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| Titel |
Observations and comparisons of cloud microphysical properties in spring and summertime Arctic stratocumulus clouds during the ACCACIA campaign |
| VerfasserIn |
G. Lloyd, T. W. Choularton, K. N. Bower, J. Crosier, H. Jones, J. R. Dorsey, M. W. Gallagher, P. Connolly, A. C. R. Kirchgaessner, T. Lachlan-Cope |
| 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 ; 15, no. 7 ; Nr. 15, no. 7 (2015-04-02), S.3719-3737 |
| Datensatznummer |
250119615
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| Publikation (Nr.) |
 copernicus.org/acp-15-3719-2015.pdf |
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| Zusammenfassung |
| Measurements from four case studies in spring and summer-time Arctic
stratocumulus clouds during the Aerosol-Cloud Coupling And Climate
Interactions in the Arctic (ACCACIA) campaign are presented. We compare
microphysics observations between cases and with previous measurements made
in the Arctic and Antarctic. During ACCACIA, stratocumulus clouds were
observed to consist of liquid at cloud tops, often at distinct temperature
inversions. The cloud top regions precipitated low concentrations of ice
into the cloud below. During the spring cases median ice number
concentrations (~ 0.5 L−1) were found to be lower by
about a factor of 5 than observations from the summer campaign
(~ 3 L−1). Cloud layers in the summer spanned a warmer
temperature regime than in the spring and enhancement of ice concentrations
in these cases was found to be due to secondary ice production through the
Hallett–Mossop (H–M) process. Aerosol concentrations during spring ranged
from ~ 300–400 cm−3 in one case to lower values of
~ 50–100 cm−3 in the other. The concentration of aerosol
with sizes Dp > 0.5 μm was used in a primary ice
nucleus (IN) prediction scheme (DeMott et al., 2010). Predicted IN values
varied depending on aerosol measurement periods but were generally greater
than maximum observed median values of ice crystal concentrations in the
spring cases, and less than the observed ice concentrations in the summer
due to the influence of secondary ice production. Comparison with recent
cloud observations in the Antarctic summer (Grosvenor et al., 2012), reveals
lower ice concentrations in Antarctic clouds in comparable seasons. An
enhancement of ice crystal number concentrations (when compared with
predicted IN numbers) was also found in Antarctic stratocumulus clouds
spanning the H–M temperature zone; however, concentrations were
about an order of magnitude lower than those observed in the Arctic summer
cases but were similar to the peak values observed in the colder Arctic
spring cases, where the H–M mechanism did not operate. |
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