312 research outputs found
Simulazione della fusione in ambiente glaciale con un modello distribuito ad indice morfoenergetico
No full textEISModel is a snow accumulation and melt model that combines the classical temperature index approach with a distributed radiation index, computed accounting for astronomical radiation and local topography. In former applications the model showed a good ability to follow the spatial variability of snow cover during the melt season. It uses few parameters an few meteorological data thus being a potentially interesting tool even in glacial environment, where often data and parameters required for a physically based approach are not fully available. Anyway melt modelling over a glacial surface must take into account even factors that normally, in case of snow melt over ground, can be neglected, as the albedo seasonal variation or the surface topography changes in longer periods. The model was employed to simulate two ablation seasons in the alpine Agola glacier (Brenta Dolomites), comparing the results with detailed field surveys dat
Enhanced estimation of glacier mass balance in unsampled areas by means of topographic data
No full textA new method was developed to estimate the mass balance in unsampled areas from existing
datasets. Three years of mass-balance data from two glaciers in the central Italian Alps were used to
develop and test a multiple-regression method based exclusively on a 10 m resolution digital terrain
model. The introduction of a relative elevation attribute, which expresses the degree of wind exposure of
the gridcells, notably increased the amount of explainable variance in winter balance with respect to
altitude itself. The summer balance is highly correlated with elevation, but, in order to obtain reliable
extrapolations, the clear-sky shortwave radiation and the diurnal cloud-cover cycle had to be taken into
account. The net annual mass balance on a glacier system comprising the two monitored glaciers was
calculated by applying both a single regression of winter and summer balance with altitude and the new
regression method. The consistency of results was assessed against measured net balances and snow-cover maps drawn in the ablation season. The results of the new method were in close agreement with
observations and proved to be less sensitive to the spatial representation of the sampled area
Variabilità spaziale dell'albedo sulle aree glaciali dell'Alta Val de La Mare (Gruppo Ortles-Cevedale)
No full textNell’ambito di un progetto di ricerca sulla criosfera e sugli effetti idrologici delle variazioni climatiche nei bacini di alta quota, è stato eseguito uno studio sulla va- riabilità spaziale dell’albedo in ghiacciaio. La campagna di rilievi è stata condotta nelle estati del 2007 e del 2008 sui ghiacciai dell’alta Val de La Mare (Gruppo Ortles-Cevedale, Trentino).
L’albedo regola la quantità di radiazione ad onde corte assorbita dalla superficie ed è quindi determinante nel modulare il bilancio energetico e il bilancio di massa glaciale. Le parametrizzazioni comunemente riportate nella letteratura scientifica sono generalmente orientate alla descrizione della variabilità spazio-temporale dell’albedo della neve, mentre l’albedo del ghiaccio è spesso assunto costante o parametrizzato in modo molto più semplice, ad esempio in funzione della quota. I rilievi eseguiti in alta Val de La Mare evidenziano un’elevata variabilità dell’albe- do del ghiaccio di ghiacciaio, che è funzione soprattutto della copertura detritica superficiale. Sulla base di queste osservazioni, si è cercato di mettere a punto un metodo speditivo che consente una valutazione semplice ed affidabile dell’albedo, basato su rilievi fotografici da terra. I risultati ottenuti confermano che il metodo proposto consente di cogliere in modo adeguato la variabilità spaziale dell’albedo sul ghiaccio di ghiacciaio
Distributed mass balance modelling on two nearby glaciers of Ortles-Cevedale (Italy) from 2004 to 2009
No full textA 6 year application of an enhanced temperature-index mass-balance model to Careser and
La Mare glaciers, Eastern Italian Alps, is presented. The two glaciers exhibit very different
characteristics, and a comprehensive dataset of distributed mass-balance measurements was used to
test the model performance. The model was run using meteorological data acquired outside the glaciers.
The work was focused on two main aspects: (1) the development of a morphological redistribution
procedure for snow, and (2) the comparison of three different melt algorithms proposed in the literature.
The results show that the simple method proposed for snow redistribution can greatly improve
simulation of winter balance, and further improvements would be achievable by collecting data on
inaccessible and high-altitude areas. All three melt formulations displayed a good skill level and very
similar results in modelling the mass-balance distribution over glacier areas, with slightly better results
from a multiplicative algorithm in capturing the vertical balance gradient. The simulation errors are
related to aspect and elevation, and tend to be spatially aggregated. Some assumptions concerning the
spatial and temporal distribution of air temperature and incoming solar radiation, although reasonable
and widely used in the literature, may be responsible for this aggregation. Hence, there is a need to
further investigate the processes that regulate the distribution of melt energy, and that appear to control
the current deglaciation phase in this area
On the disequilibrium response and climate change vulnerability of the mass-balance glaciers in the Alps
No full textGlaciers in the Alps and several other regions in the world have experienced strong negative mass balances over the past few decades. Some of them are disappearing, undergoing exceptionally negative mass balances that impact the mean regional value, and require replacement. In this study, we analyse the geomorphometric characteristics of 46 mass-balance glaciers in the Alps and the long-term mass-balance time series for a subset of nine reference glaciers. We identify regime shifts in the mass-balance time series (when non-climatic controls started impacting) and develop a glacier vulnerability index (GVI) as a proxy for their possible future development, based on criteria such as hypsometric index, breaks in slope, thickness distribution and elevation change pattern. We found that the subset of 46 mass-balance glaciers reflects the characteristics of the total glacier sample very well and identified a region-specific variability of the mass balance. As the GVI is strongly related to cumulative glacier mass balances, it can be used as a pre-selector of future mass-balance glaciers. We conclude that measurements on rapidly shrinking glaciers should be continued as long as possible to identify regime shifts in hind-cast and better understand the impacts of climatic variability on such glaciers
Effects of business recovery strategies on seismic risk and cost-effectiveness of structural retrofitting for business enterprises
No full textRecent earthquakes in Italy have significantly affected productive activities, particularly in business interruption (BI) and, consequently, heavy losses for companies, highlighting the need for appropriate seismic risk assessment and management. To estimate seismic risk accurately, both direct (repair/ replacement) and indirect (BI) losses must be quantified. Companies’ balance sheets can be used to estimate BI losses, which, however, are very sensitive to business recovery strategies (BRSs) devised by corporate managers after the seismic event. The aim of this study is to evaluate the effects of BRSs on seismic risk estimates and consequently on structural retrofitting cost-effectiveness. A loss model (including direct and indirect costs and BRS effects) was defined, based on a real-life case study (a biomedical packaging company that was damaged by the 2012 Italian earthquake but recovered soon after) and was used in parametric risk analyses assessing several types of company vulnerabilities and seismic hazards. In areas with low-to-moderate seismicity, seismic retrofitting of existing reinforced concrete factories may be justified or otherwise, depending on whether BRSs are considered or not
Air temperature variability over three glaciers in the Ortles-Cevedale (Italian Alps): Effects of glacier fragmentation, comparison of calculation methods, and impacts on mass balance modeling
No full textGlacier mass balance models rely on accurate spatial calculation of input data, in particular air temperature. Lower temperatures (the so-called glacier cooling effect), and lower temperature variability (the so-called glacier damping effect) generally occur over glaciers, compared to ambient conditions. These effects, which depend on the geometric characteristics of glaciers and display a high spatial and temporal variability, have been mostly investigated on medium- to large-size glaciers so far, while observations on smaller ice bodies are scarce. Using a dataset from 8 on-glacier and 4 off-glacier weather stations, collected in summer 2010 and 2011, we analyzed the air temperature distribution variability and wind regime over three different glaciers in the Ortles-Cevedale. The magnitude of the cooling effect and the occurrence of katabatic boundary layer (KBL) processes showed remarkable differences among the three ice bodies, highlighting suggesting the likely existence of important reinforcing mechanisms during glacier decay and disintegration. None of the methods proposed in the literature for calculating on-glacier temperature from off-glacier data fully reproduced our observations. Among them, the more physically-based procedure of Greuell and Böhm [1998] provided the best overall results where the KBL prevail, but it was not effective elsewhere (i.e. on smaller ice bodies and close to the glacier margins). The accuracy of air temperature estimations strongly impacted the results from a mass balance model which was applied to the three investigated glaciers. Most importantly, even small temperature deviations caused distortions in parameter calibration, thus compromising the model generalizability
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