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Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM

Lohmann, U. and Stier, P. and Hoose, C. and Ferrachat, S. and Rockner, E. and Zhang, J. (2007) Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM. Atmospheric Chemistry and Physics Discussions, 7 (2). pp. 3719-3761. ISSN 1680-7367.

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The double-moment cloud microphysics scheme from ECHAM4 has been coupled to the size-resolved aerosol scheme ECHAM5-HAM. ECHAM5-HAM predicts the aerosol mass and number concentrations and the aerosol mixing state. This results in a much better agreement with observed vertical profiles of the black carbon and aerosol mass mixing ratios than with the previous version ECHAM4, where only the different aerosol mass mixing ratios were predicted. Also, the simulated liquid, ice and total water content and the cloud droplet and ice crystal number concentrations as a function of temperature in stratiform mixed-phase clouds between 0 and –35°C agree much better with aircraft observations in the ECHAM5 simulations. ECHAM5 performs better because more realistic aerosol concentrations are available for cloud droplet nucleation and because the Bergeron-Findeisen process is parameterized as being more efficient. The total anthropogenic aerosol effect includes the direct, semi-direct and indirect effects and is defined as the difference in the top-of-the-atmosphere net radiation between present-day and pre-industrial times. It amounts to –1.8 W m^−2 in ECHAM5, when a relative humidity dependent cloud cover scheme and present-day aerosol emissions representative for the year 2000 are used. It is larger when either a statistical cloud cover scheme or a different aerosol emission inventory are employed.

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Additional Information:© Author(s) 2007. This work is licensed under a Creative Commons License. Received: 22 February 2007 – Accepted: 8 March 2007 – Published: 12 March 2007. The authors are grateful for financial support from NCCR Climate. They thank J. Quaas and S. Kinne for providing satellite data, A. Korolev for providing the in-situ aircraft data, S. Kloster for providing aerosol emissions and the German Computing Centre (DKRZ) for computing time.
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Official Citation:Lohmann, U., Stier, P., Hoose, C., Ferrachat, S., Roeckner, E., and Zhang, J.: Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM, Atmos. Chem. Phys. Discuss., 7, 3719-3761, 2007.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9203
Deposited By: Archive Administrator
Deposited On:20 Nov 2007
Last Modified:02 Oct 2019 23:58

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