Monitoring Snow Cover Variations in the Alps Using the Alpine Snow Cover Analysis System (Ascas)

In many instances, snow cover and duration are a major controlling factor on a range of environmental systems in mountain regions. When assessing the impacts of climatic change on mountain ecosystems and river basins whose origin lie in the Alps, one of the key controls on such systems will reside in changes in snow amount and duration. At present, regional climate models or statistical downscaling techniques, which are the principal methods applied to the derivation of climatic variables in a future, changing climate, do not provide adequate information at the scales required for investigations in which snow is playing a major role. A study has thus been undertaken on the behavior of snow in the Swiss Alps, in particular the duration of the seasonal snow-pack, on the basis of observational data from a number of Swiss climatological stations. It is seen that there is a distinct link between snow-cover duration and height (i.e., temperature), and that this link has a specific "signature" according to the type of winter. Milder winters are associated with higher precipitation levels than colder winters, but with more solid precipitation at elevations exceeding 1,700 -2,000 m above sea-level, and more liquid precipitation below. These results can be combined within a single diagram, linking winter minimum temperature, winter precipitation, and snow-cover duration. The resulting contour surfaces can then be used to assess the manner in which the length of the snow-season may change according to specified shifts in temperature and precipitation. While the technique is clearly empirical, it can be combined with regional climate model information to provide a useful estimate of the length of the snow season with snow cover, for various climate-impacts studies.

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Snow pack in the Swiss Alps under changing climatic conditions: an empirical approach for climate impacts studies

Beniston

Keller

Goyette

2003

Theoretical and Applied Climatology

155

114

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Monitoring Swiss alpine snow cover variations using digital NOAA-AVHRR data

Holzer

Baumgartner

Apfl

1995 International Geoscience and Remote Sensing Symposium, IGARSS '95. Quantitative Remote Sensing for Science and Application

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Within a research project and the programm for a Hydrologic Atlas of Switzerland, charts of the extent and the variations of the snow cover in Switzerland for two hydrologically and meteorologically different years were derived from digital NOAA-AVHRR data. During the two years, 32 satellite scenes were classified using supervised classification techniques. For the generation of the snow cover charts, up to 12 categories (several sub-categories for vegetation, water, snow, and clouds) were used. The final results were thematic maps differentiating between snow covered and non-snow covered (aper) areas. The snow cover charts were geocoded to the Swiss reference system using a ground-control-point approach allowing the superimposition onto a Digital Elevation Model @EM) and a digital boundary map of Switzerland within a Geographic Information System (GIS). Based on this data set, the snow coverage and its variations as well as the snowline for the two years under investigation were determined for several river basins in Switzerland. Furthermore, snow cover depletion curves for the two ablation periods, separately for several elevation zones, were generated which were necessary for snowmelt runoff computations in the RhineFelsberg basin using the SRM Model.

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Monitoring Snow Cover Variations in the Alps Using the Alpine Snow Cover Analysis System (Ascas)

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Snow pack in the Swiss Alps under changing climatic conditions: an empirical approach for climate impacts studies

Snow pack in the Swiss Alps under changing climatic conditions: an empirical approach for climate impacts studies

Monitoring Swiss alpine snow cover variations using digital NOAA-AVHRR data

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