Abstract
A new treatment of mixed-phase cloud microphysics has been implemented in the general circulation model, Community Atmosphere Model (CAM)-Oslo, which combines the NCAR CAM2.0.1 and a detailed aerosol module. The new treatment takes into account the aerosol influence on ice phase initiation in stratiform clouds with temperatures between 0° and −40°C. Both supersaturation and cloud ice fraction, that is, the fraction of cloud ice compared to the total cloud water in a given grid box, are now determined based on a physical reasoning in which not only temperature but also the ambient aerosol concentration play a role. Included in the improved microphysics treatment is also a continuity equation for ice crystal number concentration. Ice crystal sources are heterogeneous and homogeneous freezing processes and ice multiplication. Sink terms are collection processes and precipitation formation, that is, melting and sublimation. Instead of using an idealized ice nuclei concentration for the heterogeneous freezing processes, a common approach in global models, the freezing processes are here dependent on the ability of the ambient aerosols to act as ice nuclei. Additionally, the processes are dependent on the cloud droplet number concentration and hence the aerosols’ ability to act as cloud condensation nuclei. Sensitivity simulations based on the new microphysical treatment of mixed-phase clouds are presented for both preindustrial and present-day aerosol emissions. Freezing efficiency is found to be highly sensitive to the amount of sulphuric acid available for ice nuclei coating. In the simulations, the interaction of anthropogenic aerosols and freezing mechanisms causes a warming of the earth–atmosphere system, counteracting the cooling effect of aerosols influencing warm clouds. The authors find that this reduction of the total aerosol indirect effect amounts to 50%–90% for the specific assumptions on aerosol properties used in this study. However, many microphysical processes in mixed-phase clouds are still poorly understood and the results must be interpreted with that in mind.
References
68
Referenced
91
10.1029/1999JD901161
10.1126/science.245.4923.1227
-
Andreae, M. O., C. D. Jones, and P. M. Cox, 2005: Strong present-day aerosol cooling implies a hot future. Science, 435,1187–1190.
(
10.1038/nature03671
) 10.1002/joc.774
10.1029/97GL03261
10.1175/1520-0469(2001)058<3224:POGCOF>2.0.CO;2
10.1175/1520-0442(1996)009<0270:APCWPF>2.0.CO;2
10.1029/97JD01138
10.1029/97GL03779
10.1073/pnas.2532677100
10.1175/1520-0469(2004)061<2063:HDFITI>2.0.CO;2
10.1029/2005JD005884
10.1029/2005JD006627
10.1029/91JD02472
10.1029/2000JD900502
10.1016/S0021-8502(00)00077-X
10.1038/249026a0
10.1029/2001JD001143
10.1029/98GL01089
- Hoose, C., U. Lohmann, R. Erdin, and I. Tegen, 2007: Global influence of dust mineralogical composition on heterogeneous ice nucleation. Environ. Res. Lett., 3.025003, doi:10. 1088/1748-9326/3/2/025003.
10.1021/jp021593y
-
Intrieri, J. M., M. D. Shupe, T. Uttal, and B. J. McCarty, 2002: An annual cycle of Arctic cloud characteristics observed by radar and lidar at SHEBA. J. Geophys. Res., 107.8029, doi:10.1029/2000JC000423.
(
10.1029/2000JC000423
) 10.1016/S0169-8095(01)00111-9
10.1029/2001JD000885
10.1029/2003JD003840
10.1126/science.1106335
10.1029/93JD02334
-
Kärcher, B., and U. Lohmann, 2002: A parameterization of cirrus cloud formation: Homogeneous freezing of supercooled clouds. J. Geophys. Res., 107.4010, doi:10.1029/2001JD000470.
(
10.1029/2001JD000470
) 10.1029/2002JD003220
10.1126/science.309.5731.100
10.1029/94JD00941
10.1175/JTECH1720.1
10.1175/JAS3784.1
10.1256/qj.01.204
10.1029/2001JD000887
10.1029/2000JD900015
10.1175/1520-0450(1983)022<1964:CVIFOF>2.0.CO;2
10.1029/2005JD005810
- Levkov, L. B., B. Rockel, H. Kapitza, and E. Raschke, 1992: 3D mesoscale numerical studies of cirrus and stratus clouds by their time and space evolution. Beitr. Phys. Atmos., 65,35–58.
10.1175/1520-0469(2001)059<0647:PAEOIC>2.0.CO;2
10.1029/2001JD001101
10.5194/acp-5-715-2005
10.1175/JAS3662.1
10.1029/1999JD901199
10.5194/acp-7-3425-2007
10.1016/0169-8095(95)00017-8
10.1175/1520-0469(1996)053<2401:MCOTAS>2.0.CO;2
10.1175/1520-0469(2002)059<0692:GSOTAI>2.0.CO;2
10.1016/0169-8095(94)00014-5
10.5194/acp-6-3391-2006
10.1126/science.1135199
10.5194/acp-6-947-2006
10.1175/1520-0442(1998)011<1587:ACOTCM>2.0.CO;2
10.1029/97GL03478
10.1175/1520-0442(2003)016<3476:SOTFIA>2.0.CO;2
10.1029/2003GL017371
10.1175/1520-0469(1976)033<1554:BINPIT>2.0.CO;2
10.1111/j.1600-0870.2008.00318.x
10.1175/1520-0469(1989)046<1419:AGPFTS>2.0.CO;2
10.1029/2000JD900498
10.1029/2005JD006300
10.5194/acp-6-3583-2006
- Takemura, T., T. Nozawa, S. Emori, T. Y. Nakajima, and T. Nakajima, 2005: Simulation of climate response to aerosol direct and indirect effects with aerosol transport-radiation model. J. Geophys. Res., 110.D02202, doi:10.1029/2004JD00502.
10.5194/acp-6-1777-2006
10.1175/1520-0469(1977)034<1149:TIOPOT>2.0.CO;2
- Vali, G., 1985: Atmospheric ice nucleation—A review. J. Rech. Atmos., 19,105–115.
10.1080/07055900.1995.9649539
10.1175/1520-0450(2002)041<0384:ROICPU>2.0.CO;2
Dates
Type | When |
---|---|
Created | 17 years, 5 months ago (Feb. 29, 2008, 11:53 a.m.) |
Deposited | 4 years, 8 months ago (Dec. 7, 2020, 4:42 p.m.) |
Indexed | 1 year, 1 month ago (July 7, 2024, 9:55 a.m.) |
Issued | 16 years, 10 months ago (Oct. 1, 2008) |
Published | 16 years, 10 months ago (Oct. 1, 2008) |
Published Print | 16 years, 10 months ago (Oct. 1, 2008) |
@article{Storelvmo_2008, title={Aerosol Influence on Mixed-Phase Clouds in CAM-Oslo}, volume={65}, ISSN={1520-0469}, url={http://dx.doi.org/10.1175/2008jas2430.1}, DOI={10.1175/2008jas2430.1}, number={10}, journal={Journal of the Atmospheric Sciences}, publisher={American Meteorological Society}, author={Storelvmo, Trude and Kristjánsson, Jón Egill and Lohmann, Ulrike}, year={2008}, month=oct, pages={3214–3230} }