Snow Monitoring Using Radar and Optical Satellite Data

In 1997 HUT, FEI, and FGI started a joint project that aims to develop an operational snow monitoring system in Finland. This project should apply both traditional methods (in situ measurements and hydrological models) and satellite-borne data (ERS-2 SAR and NOAA AVHRR). The emphasis of the project is to develop methods to monitor the snow melt period during spring time. The test site is located in northern Finland, and it consists of the drainage area of River Kemi, which is the largest river in Finland. A total of 18 ERS-2 SAR and six cloudless AVHRR images have been acquired from the test site during the spring of 1997. These images cover totally the snow melt period starting from dry snow and ending to snow-free ground. The optical and microwave radar data sets were compared to each other and to in situ measurements made on the weather stations which are used for current operative snow mapping. The results show that SAR-derived snow cover maps agree reasonably well with ground based observations, and they have a good correlation with AVHRR reflectance for open areas (r=0.82), and even in the presence of vegetation the correlation is relatively high (r=0.77).