 |
| Titel |
A simplified treatment of surfactant effects on cloud drop activation |
| VerfasserIn |
T. Raatikainen, A. Laaksonen |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1991-959X
|
| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 4, no. 1 ; Nr. 4, no. 1 (2011-02-28), S.107-116 |
| Datensatznummer |
250001556
|
| Publikation (Nr.) |
 copernicus.org/gmd-4-107-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
Dissolved surface active species, or surfactants, have a tendency to
partition to solution surface and thereby decrease solution surface tension.
Activating cloud droplets have large surface-to-volume ratios, and the amount
of surfactant molecules in them is limited. Therefore, unlike with
macroscopic solutions, partitioning to the surface can effectively deplete
the droplet interior of surfactant molecules.
Surfactant partitioning equilibrium for activating cloud droplets has so far
been solved numerically from a group of non-linear equations containing the
Gibbs adsorption equation coupled with a surface tension model and an
optional activity coefficient model. This can be a problem when surfactant
effects are examined by using large-scale cloud models. Namely, computing
time increases significantly due to the partitioning calculations done in the
lowest levels of nested iterations.
Our purpose is to reduce the group of non-linear equations to simple
polynomial equations with well known analytical solutions. In order to do
that, we describe surface tension lowering using the Szyskowski equation, and
ignore all droplet solution non-idealities. It is assumed that there is only
one surfactant exhibiting bulk-surface partitioning, but the number of
non-surfactant solutes is unlimited. It is shown that the simplifications
cause only minor errors to predicted bulk solution concentrations and cloud
droplet activation. In addition, computing time is decreased at least by an
order of magnitude when using the analytical solutions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|