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| Titel |
Formulation and test of an ice aggregation scheme for two-moment bulk microphysics schemes |
| VerfasserIn |
E. Kienast-Sjögren, P. Spichtinger, K. Gierens |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 17 ; Nr. 13, no. 17 (2013-09-09), S.9021-9037 |
| Datensatznummer |
250085684
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| Publikation (Nr.) |
 copernicus.org/acp-13-9021-2013.pdf |
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| Zusammenfassung |
| A simple formulation of aggregation for two-moment bulk microphysical
models is derived. The solution involves the evaluation of a double
integral of the collection kernel weighted with the crystal size (or
mass) distribution. This quantity is to be inserted into the
differential equation for the crystal number concentration which has
classical Smoluchowski form. The double integrals are evaluated
numerically for log-normal size distributions over a large range of
geometric mean masses. A polynomial fit of the results is given that
yields good accuracy. Various tests of the new parameterisation are
described: aggregation as stand-alone process, in a box-model, and
in 2-D simulations of a cirrostratus cloud. These tests suggest that
aggregation can become important for warm cirrus, leading even to
higher and longer-lasting in-cloud supersaturation. Cold cirrus
clouds are hardly affected by aggregation. The collection efficiency
is taken from a parameterisation that assumes a dependence on
temperature, a situation that might be improved when reliable
measurements from cloud chambers suggests the necessary constraints
for the choice of this parameter. |
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