The role of Earth Observation in snowmelt runoff monitoring from high latitude basins: SAR aspects

The CEO HYDALP project aims to use Earth Observation data to improve the monitoring and forecasting of snowmelt runoff from alpine and high latitude basins, and to prepare a basis for the operational use of this information. A crucial parameter for snowmelt runoff modelling is the snow covered area. Methods have previously been developed for mapping snow cover in alpine basins using medium and high resolution optical data and for mapping wet snow using synthetic aperture radar (SAR) data. An objective of HYDALP is to determine the applicability of these methods to high latitude basins. This paper discusses the applicability of the SAR wet snow mapping method to high latitude basins and highlights differences with respect to alpine areas. The authors wish to determine: a) If wet snow causes a detectable change in backscatter as compared to no or dry snow cover. b) What the detection and false alarm rates are. c) What other dynamic changes occur within the image and whether these could be mistaken for wet snow. d) How the method is affected by topography and whether ascending and descending pass image combinations are needed to reduce these effects