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| Titel |
Aircraft observations of cold pools under marine stratocumulus |
| VerfasserIn |
C. R. Terai, R. Wood |
| 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 ; 13, no. 19 ; Nr. 13, no. 19 (2013-10-08), S.9899-9914 |
| Datensatznummer |
250085737
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| Publikation (Nr.) |
 copernicus.org/acp-13-9899-2013.pdf |
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| Zusammenfassung |
| Although typically associated with precipitating cumuli, cold pools
also form under shallower stratocumulus. This study presents cold-pool
observations as sampled by the NSF/NCAR C-130, which made cloud
and boundary-layer measurements over the southeast Pacific
stratocumulus region at an altitude of approximately 150 m
during the VOCALS Regional Experiment. Ninety edges of cold pools are
found in the C-130 measurements by identifying step-like changes in
the potential temperature. Examination of their mesoscale environment
shows that the observed cold pools tend to form under heavier
precipitation, thicker clouds, and in cleaner environments. Cold pools
are also found to form under clouds with high LWP values over the
night of or before sampling. When they form, cold pools often form in
clusters or on top of each other, rather than as separate, individual
entities. Their sizes range from 2 km to 16 km (middle
50th percentile), where the largest of cold pools are associated with
the greatest drops in temperature. Composites of various observed
thermodynamic and chemical variables along the cold-pool edges
indicate increased humidity, equivalent potential temperature,
coarse-mode aerosol, and dimethyl sulfide concentration inside cold
pools. The enhancements inside cold pools are consistent with
increased static stability that traps fluxes from the ocean surface in
the lowest levels of the boundary layer. By using pressure
perturbations, the average cold pool is estimated to be approximately
300 m deep. The temperature depression in cold pools also leads to
density-driven flows that drive convergence of horizontal winds and
measurable, mechanically driven vertical wind velocity at the edges of
cold pools. |
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