 |
| Titel |
13-month climatology of the aerosol hygroscopicity at the free tropospheric site Jungfraujoch (3580 m a.s.l.) |
| VerfasserIn |
L. Kammermann, M. Gysel, E. Weingärtner, U. Baltensperger |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 22 ; Nr. 10, no. 22 (2010-11-16), S.10717-10732 |
| Datensatznummer |
250008891
|
| Publikation (Nr.) |
 copernicus.org/acp-10-10717-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
A hygroscopicity tandem differential mobility analyzer (HTDMA) was operated
at the high-alpine site Jungfraujoch in order to characterize the hygroscopic
diameter growth factors of the free tropospheric Aitken and accumulation mode
aerosol. More than ~5000 h of valid data were collected for the dry
diameters D0 = 35, 50, 75, 110, 165, and 265 nm during the 13-month
measurement period from 1 May 2008 through 31 May 2009. No distinct seasonal
variability of the hygroscopic properties was observed. Annual mean
hygroscopic diameter growth factors (D/D0) at 90% relative humidity were
found to be 1.34, 1.43, and 1.46 for D0 = 50, 110, and 265 nm,
respectively. This size dependence can largely be attributed to the Kelvin
effect because corresponding values of the hygroscopicity parameter κ
are nearly independent of size. The mean hygroscopicity of the Aitken and
accumulation mode aerosol at the free tropospheric site Jungfraujoch was
found to be κ≈0.24 with little variability throughout the
year.
The impact of Saharan dust events, a frequent phenomenon at the Jungfraujoch,
on aerosol hygroscopicity was shown to be negligible for D0<265 nm.
Thermally driven injections of planetary boundary layer (PBL) air,
particularly observed in the early afternoon of summer days with convective
anticyclonic weather conditions, lead to a decrease of aerosol
hygroscopicity. However, the effect of PBL influence is not seen in the
annual mean hygroscopicity data because the effect is small and those
conditions (weather class, season and time of day) with PBL influence are
relatively rare.
Aerosol hygroscopicity was found to be virtually independent of synoptic wind
direction during advective weather situations, i.e. when horizontal motion
of the atmosphere dominates over thermally driven convection. This indicates
that the hygroscopic behavior of the aerosol observed at the Jungfraujoch can
be considered representative of the lower free troposphere on at least
a regional if not continental scale. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|