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Sensitivity Studies of Dust Ice Nuclei Effect on Cirrus Clouds with the Community Atmosphere Model CAM5In this study the effect of dust aerosol on upper tropospheric cirrus clouds through heterogeneous ice nucleation is investigated in the Community Atmospheric Model version 5 (CAM5) with two ice nucleation parameterizations. Both parameterizations consider homogeneous and heterogeneous nucleation and the competition between the two mechanisms in cirrus clouds, but differ significantly in the number concentration of heterogeneous ice nuclei (IN) from dust. Heterogeneous nucleation on dust aerosol reduces the occurrence frequency of homogeneous nucleation and thus the ice crystal number concentration in the Northern Hemisphere (NH) cirrus clouds compared to simulations with pure homogeneous nucleation. Global and annual mean shortwave and longwave cloud forcing are reduced by up to 2.0+/-0.1Wm (sup−2) (1 uncertainty) and 2.4+/-0.1Wm (sup−2), respectively due to the presence of dust IN, with the net cloud forcing change of −0.40+/-0.20W m(sup−2). Comparison of model simulations with in situ aircraft data obtained in NH mid-latitudes suggests that homogeneous ice nucleation may play an important role in the ice nucleation at these regions with temperatures of 205-230 K. However, simulations overestimate observed ice crystal number concentrations in the tropical tropopause regions with temperatures of 190- 205 K, and overestimate the frequency of occurrence of high ice crystal number concentration (greater than 200 L(sup-1) and underestimate the frequency of low ice crystal number concentration (less than 30 L(sup-1) at NH mid-latitudes. These results highlight the importance of quantifying the number concentrations and properties of heterogeneous IN (including dust aerosol) in the upper troposphere from the global perspective.
Document ID
20140001044
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Liu, Xiaohong
(Pacific Northwest National Lab. Richland, WA, United States)
Zhang, Kai
(Pacific Northwest National Lab. Richland, WA, United States)
Jensen, Eric J.
(NASA Ames Research Center Moffett Field, CA, United States)
Gettelman, Andrew
(National Center for Atmospheric Research Boulder, CO, United States)
Barahona, Donifan
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nenes, Athanasios
(Georgia Inst. of Tech. Atlanta, GA, United States)
Lawson, Paul
(Spec, Inc. Boulder, CO, United States)
Date Acquired
March 5, 2014
Publication Date
December 19, 2012
Publication Information
Publication: Atmospheric Chemistry and Physics
Volume: 12
Subject Category
Geophysics
Report/Patent Number
GSFC-E-DAA-TN8100
Funding Number(s)
WBS: WBS 802678.02.17.01.07
CONTRACT_GRANT: NNG11HP16A
CONTRACT_GRANT: DE-AC06-76RLO 1830
Distribution Limits
Public
Copyright
Public Use Permitted.
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