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| Titel |
Potential impacts from biological aerosols on ensembles of continental clouds simulated numerically |
| VerfasserIn |
V. T. J. Phillips, C. Andronache, B. Christner, C. E. Morris, D. C. Sands, A. Bansemer, A. Lauer, C. McNaughton, C. Seman |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 6, no. 6 ; Nr. 6, no. 6 (2009-06-12), S.987-1014 |
| Datensatznummer |
250003835
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| Publikation (Nr.) |
 copernicus.org/bg-6-987-2009.pdf |
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| Zusammenfassung |
An aerosol-cloud modeling framework is described to simulate the activation
of ice particles and droplets by biological aerosol particles, such as
airborne ice-nucleation active (INA) bacteria. It includes the empirical
parameterisation of heterogeneous ice nucleation and a semi-prognostic
aerosol component, which have been incorporated into a cloud-system resolving
model (CSRM) with double-moment bulk microphysics. The formation of cloud
liquid by soluble material coated on these partially insoluble organic
aerosols is represented. It determines their partial removal from deep
convective clouds by accretion onto precipitation in the cloud model. This
"aerosol-cloud model" is validated for diverse cases of deep convection
with contrasting aerosol conditions, against satellite, ground-based and
aircraft observations.
Simulations are performed with the aerosol-cloud model for a month-long
period of summertime convective activity over Oklahoma. It includes three
cases of continental deep convection simulated previously by Phillips and
Donner (2006). Elevated concentrations of insoluble organic aerosol, boosted
by a factor of 100 beyond their usual values for this continental region, are
found to influence significantly the following quantities: (1) the average
numbers and sizes of ice crystals and droplets in the clouds; (2) the
horizontal cloud coverage in the free troposphere; (3) precipitation at the
ground; and (4) incident solar insolation at the surface. This factor of 100
is plausible for natural fluctuations of the concentration of insoluble
organic aerosol, in view of variability of cell concentrations for airborne
bacteria seen by Lindemann et al. (1982).
In nature, such boosting of the insoluble organic aerosol loading could arise
from enhanced emissions of biological aerosol particles from a land surface.
Surface wetness and solar insolation at the ground are meteorological
quantities known to influence rates of growth of certain biological particles
(e.g. bacteria). Their rates of emission into the atmosphere must depend on
these same quantities, in addition to surface wind speed, turbulence and
convection. Finally, the present study is the first attempt at evaluating the
impacts from biological aerosols on mesoscale cloud ensembles in the
literature. |
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