Combining Radar Altimetry and Lidar to Study Snow Accumulation

Calibration and validation is essential for the success of a remote sensing satellite missions. In spring 2006 a major CryoSat-2 campaign was carried out in the Arctic to obtain a calibration and validation dataset using lidar, the ASIRAS radar and in-situ measurements. The ASIRAS is an airborne radar which mimics the CryoSat-2 SIRAL instrument. The radar was mounted on an aircraft together with lidar and support instruments throughout the five week long campaign. Studies show that ASIRAS has the capability to detect density variations several meters into the snow pack on ice sheets. When combining the radar measurements with lidar and in-situ measurement it is possible to estimate the yearly snow accumulation on inland ice. Based on the yearly variation in density detected by the radar it is possible to detect several seasons and thus obtain an accumulation history for a specific area. The combination of radar and lidar on a single platform also makes it possible to estimate the snow cover on sea ice. Studies have shown that a good cross calibration between the lidar and the radar can be used to estimate the snow thickness on first year ice, and ongoing studies are examining the possibility to apply the same method on multi year ice. The multi year ice poses difficulties with a high noise level and false reflectors due to the inhomogeneous ice field consisting of old porous ice, refrozen melt water, ridges and new ice.