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| Titel |
Vertical velocity probability distributions simulated in the CAM-Oslo GCM |
| VerfasserIn |
C. Hoose, J. E. Kristjánsson, G. Svensson, S. Arabas, H. Pawlowska, J.-L. Brenguier |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026836
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| Zusammenfassung |
| Cloud droplet activation is calculated as a function of aerosol number, size and composition
and of the vertical velocity w in the global climate model CAM-Oslo (Abdul-Razzak and
Ghan, 2000: JGR; Storelvmo et al, 2006: JGR). In-cloud turbulence is not resolved in GCMs,
and has to be parameterized. For this, a gaussian distribution of the vertical velocity around
its grid-mean value is assumed. We test different formulations for the width Ïw of the
distribution, based on the turbulent diffusion coefficient or a turbulent velocity scale. The
simulated values are compared with observations from field campaigns and LES
simulations, amongst others from the EUCAARI-IMPACT campaign. It is found that the
spread in simulated values from different formulations is large. One parameterization
produces very large values of Ïw (>2 m/s) over land, which can be ruled out as
unrealistic under non-convective conditions. Another parameterization gives very small
values over ocean ( |
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