 |
| Titel |
Numerical simulations of homogeneous freezing processes in the aerosol chamber AIDA |
| VerfasserIn |
W. Haag, B. Kärcher, S. Schaefers, O. Stetzer, O. Möhler, U. Schurath, M. Krämer, C. Schiller |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 3, no. 1 ; Nr. 3, no. 1 (2003-02-20), S.195-210 |
| Datensatznummer |
250000719
|
| Publikation (Nr.) |
 copernicus.org/acp-3-195-2003.pdf |
|
|
|
|
|
| Zusammenfassung |
| The homogeneous freezing of supercooled
H2SO4/H2O aerosols in an aerosol chamber is investigated with a
microphysical box model using the activity parameterization of the nucleation rate by
Koop et al. (2000). The simulations are constrained by measurements of pressure, temperature, total water mixing
ratio, and the initial aerosol size distribution, described in a companion paper
Möhler et al. (2003). Model results are compared to measurements conducted in the temperature range between
194 and 235 K, with cooling rates in the range between 0.5 and 2.6 K min-1, and at air pressures between
170 and 1000 hPa. The simulations focus on the time history of relative humidity with respect to ice, aerosol size distribution,
partitioning of water between gas and particle phase, onset times of freezing, freezing threshold relative
humidities, aerosol chemical composition at the onset of freezing, and the number of
nucleated ice crystals. The latter four parameters can be inferred from the experiments, the former three aid in interpreting the
measurements. Sensitivity studies are carried out to address the relative importance of uncertainties of basic quantities such as
temperature, total H2O
mixing ratio, aerosol size spectrum, and deposition coefficient of H2O
molecules on ice. The ability of the numerical simulations to provide detailed
explanations of the observations greatly increases confidence in attempts to model this process under real atmospheric conditions,
for instance with regard to the formation of cirrus clouds or polar stratospheric ice clouds, provided that accurate temperature
and humidity measurements are available. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|