Development of SAR-Based Snow-Covered Area Estimation Method for Borel Forest Zone

Development of an enhanced method for fractional snow-covered area (SCA) estimation for the boreal forest zone is presented. The TKK snow-covered area estimation method was developed and demonstrated for northern boreal forest zone using ERS, Envisat ASAR and Radarsat C-band synthetic aperture radar (SAR) data. The new enhanced approach for SCA estimation, presented here, merges the proven TKK SCA estimation method with several new innovations, enhancing its reliability and accuracy in operational use. The enhancements that form the new method include the weather station assimilation method presented earlier and a new reference data selection process. The SCA estimates acquired with the enhanced method are compared with optical satellite data-based (MODIS) SCA data. The results show a significant increase in accuracy when the enhanced SCA method is applied. Correlation between the radar-based and optical comparison data increases from 0.914 to 0.947 and RMS-error improves from 0.151 to 0.123 when the new method is employed. Additionally the SCA estimation method is adapted to produce SCA estimates in 5 km times 5 km spatial resolution. The analyses for the 5 km times 5 km method indicate poorer estimation accuracy than the nominal drainage-basin-based method.