| Popis: |
For more than 10 years, CryoSat-2 (CS2) has been observing and monitoring the polar regions, providing unprecedented spatial and temporal coverage. Satellite altimetry allows the measurement of sea ice thickness, a key variable for understanding sea ice dynamics. Many products developed by the community have already demonstrated the capabilities of CryoSat-2 to estimate sea ice thickness. Nevertheless, several questions remain to better assess the relevance and quality of the measurements according to the ice type. These include the effects of ice roughness in the footprint and Ku frequency penetration levels in the snow cover. In July 2020, CS2's orbit was raised, as part of the Cryo2Ice project, to have tracks co-located with NASA's high-resolution IceSat-2 altimeter over the Arctic Ocean. These coincident measurements between the Ku-band SAR altimeter for CS2 and the LIDAR altimeter for IceSat-2 provide a unique means of assessing the impact of radar footprints and snow properties in the measurements. Here we present a methodology for comparing IceSat-2 and CryoSat-2 along coincident trajectories and show the potential of using a dual-sensor approach to understand the measurement. Comparisons between surface roughness estimates and snow products show strong correlations, highlighting the cross-effects of penetration and roughness. We then introduce comparisons with SARAL Ka-band data, which does not penetrate snow, to better understand these effects. We also study the impact of CryoSat-2 waveform processing methods, or retrackers, using various sea ice products proposed by the scientific community. This ESA-supported study should help prepare the Copernicus CRISTAL mission, which will include a Ka/Ku dual-frequency altimeter for the first time. |
