 |
| Titel |
Investigation of the effective peak supersaturation for liquid-phase clouds at the high-alpine site Jungfraujoch, Switzerland (3580 m a.s.l.) |
| VerfasserIn |
E. Hammer, N. Bukowiecki, M. Gysel, Z. Jurányi, C. R. Hoyle, R. Vogt, U. Baltensperger, E. Weingärtner |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 2 ; Nr. 14, no. 2 (2014-01-29), S.1123-1139 |
| Datensatznummer |
250118326
|
| Publikation (Nr.) |
 copernicus.org/acp-14-1123-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Aerosols influence the Earth's radiation budget directly through
absorption and scattering of solar radiation in the atmosphere but
also indirectly by modifying the properties of clouds. However,
climate models still suffer from large uncertainties as a result of
insufficient understanding of aerosol-cloud interactions. At the
high altitude research station Jungfraujoch (JFJ;
3580 m a.s.l., Switzerland) cloud condensation nuclei (CCN)
number concentrations at eight different supersaturations (SS) from
0.24% to 1.18% were measured using a CCN counter during
Summer 2011. Simultaneously, in-situ aerosol activation properties
of the prevailing ambient clouds were investigated by measuring the
total and interstitial (non-activated) dry particle number size
distributions behind two different inlet systems. Combining all
experimental data, a new method was developed to retrieve the
so-called effective peak supersaturation SSpeak,
as a measure of the SS at which ambient clouds are
formed. A 17-month CCN climatology was then used to retrieve the
SSpeak values also for four earlier summer
campaigns (2000, 2002, 2004 and 2010) where no direct CCN data were
available. The SSpeak values varied between
0.01% and 2.0% during all campaigns. An overall median
SSpeak of 0.35% and dry activation diameter
of 87 nm was observed. It was found that the difference in
topography between northwest and southeast plays an important role
for the effective peak supersaturation in clouds formed in the
vicinity of the JFJ, while differences in the number concentration
of potential CCN only play a minor role. Results show that air
masses coming from the southeast (with the slowly rising terrain of
the Aletsch Glacier) generally experience lower
SSpeak values than air masses coming from the
northwest (steep slope). The observed overall median values were
0.41% and 0.22% for northwest and southeast wind
conditions, respectively, corresponding to literature values for
cumulus clouds and shallow-layer clouds. These cloud types are
consistent with weather observations routinely performed at the JFJ. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|