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| Titel |
Analysis of a 4 year record of meteorological data and energy and mass balance of Forni Glacier, Ortles-Cevedale Group (Stelvio National Park, Italian Alps) |
| VerfasserIn |
Antonella Senese, Guglielmina Diolaiuti, Claudia Mihalcea, Claudio Smiraglia, Elisa Vuillermoz, Daniele Bocchiola |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042003
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| Zusammenfassung |
| Since 26th September 2005 an Automatic Weather Station (AWS1 Forni) has been running
on the ablation area of the largest Italian valley glacier, Forni, (ca. 12 km2 of surface area in
the Ortles-Cevedale group, Stelvio National Park, Lombardy Alps). The WGS84
coordinates of the AWS1 Forni are given by: 46Ë 23’ 56.0” N (46.399Ë N), 10Ë 35’
25.2” E (10.590Ë E), ca. 2700 m, on the lower glacier sector, about 800 m far from
the glacier front. From 2009 the AWS was inserted in the CEOP network in the
frame of the GEWEX project. The AWS is managed by UNIMI and EvK2CNR
Committee.
A four year record (from 1stOctober 2005 to 30th September 2009) of meteorological
data is analyzed: air temperature, relative humidity, wind speed and direction, incoming and
outgoing energy fluxes, air pressure, liquid precipitation and snow depth. This permitted to
characterize the glacier surface conditions, the calculation of the energy balance and the
evaluation of the ablation amount; moreover snow accumulation was considered thus
permitting to estimate the glacier mass balance.
The mean value of 150.72 W m-2 of measured global radiation is obtained. A
comparison with the annual mean extraterrestrial irradiance, 266.82 W m-2, evidences the
topography influence (N aspect) and cloud-effect which strongly decrease the amount
of solar energy impinging on the glacier surface (with a reduction of ca. 44%).
Albedo showed a strong inter annual variability with a mean annual value of 0.65; the
lowest value of 0.63 was registered in 2006 and 2007 correlated to the fresh snow
amount.
Considering only hours characterized by melting and condensation (i.e. melting occurs
about 46.8% of the time and condensation 1.9% of the time), the parameter most influencing
the surface energy balance is the net shortwave radiation (with an average during melting of
128.3 W m-2 and during condensation of 438 W m-2). During melting the net energy
resulted up to five-fold higher than during condensation and during melting the net
longwave radiation revealed stronger negative values (-37.9 W m-2, instead during
condensation -23.4 W m-2). Latent heat flux was characterized by opposite values:
negative during melting (-1.09 W m-2) and positive during condensation (23.3 W
m-2).
The cumulative ablation curve over the entire period was calculated through the complete
energy balance considering only hours characterized by melting. The total melt value resulted
-22.7 kg/m2 or m w.e. Furthermore, for a period of ca. 30 days in summer 2009, an
ablation stake was installed nearby AWS1 Forni to compare measured mass loss with
calculated one; the comparison supports calculation of melting from measured energy
fluxes.
Snowfall measurement represents a key element for evaluating glacier accumulation. The
total value of solid precipitations (obtained from sonic ranger hourly measurements) resulted
+7.21 m w.e., in particularly the yearly precipitation amount results quite constant over the
four analyzed years with only one exception for year 2008 which was characterized by
stronger snowfall (i.e.: 2.03 m w.e.).
Analyzing the calculated mass balance at a daily scale it results mass losses prevailing to
gains: the latter do not exceed +0.05 m w.e. /day, instead losses are up to -0.08 m
w.e./day.
The calculated melting was added to snow accumulation thus giving the specific annual
mass balance (B) at the location of the AWS1 Forni. B resulted equal to ca. -15.5 m
w.e.
Moreover our data permitted further analysis to detect the factors mainly driving the
glacier mass balance. |
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