Open AccessGlobal simulations of ice nucleation and ice supersaturation with an improved cloud scheme in the Community Atmosphere Model
Author(s) -
Gettelman A.,
Liu X.,
Ghan S. J.,
Morrison H.,
Park S.,
Conley A. J.,
Klein S. A.,
Boyle J.,
Mitchell D. L.,
Li J.L. F.
Publication year - 2010
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jd013797
Subject(s) - ice nucleus , sea ice growth processes , supersaturation , ice cloud , atmospheric sciences , nucleation , ice crystals , cloud forcing , environmental science , cloud condensation nuclei , climatology , arctic , radiative forcing , aerosol , meteorology , arctic ice pack , sea ice , geology , sea ice thickness , physics , radiative transfer , thermodynamics , oceanography , quantum mechanics
A process‐based treatment of ice supersaturation and ice nucleation is implemented in the National Center for Atmospheric Research Community Atmosphere Model (CAM). The new scheme is designed to allow (1) supersaturation with respect to ice, (2) ice nucleation by aerosol particles, and (3) ice cloud cover consistent with ice microphysics. The scheme is implemented with a two‐moment microphysics code and is used to evaluate ice cloud nucleation mechanisms and supersaturation in CAM. The new model is able to reproduce field observations of ice mass and mixed phase cloud occurrence better than previous versions. The model is able to reproduce observed patterns and frequency of ice supersaturation. Simulations indicate homogeneous freezing of sulfate and heterogeneous freezing on dust are both important ice nucleation mechanisms, in different regions. Simulated cloud forcing and climate is sensitive to different formulations of the ice microphysics. Arctic surface radiative fluxes are sensitive to the parameterization of ice clouds. These results indicate that ice clouds are potentially an important part of understanding cloud forcing and potential cloud feedbacks, particularly in the Arctic.