Validation of cryoSat-2 based lake levels

In this study, which is part of the FP7 project Land and Ocean take up from Sentinel-3 (LOTUS), we demonstrate the potential SAR altimetry. We consider lakes at various sizes and evaluate the CryoSat-2 derived lake levels in terms of along-track precision and agreement with in-situ data. As a reference we compare our CryoSat based results with conventional altimetry such as Envisat.
We find that the precision of the along-track mean water level is a few cm, evenfor lakes with a surface of just 9 km2. The high precision makes it possible to detect water level variation below the decimeter level.
To derive lake level time series we apply a state-space model with a robust handling of erroneous data. Instead of attempting to identify and remove the polluted observations we use a mixture distribution to describe the observation noise, which prevents the polluted observations from biasing our final reconstructed time series.
These results demonstrate the promising possibilities of the upcoming mission Sentinel-3, which potentially will be able to provide accurate time series for small lakes.