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| Titel |
Effects of local microclimates on the surface sensible heat flux on a mid-latitude alpine valley glacier using Large-Eddy Simulations |
| VerfasserIn |
Tobias Sauter, Stephan Galos |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127423
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| Publikation (Nr.) |
 EGU/EGU2016-7300.pdf |
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| Zusammenfassung |
| While the large-scale climate conditions play an important role in shaping the environment in
which glaciers exist, the mass and energy balance of each individual glacier are dictated by
local conditions. Given the complex mountain topography around alpine glaciers, it is not
trivial to find a direct link between the large-scale atmospheric motions and the local-scale
weather conditions at an individual glacier. Non-local dynamic effects due to the surrounding
complex topography can significantly modify the spatial variability of exchange processes,
either by small scale circulations or episodic entrainment of heat and momentum by burst
events.
Motivated by the fact that distributed glacier models strongly rely on the quality of high
resolution forcing data to adequately represent the glacier wide ablation and accumulation
processes, the present study investigates (i) whether non-local topographic effects
have a significant impact on the spatial distribution of turbulent sensible heat fluxes
(local microclimates) over alpine glaciers, and (ii) how much variability is smoothed
out when using linearly interpolated fields together with the commonly used bulk
approach. To answer these questions, we perform highly resolved and properly
designed case experiments by Large-Eddy Simulations with real topography to
determine the impact of topographic flow features on the spatial variability of the
surface sensible heat flux and compare the fields with those derived with the bulk
approach.
The analysis shows that there is a significant spatial variability of the mean fluxes with values
ranging from -10 Wm−2 to -120 Wm−2. Since the sensible heat flux can make up to
40% of the total melting on mid-latitude alpine valley glaciers, the heterogeneity of
the fluxes can substantially dictate the local melting rates. When estimating the
glacier-wide surface heat fluxes on the basis of point-measurements and the bulk
approach, a considerable amount of spatial information is lost. All together, the bulk
approach underestimates the average glacier-wide sensible heat flux by more than
20%, which might lead to great uncertainties in the calculated glacier-wide ablation
rates. |
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