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| Titel |
Meteorological conditions in the central Arctic summer during the Arctic Summer Cloud Ocean Study (ASCOS) |
| VerfasserIn |
M. Tjernström, C. E. Birch, I. M. Brooks, M. D. Shupe, P. O. G. Persson, J. Sedlar, T. Mauritsen, C. Leck, J. Paatero, M. Szczodrak, C. R. Wheeler |
| 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 ; 12, no. 15 ; Nr. 12, no. 15 (2012-08-01), S.6863-6889 |
| Datensatznummer |
250011360
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| Publikation (Nr.) |
 copernicus.org/acp-12-6863-2012.pdf |
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| Zusammenfassung |
Understanding the rapidly changing climate in the Arctic is limited by a
lack of understanding of underlying strong feedback mechanisms that are
specific to the Arctic. Progress in this field can only be obtained by
process-level observations; this is the motivation for intensive
ice-breaker-based campaigns such as the Arctic Summer Cloud-Ocean Study
(ASCOS), described here. However, detailed field observations also have to
be put in the context of the larger-scale meteorology, and short field
campaigns have to be analysed within the context of the underlying climate
state and temporal anomalies from this.
To aid in the analysis of other parameters or processes observed during this
campaign, this paper provides an overview of the synoptic-scale meteorology
and its climatic anomaly during the ASCOS field deployment. It also provides
a statistical analysis of key features during the campaign, such as key
meteorological variables, the vertical structure of the lower troposphere
and clouds, and energy fluxes at the surface. In order to assess the
representativity of the ASCOS results, we also compare these features to
similar observations obtained during three earlier summer experiments in the
Arctic Ocean: the AOE-96, SHEBA and AOE-2001 expeditions.
We find that these expeditions share many key features of the summertime
lower troposphere. Taking ASCOS and the previous expeditions together, a
common picture emerges with a large amount of low-level cloud in a
well-mixed shallow boundary layer, capped by a weak to moderately strong
inversion where moisture, and sometimes also cloud top, penetrate into the
lower parts of the inversion. Much of the boundary-layer mixing is due to
cloud-top cooling and subsequent buoyant overturning of the cloud. The cloud
layer may, or may not, be connected with surface processes depending on the
depths of the cloud and surface-based boundary layers and on the relative
strengths of surface-shear and cloud-generated turbulence. The latter also
implies a connection between the cloud layer and the free troposphere
through entrainment at cloud top. |
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