SNOW PARAMETERS DERIVED FROM MICROWAVE MEASUREMENTS DURING THE BOREASWINTER FIELD CAMPAIGN

Passive microwave data have been used to infer the snow-covered area a nd snow water equivalent (SWE) over forested areas, but the accuracy o f these retrieved snow parameters cannot be easily validated for heter ogeneous vegetated regions. The Boreal Ecosystem-Atmosphere Study Wint er Field Campaign provided the opportunity to study the effect of bore al forests on snow parameter retrieval in detail. Microwave radiometer s (18, 37, and 92 GHz) were flown on board the Canadian National Aeron autical Establishment's Twin Otter. Flight lines covered both the sout hern study area near Prince Albert and the northern study area near Th ompson, Canada. During the 1994 winter campaign, extensive ground-base d snow cover information, including depth, density, and grain size, wa s collected along most of the flight lines, jointly by U.S. and Canadi an investigators. Satellite data collected by the special sensor micro wave imager are also used for comparison. Preliminary results reconfir med the relationship between microwave brightness temperature and SWE. However, the effect of forest cover observed by the aircraft sensors is different from that of the satellite observations. This is probably due to the difference in footprint averaging. There were also several flight lines flown over Candle Lake and Waskesiu Lake to assess lake ice signatures. Preliminary results show the thickness of the lake ice may be inferred from the airborne microwave observations. The microwa ve signature relationship between lake ice and snow matches the result s from radiative transfer calculations.