Abstract
Monitoring of snow and ice is of importance for meteorological and climate research and applications, for hydrological purposes and for navigation and offshore activity in polar regions. For some of these applications long-term monitoring on a mesoscale and a synoptic scale is sufficient, whereas other applications require short-term observation on a mesoscale. This applies especially to forecasting of sea ice conditions, for instance. In the latter cases microwave remote sensing is the only technique that may deliver reliable and timely data irrespective of light, weather and cloud conditions. In the polar regions, this feature is of utmost importance. All known microwave remote-sensing techniques have demonstrated their applicability in polar regions, in particular in connection with observations of sea ice. It has also been shown that a combination of simultaneously acquired data from different sensors may be of advantage in parameter retrieval. This paper reviews the monitoring requirements and the microwave techniques available for this purpose with a view to snow and sea ice research and applications.