Cold-to-warm flow regime transition in snow avalanches

Large avalanches usually encounter different snow conditions along their track. When they release as slab avalanches comprising cold snow, they can subsequently develop into powder snow avalanches entraining snow as they move down the mountain. Typically, this entrained snow will be cold (T‾&lt;-1&thinsp;∘C) at high elevations near the surface, but warm (T‾&gt;-1&thinsp;∘C) at lower elevations or deeper in the snowpack. The intake of warm snow is believed to be of major importance to increase the temperature of the snow composition in the avalanche and eventually cause a flow regime transition. Measurements of flow regime transitions are performed at the Vallée de la Sionne avalanche test site in Switzerland using two different radar systems. The data are then combined with snow temperatures calculated with the snow cover model SNOWPACK. We define transitions as complete when the deposit at runout is characterized only by warm snow or as partial if there is a warm flow regime, but the farthest deposit is characterized by cold snow. We introduce a transition index Ft, based on the runout of cold and warm flow regimes, as a measure to quantify the transition type. Finally, we parameterize the snow cover temperature along the avalanche track by the altitude Hs, which represents the point where the average temperature of the uppermost 0.5&thinsp;m changes from cold to warm. We find that Ft is related to the snow cover properties, i.e. approximately proportional to Hs. Thus, the flow regime in the runout area and the type of transition can be predicted by knowing the snow cover temperature distribution. We find that, if Hs is more than 500&thinsp;m above the valley floor for the path geometry of Vallée de la Sionne, entrainment of warm surface snow leads to a complete flow regime transition and the runout area is reached by only warm flow regimes. Such knowledge is of great importance since the impact pressure and the effectiveness of protection measures are greatly dependent on the flow regime.</p

Climate Scenarios for Switzerland CH2018 – Approach and Implications

To make sound decisions in the face of climate change, government agencies, policymakers and private stakeholders require suitable climate information on local to regional scales. In Switzerland, the development of climate change scenarios is strongly linked to the climate adaptation strategy of the Confederation. The current climate scenarios for Switzerland CH2018 - released in form of six user-oriented products - were the result of an intensive collaboration between academia and administration under the umbrella of the National Centre for Climate Services (NCCS), accounting for user needs and stakeholder dialogues from the beginning. A rigorous scientific concept ensured consistency throughout the various analysis steps of the EURO-CORDEX projections and a common procedure on how to extract robust results and deal with associated uncertainties. The main results show that Switzerland’s climate will face dry summers, heavy precipitation, more hot days and snow-scarce winters. Approximately half of these changes could be alleviated by mid-century through strong global mitigation efforts. A comprehensive communication concept ensured that the results were rolled out and distilled in specific user-oriented communication measures to increase their uptake and to make them actionable. A narrative approach with four fictitious persons was used to communicate the key messages to the general public. Three years after the release, the climate scenarios have proven to be an indispensable information basis for users in climate adaptation and for downstream applications. Potential for extensions and updates has been identified since then and will shape the concept and planning of the next scenario generation in Switzerland

Reptile remains from Tiga (Tokanod), Loyalty Islands, New Caledonia

Archaeological excavations on Tiga provide the first vouchered herpetological records for this small island between Lifou and Maré in the Loyalty Islands. Eighty-three skeletal elements from four sites yielded material assignable to skinks (Emoia loyaltiensis, Lioscincus nigrofasciolatus), geckos (Bavayia crass i-collis, B. sp., Gehyra georgpotthasti, Nactus pelagicus), and a boid snake (Candoia bihroni) all known from elsewhere in the Loyalties, as well as undetermined material consistent with these and other Loyalties lizards. Diagnostic features of geckos versus skinks for elements commonly recovered from archaeological sites and from owl pellets are discussed. Gehyra georgpotthasti has a limited distribution in the Loyalties and its occurrence on Tiga clarifies its range. The boid snake is the only reptile likely to have been harvested by human inhabitants of Tiga. The presence of gekkonid geckos in pre-European times is confirmed and contrasts with the situation of Grande Terre fossil sites, where only diplodactylid geckos have been recovered. Although it is anticipated that all species recovered from archaeological sites are still present on the island, a modern herpetofaunal survey is needed

Les aciers électriques pour transformateurs et machines tournantes. Situation actuelle et perspectives

Pas de Résumé disponibl