Christian Jaedicke

SNOW MASS QUANTIFICATION AND AVALANCHE VICTIM SEARCH BY GROUND PENETRATING RADAR

Ground penetrating radar (GPR) systems can be used in many applications of snow and ice research. The information from the GPR is used to identify and interpret layers, objects and different structures in the snow. A commercially available GPR system was further developed to work in the rough environment of snow and ice. The applied GPR is a 900 MHz system that easily reaches snow depths of up to 10 meters. The system was calibrated in the course of several manual snow depth measurements during each survey. The depth resolution depends on the snow type and is around ±0.1 m. The GPR system is carried alongside a line of interest and is triggered by an odometer wheel at regular adjustable steps. All equipment is mounted in a sledge and is pulled by a snowmobile over the snow surface. This setup allows for an efficient coverage of several kilometers of terrain profiles. The radar profiles give a real time two-dimensional impression of structures and objects and the interface between snow and the underlying ground. The actual radar profile is shown on a screen on the sledge allowing the immediate marking of objects and structures. During the past three years the instrument was successfully used for the study of snow distributions, for the detection of glacier crevasses under the snow cover, and for the search of avalanche victims in avalanche debris. The results show the capability of the instrument to detect persons and objects in the snow cover. In the future, this device may be a new tool for avalanche rescue operations. Today, the size and weight of the system prevents the accessing of very steep slopes and areas not accessible to snowmobiles. Further developments will decrease the size of the system and make it a valuable tool to quantify snow masses in avalanche release zones and run-out areas.

Acoustic snowdrift measurements: experiences from the FlowCapt instrument

Abstract Three acoustic FlowCapt™ (IAV Engineering) drifting snow instruments were deployed during the 1999 and 2000 field season on Spitsbergen, Norway. Three different experiments were carried out to test the instruments for their use in snowdrift research. The data from the three instruments were compared during a study of drifting snow within an Arctic catchment and around a building. The principle of the instruments is based on the acoustic signal, generated by the mechanical impact of drifting snow particles on a vertical tube. Microphones inside the tube transmit the signal to a frequency analyser. By Fourier transformation, the signal can be divided into the high frequencies of the impacting snow particles and the low frequencies, resulting from the loosening wake eddies behind the tube. In this way, both snow drift flux and wind speed can be measured simultaneously. Results from the three experiments show that the instruments are useful tools to study drifting snow in remote areas. A reliable indication of the occurrence and strength of drifting snow events can be determined even if the absolute accuracy is difficult to quantify.

Snow drift losses from an Arctic catchment on Spitsbergen: an additional process in the water balance

Blowing snow is a process, which can be observed during the entire winter season in Arctic catchments. On Spitsbergen at 78° North, the ground is bare of tall vegetation and the snow is easily moved by the wind. During frequent storms, large masses of snow are relocated from erosion to deposition areas. In this study, the mass of snow, transported out of an Arctic valley to the open sea is estimated via direct measurements and model calculations. The study area is a valley on Spitsbergen in the high Arctic. The valley is approximately 4 km wide and 10 km long and ends in a fjord arm. The wind direction in the valley is very uniform. During the winter season, the wind is blowing out of the valley 80% of the time. There is one permanent automatic weather station located in the valley. In addition, three automatic weather stations were installed in the valley during a study period of 2 months in February and March 2000. These stations measure, in addition to wind speed and direction, the snow drift flux with acoustic snow drift sensors. The results of the study period are related to those of the permanent station to quantify the accumulated snow mass passing from the valley to the open sea for the entire season. The results show that the transport snow mass equals 0.2% of the annual precipitation in the catchment. Thus, the losses due to snow drift to the open sea are of little importance to the valleys water balance.

GIS-aided avalanche warning in Norway

Avalanche warning for large areas requires the processing of an extensive amount of data. Information relating to the three basic requirements for avalanche warning - knowledge of terrain, the snow conditions, and the weather - needs to be available for the forecaster. The information is highly variable in time. The form and visualization of the data is often decisive for the use by the avalanche forecasters and therefore also for the quality of the produced forecasts. Avalanche warnings can be issued at different scales from national to regional and down to object specific. Often the same warning service is working at different scales and for different clients requiring a flexible and scalable approach. The workflow for producing avalanche forecasts must be extremely efficient - all the way from acquiring observation data, evaluating the situation, down to publishing the new forecast. In this study it has been an aim to include the entire workflow in a single web application. A Geographic Information Systems (GIS) solution was chosen to include all data needed by the forecaster for the avalanche danger evaluation. This interactive system of maps features background information for the entire country, such as topographic maps, slope steepness, aspect, hill shades and satellite images. In each avalanche warning area, all active avalanche paths are plotted including information on wind exposure. Each avalanche path is linked to a webpage with more details, such as fall height, release area elevation and pictures. The avalanche path webpage also includes information on the object at risk e.g. buildings, roads, or other objects. Thus, the forecaster can easily get an overview on the overall situation and focus on single avalanche paths to generate detailed avalanche warnings for the client. A GIS-based web application for local avalanche warning in Norway is presented that provides a useful platform to gather and present the data for the avalanche forecaster.Local and regional avalanche warnings need to consider spatial data from many different sources that changes from hour to hour.The all in one tool allows the avalanche forecaster to follow a standardized workflowfrom data acquisition to publishing the final avalanche warning product.Improved structure, easy access and user-friendliness in the map based system are superior to paper reports, different websitesand stand alone applications.Online solutions allow for an easy access to the tools from various platforms, such as PC, smart phone or tablet.