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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 16, issue 4 | Copyright
Atmos. Chem. Phys., 16, 2611-2629, 2016
https://doi.org/10.5194/acp-16-2611-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 03 Mar 2016

Research article | 03 Mar 2016

Understanding cirrus ice crystal number variability for different heterogeneous ice nucleation spectra

Sylvia C. Sullivan1, Ricardo Morales Betancourt2, Donifan Barahona3, and Athanasios Nenes1,4,5,6 Sylvia C. Sullivan et al.
  • 1Department of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
  • 2Department of Civil and Environmental Engineering, University of Los Andes, Bogotá, Colombia
  • 3NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 4Department of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA
  • 5ICE-HT, Foundation for Research and Technology, Hellas, 26504 Patras, Greece
  • 6IERSD, National Observatory of Athens, Palea Penteli, 15236, Greece

Abstract. Along with minimizing parameter uncertainty, understanding the cause of temporal and spatial variability of the nucleated ice crystal number, Ni, is key to improving the representation of cirrus clouds in climate models. To this end, sensitivities of Ni to input variables like aerosol number and diameter provide valuable information about nucleation regime and efficiency for a given model formulation. Here we use the adjoint model of the adjoint of a cirrus formation parameterization (Barahona and Nenes, 2009b) to understand Ni variability for various ice-nucleating particle (INP) spectra. Inputs are generated with the Community Atmosphere Model version 5, and simulations are done with a theoretically derived spectrum, an empirical lab-based spectrum and two field-based empirical spectra that differ in the nucleation threshold for black carbon particles and in the active site density for dust. The magnitude and sign of Ni sensitivity to insoluble aerosol number can be directly linked to nucleation regime and efficiency of various INP. The lab-based spectrum calculates much higher INP efficiencies than field-based ones, which reveals a disparity in aerosol surface properties. Ni sensitivity to temperature tends to be low, due to the compensating effects of temperature on INP spectrum parameters; this low temperature sensitivity regime has been experimentally reported before but never deconstructed as done here.

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We use the adjoint model of a cirrus parameterization to quantify sources of crystal variability for various ice-nucleating spectra and output from CAM5. The sensitivities can be directly linked to nucleation regime and efficiency of various INP. The lab-based spectrum calculates much higher INP efficiencies than field-based ones, owing to aerosol surface properties. The sensitivity to temperature tends to be low, due to the compensating effects of temperature on INP spectrum parameters.
We use the adjoint model of a cirrus parameterization to quantify sources of crystal variability...
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