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| Titel |
Comprehensive assessment of meteorological conditions and airflow connectivity during HCCT-2010 |
| VerfasserIn |
A. Tilgner, L. Schöne, P. Brauer, D. van Pinxteren, E. Hoffmann, G. Spindler, S. A. Styler, S. Mertes, W. Birmili, R. Otto, M. Merkel, K. Weinhold, A. Wiedensohler, H. Deneke, R. Schrödner, R. Wolke, J. Schneider, W. Haunold, A. Engel, A. Wéber, H. Herrmann |
| 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 ; 14, no. 17 ; Nr. 14, no. 17 (2014-09-05), S.9105-9128 |
| Datensatznummer |
250119004
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| Publikation (Nr.) |
 copernicus.org/acp-14-9105-2014.pdf |
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| Zusammenfassung |
This study presents a comprehensive assessment of the meteorological
conditions and atmospheric flow during the Lagrangian-type "Hill Cap Cloud
Thuringia 2010" experiment (HCCT-2010), which was performed in September and
October 2010 at Mt. Schmücke in the Thuringian Forest, Germany and which
used observations at three measurement sites (upwind, in-cloud, and downwind)
to study physical and chemical aerosol–cloud interactions. A Lagrangian-type
hill cap cloud experiment requires not only suitable cloud conditions but
also connected airflow conditions (i.e. representative air masses at the
different measurement sites). The primary goal of the present study was to
identify time periods during the 6-week duration of the experiment in which
these conditions were fulfilled and therefore which are suitable for use in
further data examinations. The following topics were studied in detail: (i)
the general synoptic weather situations, including the mesoscale flow
conditions, (ii) local meteorological conditions and (iii) local flow
conditions. The latter were investigated by means of statistical analyses
using best-available quasi-inert tracers, SF6 tracer experiments in the
experiment area, and regional modelling. This study represents the first
application of comprehensive analyses using statistical measures such as the
coefficient of divergence (COD) and the cross-correlation in the context of a
Lagrangian-type hill cap cloud experiment. This comprehensive examination of
local flow connectivity yielded a total of 14 full-cloud events (FCEs), which
are defined as periods during which all connected flow and cloud criteria for
a suitable Lagrangian-type experiment were fulfilled, and 15 non-cloud events
(NCEs), which are defined as periods with connected flow but no cloud at the
summit site, and which can be used as reference cases. The overall evaluation
of the identified FCEs provides the basis for subsequent investigations of
the measured chemical and physical data during HCCT-2010 (see
http://www.atmos-chem-phys.net/special_issue287.html).
Results obtained from the statistical flow analyses and regional-scale
modelling performed in this study indicate the existence of a strong link
between the three measurement sites during the FCEs and NCEs,
particularly under conditions of constant southwesterly flow, high wind
speeds and slightly stable stratification. COD analyses performed using
continuous measurements of ozone and particle (49 nm diameter size bin)
concentrations at the three sites revealed, particularly for COD values
< 0.1, very consistent time series (i.e. close links between air masses
at the different sites). The regional-scale model simulations provided
support for the findings of the other flow condition analyses.
Cross-correlation analyses revealed typical overflow times of
~15–30 min between the upwind and downwind valley sites
under connected flow conditions. The results described here, together with
those obtained from the SF6 tracer experiments performed during the
experiment, clearly demonstrate that (a) under appropriate meteorological
conditions a Lagrangian-type approach is valid and (b) the connected flow
validation procedure developed in this work is suitable for identifying such
conditions. Overall, it is anticipated that the methods and tools developed
and applied in the present study will prove useful in the identification of
suitable meteorological and connected airflow conditions during future
Lagrangian-type hill cap cloud experiments. |
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