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| Titel |
Importance of including ammonium sulfate ((NH4)2SO4) aerosols for ice cloud parameterization in GCMs |
| VerfasserIn |
P. S. Bhattacharjee, Y. C. Sud, X. Liu, G. K. Walker, R. Yang, J. Wang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 28, no. 2 ; Nr. 28, no. 2 (2010-02-22), S.621-631 |
| Datensatznummer |
250016789
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| Publikation (Nr.) |
 copernicus.org/angeo-28-621-2010.pdf |
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| Zusammenfassung |
| A common deficiency of many cloud-physics parameterizations including the
NASA's microphysics of clouds with aerosol-cloud interactions (hereafter
called McRAS-AC) is that they simulate lesser (larger) than the observed ice
cloud particle number (size). A single column model (SCM) of McRAS-AC
physics of the GEOS4 Global Circulation Model (GCM) together with an
adiabatic parcel model (APM) for ice-cloud nucleation (IN) of aerosols were
used to systematically examine the influence of introducing ammonium sulfate
(NH4)2SO4 aerosols in McRAS-AC and its influence on the
optical properties of both liquid and ice clouds. First an
(NH4)2SO4 parameterization was included in the APM to assess
its effect on clouds vis-à-vis that of the other aerosols. Subsequently,
several evaluation tests were conducted over the ARM Southern Great Plain
(SGP) and thirteen other locations (sorted into pristine and polluted
conditions) distributed over marine and continental sites with the SCM. The
statistics of the simulated cloud climatology were evaluated against the
available ground and satellite data. The results showed that inclusion of
(NH4)2SO4 into McRAS-AC of the SCM made a remarkable
improvement in the simulated effective radius of ice cloud particulates.
However, the corresponding ice-cloud optical thickness increased even more
than the observed. This can be caused by lack of horizontal cloud advection
not performed in the SCM. Adjusting the other tunable parameters such as
precipitation efficiency can mitigate this deficiency. Inclusion of ice
cloud particle splintering invoked empirically further reduced simulation
biases. Overall, these changes make a substantial improvement in simulated
cloud optical properties and cloud distribution particularly over the
Intertropical Convergence Zone (ITCZ) in the GCM. |
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