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| Titel |
Inluence of snow cover on MAGST over complex morphologies |
| VerfasserIn |
Paolo Pogliotti, Stephan Gruber, Marco Giardino, Matteo Dall'Amico, Edoardo Cremonese, Umberto Morra di Cella |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250050263
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| Zusammenfassung |
| Snow cover affects ground temperatures by increasing albedo, consuming melt energy and
insulating the ground surface from cold atmospheric conditions. However such insulating
effect is a non-linear function of the snow depth. Several studies show that thin snow covers
promote cooling effect until a critical thickness above which a warming effect occur. In
high-mountain regions, snow cover distribution and thickness are strongly variable within
few tens of meters. While low slope angles promote thick snow cover, the snow
depth in steep bedrock is usually shallower but also spatially more variable and
intermittent. Consequently, it is hypothesized that the cooling effect is largest in
medium-steep terrain and it diminishes towards both vertical rock walls, because of
the absence of snow cover and more gentle terrain, which promotes thick snow
cover.
In this work these hypotheses are verified performing a series of idealized 1D experiments
using the hydrological model GEOtop. The experimental design is based on the
comparison between the MAGST of one dry simulation without snow and the MAGST
of many wet simulations, describing different scenarios of snow accumulation.
The topographic complexity of high-mountain regions is summarized by a list of
simulation points covering diverse aspects (0-360°N), slope angles (0-90°) and elevations
(2000-4000 m). Two enforced correction of the snow depth are used for creating
the many different conditions of snow amount over each simulation point. Such
corrections are based on (i) the limitation of the maximum snow water equivalent
admitted over the point and (ii) a reduction of the snow depth in function of the slope
angle.
The experimental design developed has proved successful. The initial hypothesis have been
confirmed and the variability of cooling/warming effect of snow on MAGST described. The
mean annual snow depth (MASD) admitted before the warming of MAGST takes place, is
spatially variable due to changes in snow density and related thermal conduction properties.
Such amount of snow is higher on gentle morphologies (below 30-40°) and southern aspects,
while strongly decreases towards steep slopes and shaded quadrants. Regardless the
topography all the conditions which promotes the onset of a thin MASD promotes the cooling
of MAGST. Consequently the cooling can potentially occur everywhere. On the other hand
the warming effect can occur only on gentle terrain, which promotes thick snow cover. At
higher elevation the intensity of both cooling (with thin snow) and warming (with
thick snow) is enhanced as a consequence of the higher temperature difference
between MAGST and mean annual air temperature (MAAT). In the experimental
conditions adopted, the maximum intensity of cooling and warming due to snow ranges
within 2-3 [°C]. The methods, assumption and limits of the work will be discussed. |
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