Comparison of SSM/I SWE with Modelled Snowpack for Mattagami Watershed

Microwave-frequency data acquired from the Special Sensor Microwave Imager (SSM/I) has been interpreted as snow-water equivalent (SWE) for the snowpack on the upper Mattagami river watershed for the winter of 1998–1999. The Mattagami watershed is in a forested region of Ontario, Canada. Less than 10% of the area is lake or unforested wetland. The algorithm applied to the SSM/I data uses the difference in brightness temperatures registered on the 19 and 37 GHz frequencies as an indicator of the solid (ice-crystal) content of the snowpack. The algorithm was developed for dry snowpack and is invalid for snow with liquid water present. The snowpack water equivalence has been modelled using daily precipitation and air temperature data collected at three different weather stations and an ASAAM algorithm. The snowpack SWE derived from the SSM/I data shows an accumulation and ablation pattern similar to that obtained from the model results and from the limited snowcourse data available. The SSM/I readings appear to be interpreted best under cold conditions (<–10oC) while factors such as snowfall and cloud cover do not appear to have a great effect on the accuracy of the SSM/I interpretation.