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Zürich, Switzerland

Gurgiser W.,University of Innsbruck | Juen I.,University of Innsbruck | Singer K.,University of Hamburg | Neuburger M.,University of Hamburg | And 4 more authors.
Earth System Dynamics | Year: 2016

Pronounced hygric seasonality determines the regional climate and, thus, the characteristics of rainfed agriculture in the Peruvian Callejón de Huaylas (Cordillera Blanca). Peasants in the Cuenca Auqui on the eastern slopes above the city of Huaraz attribute recently experienced challenges in agricultural production mainly to perceived changes in precipitation patterns. Statistical analyses of daily precipitation records at nearby Recuay (1964 to 2013) and Huaraz (1996 to 2013) stations do not corroborate the perceived changes. Either insufficient temporal resolution of available precipitation records or other environmental and sociopolitical factors impacting traditional farming methods may be the reason for the lack of concordance between the two information sources investigated in this study. © 2016 Author(s). Source


Golle I.,SBB AG | Holderegger M.,SBB AG | Steinegger U.,Meteodat GmbH
eb - Elektrische Bahnen | Year: 2015

The heating of the components of overhead contact lines depends not only on the flowing currents but also on the ambient meteorological conditions. Solar heating, velocity and direction of the wind and air temperature form essential effects. Swiss Railways SBB developed models for calculating the thermal behavior of contact lines which adequately consider these factors. The models were validated by measurements at overhead contact lines in operation. It is planned to utilize the results for parameterizing the thermal contact line protection equipment. Source


Salzmann N.,University of Zurich | Salzmann N.,University of Fribourg | Huggel C.,University of Zurich | Rohrer M.,Meteodat GmbH | And 4 more authors.
Cryosphere | Year: 2013

The role of glaciers as temporal water reservoirs is particularly pronounced in the (outer) tropics because of the very distinct wet/dry seasons. Rapid glacier retreat caused by climatic changes is thus a major concern, and decision makers demand urgently for regional/local glacier evolution trends, ice mass estimates and runoff assessments. However, in remote mountain areas, spatial and temporal data coverage is typically very scarce and this is further complicated by a high spatial and temporal variability in regions with complex topography. Here, we present an approach on how to deal with these constraints. For the Cordillera Vilcanota (southern Peruvian Andes), which is the second largest glacierized cordillera in Peru (after the Cordillera Blanca) and also comprises the Quelccaya Ice Cap, we assimilate a comprehensive multi-decadal collection of available glacier and climate data from multiple sources (satellite images, meteorological station data and climate reanalysis), and analyze them for respective changes in glacier area and volume and related trends in air temperature, precipitation and in a more general manner for specific humidity. While we found only marginal glacier changes between 1962 and 1985, there has been a massive ice loss since 1985 (about 30% of area and about 45% of volume). These high numbers corroborate studies from other glacierized cordilleras in Peru. The climate data show overall a moderate increase in air temperature, mostly weak and not significant trends for precipitation sums and probably cannot in full explain the observed substantial ice loss. Therefore, the likely increase of specific humidity in the upper troposphere, where the glaciers are located, is further discussed and we conclude that it played a major role in the observed massive ice loss of the Cordillera Vilcanota over the past decades. © Author(s) 2013. Source


Sorg A.,University of Geneva | Sorg A.,University of Bern | Huss M.,University of Fribourg | Rohrer M.,Meteodat GmbH | And 2 more authors.
Environmental Research Letters | Year: 2014

Despite the fact that the fast-growing population of Central Asia strongly depends on glacial melt water for fresh water supply, irrigation and hydropower production, the impact of glacier shrinkage on water availability remains poorly understood. With an annual area loss of 0.36 to 0.76%, glaciers are retreating particularly fast in the northern Tien Shan, thus causing concern about future water security in the densely populated regions of Bishkek and Almaty. Here, we use exceptionally long in-situ data series to run and calibrate a distributed glacio-hydrological model, which we then force with downscaled data from phase five of the Climate Model Intercomparison Project CMIP5. We observe that even in the most glacier-friendly scenario, glaciers will lose up to two thirds (-60%) of their 1955 extent by the end of the 21st century. The range of climate scenarios translates into different changes in overall water availability, from peak water being reached in the 2020s over a gradual decrease to status quo until the end of the 21st century. The days of plenty, however, will not last much longer, as summer runoff is projected to decrease, independent of scenario uncertainty. These results highlight the need for immediate planning of mitigation measures in the agricultural and energy sectors to assure long-term water security in the densely populated forelands of the Tien Shan. © 2014 IOP Publishing Ltd. Source


Salzmann N.,University of Fribourg | Salzmann N.,University of Zurich | Huggel C.,University of Zurich | Rohrer M.,Meteodat GmbH | And 2 more authors.
Journal of Hydrology | Year: 2014

Glacier and snow cover changes with related impacts on melt runoff can seriously affect human societies which are depending on fresh water from cryospheric sources. Observed trends and projected future evolutions of climatic and cryospheric variables clearly show the need to adapt to these changes. Accordingly, the topics addressed herein have been put on the agendas of many larger funding agencies. This article provides a brief overview on major ongoing activities on glacier, snow and related runoff research in order to then analyze data gaps and research needs from a climate change adaptation perspective. Major data needs are identified with respect to the spatial and temporal coverage of local-scale data and related needs for (data) services that distribute and maintain these data sets. Moreover, clear research needs are also recognized at the local scale where process knowledge needs to be improved (e.g., the influence of albedo on snow and ice or debris cover on glaciers) in order to derive plausible climate change impacts assessments. The paper then discusses directions on how to move forward to better serve the practical needs for climate change adaptation planning. In the future, substantial support by large funding agencies might be key for capacity building in target regions of climate change adaptation programs, for longer-term and more sustainable commitments, and for the development of approaches, which aim at assessing the transferability of data, techniques, and tools. © 2014 Elsevier B.V. Source

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