Snow measurement techniques for land-surface-atmosphere exchange studies in boreal landscapes

Snow has been studied widely in hydrology for many decades whereas recent m eteorological interest in snow is caused by increased emphasis on high lati tudes and wintertime in climate-change research as well as by the need to i mprove weather-forecast models during these conditions. Ground-based measur ements of snow properties are needed both to improve understanding of surfa ce-atmosphere exchange processes and to provide ground truth to new remote- sensing algorithms. This justifies a review of techniques to measure snow i n combination with establishment of criteria for the suitability of the met hods for process studies. This review assesses the state-of-art in ground-b ased snow-measurement techniques in the end of the 1990s in view of their a ccuracy, time resolution, possibility to automate, practicality and suitabi lity in different terrain. Methods for snow-pack water equivalent, depth, d ensity, growth, quality, liquid-water content and water leaving the snow pa ck are reviewed. Synoptic snow measurements in Fennoscandian countries are widely varying and there is no single standard on which process-related stu dies can build. A long-term, continuous monitoring of mass and energy prope rties of a snow cover requires a combination of point-measurement technique s. Areally representative values of snow properties can be achieved through a combination of automatically collected point data with repeated manual, areally covering measurements, remote-sensing data and digital elevation mo dels, preferably in a GIS framework.