Comparison of methods for melt detection over Greenland using active and passive microwave measurements

Microwave measurements have been used in various studies to detect melt based on their sensitivity to liquid water present in snow. To contrast different melt detection methods used with different sensors, six different melt detection method/sensor combinations are compared using data for the summer of 2000. The sensors include the Special Spectral Microwave Imager (SSM/I), SeaWinds on QuikSCAT (QSCAT), and the European Remote Sensing (ERS) Advanced Microwave Instrument (AMI) in scatterometer mode. Existing melt detection methods are compared with melt detection based on a simple physical model. The model relates the moisture content and depth of a surface melt layer of wet snow to a single channel melt detection threshold. The model can be applied to both active and passive sensors and improves the consistency between brightness temperature (Tb) and normalized radar backscatter (su) based detection of melt. Model-based melt estimates from different sensors are highly correlated and do not exhibit the unnatural phenomenon observed with previous methods. Relative merits and limitations of the various methods are discussed.