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| Titel |
Reallocation in modal aerosol models: impacts on predicting aerosol radiative effects |
| VerfasserIn |
T. Korhola, H. Kokkola, H. Korhonen, A.-I. Partanen, A. Laaksonen, K. E. J. Lehtinen, S. Romakkaniemi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 7, no. 1 ; Nr. 7, no. 1 (2014-01-28), S.161-174 |
| Datensatznummer |
250115535
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| Publikation (Nr.) |
 copernicus.org/gmd-7-161-2014.pdf |
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| Zusammenfassung |
| Atmospheric models often represent the aerosol particle size distribution
with a modal approach, in which particles are described with log-normal
modes within predetermined size ranges. This approach reallocates particles
numerically from one mode to another for example during particle growth,
potentially leading to artificial changes in the aerosol size distribution.
In this study we analysed how the modal reallocation affects
climate-relevant variables: cloud droplet number concentration (CDNC),
aerosol–cloud interaction parameter (ACI) and light extinction coefficient
(qext). The ACI parameter gives the response of CDNC to a change in
total aerosol number concentration. We compared these variables between a
modal model (with and without reallocation routines) and a high resolution
sectional model, which was considered a reference model. We analysed the
relative differences in the chosen variables in four experiments designed to
assess the influence of atmospheric aerosol processes. We find that limiting
the allowed size ranges of the modes, and subsequent remapping of the
distribution, leads almost always to an underestimation of cloud droplet
number concentrations (by up to 100%) and an overestimation of light
extinction (by up to 20%). On the other hand, the aerosol–cloud
interaction parameter can be either over- or underestimated by the
reallocating model, depending on the conditions. For example, in the case of
atmospheric new particle formation events followed by rapid particle growth,
the reallocation can cause on average a 10% overestimation of the ACI
parameter. Thus it is shown that the reallocation affects the ability of a
model to estimate aerosol climate effects accurately, and this should be
taken into account when using and developing aerosol models. |
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