Evaluating spaceborne passive microwave snow water equivalent retrievals across the Canadian northern boreal - tundra ecotone

Time series analysis of the spaceborne passive microwave data record (1978-present) has identified an interannually consistent zone of high snow water equivalent (SWE) retrievals across the northern boreal forest of Western Canada. Because of potentially significant hydrological and climatological implications, and the sparse conventional observing network across this region, a dedicated field sampling campaign was conducted to verify the existence of this pattern. Snow measurements were made along an approximately 500 km transect across Northern Manitoba, Canada, during late November 2003 and early March 2004. Both snow surveys revealed strong agreement between Special Sensor Microwave/Imager (SSM/I) derived passive microwave SWE retrievals (using the Meteorological Service of Canada algorithm suite) and in situ measurements across the northern boreal forest: a gradient of increasing SWE between Thompson and Gillam was evident, as was a well defined zone of high SWE values to the north and east of Gillam. Further to the north, SSM/I derived SWE retrievals over the open tundra were anomalously low. These findings suggest that development of a tundra-specific SWE retrieval algorithm is necessary, given the unique snow pack properties, and high fraction of surface water (frozen lakes)