Monitoring of seasonal snowmelt on Greenland with ERS scatterometer data

In Greenland, summer melting of snow is common in large areas, and its extent and intensity are expected to respond immediately to climate change. Volume scattering is the dominating backscattering mechanism for snow with volumetric moisture of less than 3%. Free liquid water in the snow causes high dielectric loss, which increases the absorption coefficient. Therefore, the normalized radar cross section of snow decreases with increasing snow wetness when the snow starts melting. The radar cross section measurements over Greenland by the C-band scatterometers aboard the first and second European Remote Sensing Satellite (ERS-1 and ERS-2) were used to detect and monitor snow melt for the period of August 1991 to December 1999. The produced maps of snowmelt show considerable interannual variations in terms of melt extent and intensity. Although climatological trends cannot be delineated from the short time series, the presented technique is well suited for this task. In the future, this type of radar measurement will be continued by the meteorological METOP satellite series. This will offer a unique possibility for climatological studies