Retrieval of snow information using passive microwave data in Norway

In several regions of the world, a major part of the annual precipitation is stored in the snowpack during winter. In Norway, more than half of the land area is located above the tree line. It is important to monitor the behaviour of the snowpack in this region throughout the winter, as it contributes considerable to run-off during spring and summer. Measurements on the snow water equivalent (SWE) are limited in space and time, however as such observations are associated with high costs and limited in situ networks. Remote sensing of microwave radiation emitted by the snow covered ground makes it possible to retrieve spatially- and temporally- distributed SWE proxy data, as the ground-based radiation is modified by snowpack. In this study, an evaluation of Special Sensor Microwave / Imager (SSM/I) derived SWE is carried out for two large high-mountain plataus in northern and southern Norway. Snow information is derived from SSM/I brightness temperatures and compared with in situ measurements and simulations of snow characteristics. A degree-day based snow model is developed and used for comparison with the SSM/I-derived SWE estimates. The model calculates snow properties, such as SWE, liquid water content, and state of precipitation. Output from the model and in situ observations are used to derive information on other snow properties such as snow metamorphosis. This study yilds obvious correlation between SSM/I derived SWE and model simulated SWE based on precipitaion and temperature, although a one-to-one relation is more difficult to establish.