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| Titel |
Sensitivities and uncertainties of modeled ground temperatures in mountain environments |
| VerfasserIn |
S. Gubler, S. Endrizzi, S. Gruber, R. S. Purves |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 6, no. 4 ; Nr. 6, no. 4 (2013-08-23), S.1319-1336 |
| Datensatznummer |
250084979
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| Publikation (Nr.) |
 copernicus.org/gmd-6-1319-2013.pdf |
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| Zusammenfassung |
Model evaluation is often performed at few locations due to the lack of
spatially distributed data. Since the quantification of model sensitivities
and uncertainties can be performed independently from ground truth
measurements, these analyses are suitable to test the influence of
environmental variability on model evaluation. In this study, the
sensitivities and uncertainties of a physically based mountain permafrost
model are quantified within an artificial topography. The setting consists of
different elevations and exposures combined with six ground types
characterized by porosity and hydraulic properties. The analyses are
performed for a combination of all factors, that allows for quantification of the
variability of model sensitivities and uncertainties within a whole modeling
domain.
We found that model sensitivities and uncertainties vary strongly
depending on different input factors such as topography or different soil
types. The analysis shows that model evaluation performed at single locations
may not be representative for the whole modeling domain. For example, the
sensitivity of modeled mean annual ground temperature to ground albedo ranges
between 0.5 and 4 °C depending on elevation, aspect and the
ground type. South-exposed inclined locations are more sensitive to changes
in ground albedo than north-exposed slopes since they receive more solar
radiation. The sensitivity to ground albedo increases with decreasing
elevation due to shorter duration of the snow cover. The sensitivity in the
hydraulic properties changes considerably for different ground types:
rock or clay, for instance, are not sensitive to uncertainties in the hydraulic
properties, while for gravel or peat, accurate estimates of the hydraulic
properties significantly improve modeled ground temperatures. The
discretization of ground, snow and time have an impact on modeled mean
annual ground temperature (MAGT) that
cannot be neglected (more than 1 °C for several discretization
parameters). We show that the temporal resolution should be at least 1 h
to ensure errors less than 0.2 °C in modeled MAGT, and the
uppermost ground layer should at most be 20 mm thick.
Within the topographic setting, the total parametric output uncertainties
expressed as the length of the 95% uncertainty interval of the Monte Carlo
simulations range from 0.5 to 1.5 °C for clay and silt, and
ranges from 0.5 to around 2.4 °C for peat, sand, gravel and
rock. These uncertainties are comparable to the variability of ground surface
temperatures measured within 10 m × 10 m grids in Switzerland. The
increased uncertainties for sand, peat and gravel are largely due to their
sensitivity to the hydraulic conductivity. |
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