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| Titel |
Climatology of cloud (radiative) parameters at two stations in Switzerland using hemispherical sky-cameras |
| VerfasserIn |
Christine Aebi, Julian Gröbner, Niklaus Kämpfer, Laurent Vuilleumier |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250149623
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| Publikation (Nr.) |
 EGU/EGU2017-13990.pdf |
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| Zusammenfassung |
| Our study analyses climatologies of cloud fraction, cloud type and cloud radiative effect
depending on different parameters at two stations in Switzerland. The calculations have been
performed for shortwave (0.3 – 3 μm) and longwave (3 – 100 μm) radiation
separately. Information about fractional cloud coverage and cloud type is automatically
retrieved from images taken by visible all-sky cameras at the two stations Payerne
(490 m asl) and Davos (1594 m asl) using a cloud detection algorithm developed by
PMOD/WRC (Wacker et al., 2015). Radiation data are retrieved from pyranometers and
pyrgeometers, the cloud base height from a ceilometer and IWV data from GPS
measurements.
Interestingly, Davos and Payerne show different trends in terms of cloud coverage and
cloud fraction regarding seasonal variations. The absolute longwave cloud radiative effect
(LCE) for low-level clouds and a cloud coverage of 8 octas has a median value
between 61 and 72 Wm−2. It is shown that the fractional cloud coverage, the cloud
base height (CBH) and integrated water vapour (IWV) all have an influence on
the magnitude of the LCE and will be illustrated with key examples. The relative
values of the shortwave cloud radiative effect (SCE) for low-level clouds and a cloud
coverage of 8 octas are between -88 to -62 %. The SCE is also influenced by the
latter parameters, but also if the sun is covered or not by clouds. At both stations
situations of shortwave radiation cloud enhancements have been observed and will be
discussed.
Wacker S., J. Gröbner, C. Zysset, L. Diener, P. Tzoumanikas, A. Kazantzidis, L.
Vuilleumier, R. Stöckli, S. Nyeki, and N. Kämpfer (2015) Cloud observations in
Switzerland using hemispherical sky cameras, J. Geophys. Res. Atmos, 120, 695-707. |
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