Sensitivity of CAM5-Simulated Arctic Clouds and Radiation to Ice Nucleation Parameterization
©2013 American Meteorological Society. Sensitivity of Arctic clouds and radiation in the Community Atmospheric Model, version 5, to the ice nucleation process is examined by testing a new physically based ice nucleation scheme that links the variation of ice nuclei (IN) number concentration to aeros...
Published in: | Journal of Climate |
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Main Authors: | , , , |
Format: | Other Non-Article Part of Journal/Newspaper |
Language: | English |
Published: |
University of Wyoming. Libraries
2013
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Subjects: | |
Online Access: | https://hdl.handle.net/20.500.11919/714 https://doi.org/10.1175/JCLI-D-12-00517.1 |
Summary: | ©2013 American Meteorological Society. Sensitivity of Arctic clouds and radiation in the Community Atmospheric Model, version 5, to the ice nucleation process is examined by testing a new physically based ice nucleation scheme that links the variation of ice nuclei (IN) number concentration to aerosol properties. The default scheme parameterizes the IN concentration simply as a function of ice supersaturation. The new scheme leads to a significant reduction in simulated IN concentration at all latitudes while changes in cloud amounts and properties are mainly seen at high- and midlatitude storm tracks. In the Arctic, there is a considerable increase in midlevel clouds and a decrease in low-level clouds, which result from the complex interaction among the cloud macrophysics, microphysics, and large-scale environment. The smaller IN concentrations result in an increase in liquid water path and a decrease in ice water path caused by the slowdown of the Bergeron-Findeisen process in mixed-phase clouds. Overall, there is an increase in the optical depth of Arctic clouds, which leads to a stronger cloud radiative forcing (net cooling) at the top of the atmosphere. The comparison with satellite data shows that the new scheme slightly improves low-level cloud simulations over most of the Arctic but produces too many midlevel clouds. Considerable improvements are seen in the simulated low-level clouds and their properties when compared with Arctic ground-based measurements. Issues with the observations and the model- observation comparison in the Arctic region are discussed. |
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