements were made using the CSU CFDC installed on the University of North Dakota Citation aircraft. 2) Evaluate the role of different ice formation processes (homogeneous and heterogeneous ice nucleation, secondary ice formation) in determining the microphysical composition of convective anvils in the Florida area. The approach was to compare and contrast CFDC measurements of the ice nucleating properties of anvil crystal residual nuclei (collected by a counterflow virtual impactor - Cynthia Twohy, PI) with actual cirrus particle measurements. 3) Provide explicit guidance on ice nucleation for numerical cloud model simulations of tropical cirrus. 4) Identify, chemically, the likely sources of ice nuclei to clouds in CRYSTAL-FACE, differentiating, as possible, between different ice formation mechanisms.

Results and Publications

African dust as ice nuclei

Ice formation processes in convective clouds and impacts on anvil cirrus composition