Estimation of areal snow water equivalent from space-borne microwave observations

The feasibility of space-borne microwave radiometers for monitoring the evolution of snow-cover in a drainage area is investigated. A four-winter set of SSM/I radiometer observations for the 51,000 km² River Kemijoki drainage area, Northern Finland, are used for analyses. The results indicate that the used microwave emission model-based automatic inversion algorithm can estimate the regional Snow Water Equivalent (SWE) under dry snow conditions with an overall RMSE of ~30 mm without using any training reference data on SWE. The retrieval error was found to vary considerably from year to year. At the best, the annual SWE retrieval RMSE showed values as low as ~20 mm