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| Titel |
Measured and modelled sublimation on the tropical Glaciar Artesonraju, Perú |
| VerfasserIn |
M. Winkler, I. Juen, T. Mölg, P. Wagnon, J. Gómez, G. Kaser  |
| 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. 1 ; Nr. 3, no. 1 (2009-02-09), S.21-30 |
| Datensatznummer |
250000782
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| Publikation (Nr.) |
 copernicus.org/tc-3-21-2009.pdf |
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| Zusammenfassung |
Sublimation plays a decisive role in the surface energy and mass balance of
tropical glaciers. During the dry season (May–September) low specific
humidity and high surface roughness favour the direct transition from ice to
vapour and drastically reduce the energy available for melting. However,
field measurements are scarce and little is known about the performance of
sublimation parameterisations in glacier mass balance and runoff models.
During 15 days in August 2005 sublimation was measured on the tongue of
Glaciar Artesonraju (8°58' S, 77°38' W) in the Cordillera
Blanca, Perú, using simple lysimeters. Indicating a strong dependence on
surface roughness, daily totals of sublimation range from 1–3 kg m−2
for smooth to 2–5 kg m−2 for rough conditions. (The 15-day means at
that time of wind speed and specific humidity were 4.3 m s−1 and
3.8 g kg−1, respectively.)
Measured sublimation was related to characteristic surface roughness lengths
for momentum (zm) and for the scalar quantities of temperature and water
vapour (zs), using a process-based mass balance model. Input data were
provided by automatic weather stations, situated on the glacier tongue at
4750 m a.s.l. and 4810 m a.s.l., respectively. Under smooth conditions the
combination zm=2.0 mm and zs=1.0 mm appeared to be most
appropriate, for rough conditions zm=20.0 mm and zs=10.0 mm
fitted best.
Extending the sublimation record from April 2004 to December 2005 with the
process-based model confirms, that sublimation shows a clear seasonality.
60–90% of the energy available for ablation is consumed by sublimation in
the dry season, but only 10–15% in the wet season (October–April). The
findings are finally used to evaluate the parameterisation of sublimation in
the lower-complexity mass balance model ITGG, which has the advantage of
requiring precipitation and air temperature as only input data. It turns out
that the implementation of mean wind speed is a possible improvement for the
representation of sublimation in the ITGG model. |
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