 |
| Titel |
Effects of pre-existing ice crystals on cirrus clouds and comparison between different ice nucleation parameterizations with the Community Atmosphere Model (CAM5) |
| VerfasserIn |
X. Shi, X. Liu, K. Zhang |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 3 ; Nr. 15, no. 3 (2015-02-11), S.1503-1520 |
| Datensatznummer |
250119405
|
| Publikation (Nr.) |
 copernicus.org/acp-15-1503-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
In order to improve the treatment of ice nucleation in a more realistic
manner in the Community Atmosphere Model version 5.3 (CAM5.3), the effects
of pre-existing ice crystals on ice nucleation in cirrus clouds are
considered. In addition, by considering the in-cloud variability in ice
saturation ratio, homogeneous nucleation takes place spatially only in a
portion of the cirrus cloud rather than in the whole area of the cirrus cloud.
Compared to observations, the ice number concentrations and the probability
distributions of ice number concentration are both improved with the updated
treatment. The pre-existing ice crystals significantly reduce ice number
concentrations in cirrus clouds, especially at mid- to high latitudes in the
upper troposphere (by a factor of ~10). Furthermore, the
contribution of heterogeneous ice nucleation to cirrus ice crystal number
increases considerably.
Besides the default ice nucleation parameterization of Liu and Penner (2005,
hereafter LP) in CAM5.3, two other ice nucleation parameterizations of
Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006,
hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice
crystal number concentration, percentage contribution from heterogeneous ice
nucleation to total ice crystal number, and pre-existing ice effects
simulated by the three ice nucleation parameterizations have similar
patterns in the simulations with present-day aerosol emissions. However, the
change (present-day minus pre-industrial times) in global annual mean column
ice number concentration from the KL parameterization
(3.24 × 106 m−2) is less than that from the LP (8.46 × 106 m−2)
and BN (5.62 × 106 m−2) parameterizations. As a
result, the experiment using the KL parameterization predicts a much smaller
anthropogenic aerosol long-wave indirect forcing (0.24 W m−2) than that
using the LP (0.46 W m−2) and BN (0.39 W m−2) parameterizations. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|