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| Titel |
Observations of the boundary layer, cloud, and aerosol variability in the southeast Pacific near-coastal marine stratocumulus during VOCALS-REx |
| VerfasserIn |
X. Zheng, B. Albrecht, H. H. Jonsson, D. Khelif, G. Feingold, P. Minnis, K. Ayers, P. Chuang, S. Donaher, D. Rossiter, V. Ghate, J. Ruiz-Plancarte, S. Sun-Mack |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 18 ; Nr. 11, no. 18 (2011-09-27), S.9943-9959 |
| Datensatznummer |
250010105
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| Publikation (Nr.) |
 copernicus.org/acp-11-9943-2011.pdf |
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| Zusammenfassung |
| Aircraft observations made off the coast of northern Chile in the
Southeastern Pacific (20° S, 72° W; named Point Alpha) from 16 October
to 13 November 2008 during the VAMOS Ocean-Cloud- Atmosphere-Land
Study-Regional Experiment (VOCALS-REx), combined with meteorological
reanalysis, satellite measurements, and radiosonde data, are used to
investigate the boundary layer (BL) and aerosol-cloud-drizzle variations in
this region. On days without predominately synoptic and meso-scale
influences, the BL at Point Alpha was typical of a non-drizzling
stratocumulus-topped BL. Entrainment rates calculated from the near
cloud-top fluxes and turbulence in the BL at Point Alpha appeared to be
weaker than those in the BL over the open ocean west of Point Alpha and the
BL near the coast of the northeast Pacific. The cloud liquid water path
(LWP) varied between 15 g m−2 and 160 g m−2. The BL had a depth of
1140 ± 120 m, was generally well-mixed and capped by a sharp inversion
without predominately synoptic and meso-scale influences. The wind direction
generally switched from southerly within the BL to northerly above the
inversion. On days when a synoptic system and related mesoscale costal
circulations affected conditions at Point Alpha (29 October–4 November), a moist
layer above the inversion moved over Point Alpha, and the total-water mixing
ratio above the inversion was larger than that within the BL.
The accumulation mode aerosol varied from 250 to 700 cm−3 within the
BL, and CCN at 0.2 % supersaturation within the BL ranged between 150 and
550 cm−3. The main aerosol source at Point Alpha was horizontal
advection within the BL from south. The average cloud droplet number
concentration ranged between 80 and 400 cm−3. While the mean LWP
retrieved from GOES was in good agreement with the in situ measurements, the
GOES-derived cloud droplet effective radius tended to be larger than that
from the aircraft in situ observations near cloud top. The aerosol and cloud LWP
relationship reveals that during the typical well-mixed BL days the cloud
LWP increased with the CCN concentrations. On the other hand, meteorological
factors and the decoupling processes have large influences on the cloud LWP
variation as well. |
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