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| Titel |
The annual surface energy budget of a high-arctic permafrost site on Svalbard, Norway |
| VerfasserIn |
S. Westermann, J. Lüers, M. Langer, K. Piel, J. Boike |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 3, no. 2 ; Nr. 3, no. 2 (2009-12-18), S.245-263 |
| Datensatznummer |
250000941
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| Publikation (Nr.) |
 copernicus.org/tc-3-245-2009.pdf |
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| Zusammenfassung |
Independent measurements of radiation, sensible and latent heat fluxes and
the ground heat flux are used to describe the annual cycle of the surface
energy budget at a high-arctic permafrost site on Svalbard. During summer,
the net short-wave radiation is the dominant energy source, while well
developed turbulent processes and the heat flux in the ground lead to a
cooling of the surface. About 15% of the net radiation is consumed by
the seasonal thawing of the active layer in July and August. The Bowen ratio
is found to vary between 0.25 and 2, depending on water content of the
uppermost soil layer. During the polar night in winter, the net long-wave
radiation is the dominant energy loss channel for the surface, which is
mainly compensated by the sensible heat flux and, to a lesser extent, by the
ground heat flux, which originates from the refreezing of the active layer.
The average annual sensible heat flux of −6.9 Wm−2 is composed
of strong positive fluxes in July and August, while negative fluxes dominate
during the rest of the year. With 6.8 Wm−2, the latent heat flux
more or less compensates the sensible heat flux in the annual average. Strong
evaporation occurs during the snow melt period and particularly during the
snow-free period in summer and fall. When the ground is covered by snow,
latent heat fluxes through sublimation of snow are recorded, but are
insignificant for the average surface energy budget. The near-surface
atmospheric stratification is found to be predominantly unstable to neutral,
when the ground is snow-free, and stable to neutral for snow-covered ground.
Due to long-lasting near-surface inversions in winter, an average temperature
difference of approximately 3 K exists between the air temperature at
10 m height and the surface temperature of the snow.
As such comprehensive data sets are sparse for the Arctic, they are of great
value to improve process understanding and support modeling efforts on the
present-day and future arctic climate and permafrost conditions. |
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