Mapping and modelling the snowmelt and greening pattern in southern norway by combining microwave and optical remote sensing sensors

Southern Norway has strong climatic gradients and is well suited for studying snow melt and greening patterns. In this study we combine snow cover maps with phenological maps for the early May period for the years 2004 and 2006. The snow cover area maps are based on both microwave (ASAR) and optical (MODIS) sensors. The phenological maps are based on NDVI thresholds from the MODIS sensor. The onset of growing season 2004 was among the earliest recorded over the last 30 years. On May 8, 2004 30% of the study area was covered by snow and 29% had unfolded leaves on trees. The onset of the growing season in 2006 was slightly later than average, and on May 4, 2006 64% of southern Norway was covered by snow and the phenophase of unfolded leaves had not started yet.