The Multiple Waveform Persistent Peak (MWaPP) Retracker for SAR waveforms

Here we present a new method for retracking of SAR waveforms over rivers and lakes. Satellite altimetry offers frequent and global sampling across borders, which can be used to validate and calibrate hydrological models in remote areas where in situ measurements are scarce. The method was developed using CryoSat-2 20Hz SAR data, but due to the similarities between the Sentinel-3 SRAL altimeter and the SIRAL altimeter on-board CryoSat-2 an adaption of the method will be straightforward.

The MWaPP retracker is based on a sub-waveform retracker, but takes the shape of adjacent waveforms into account before selecting the sub-waveform belonging to nadir. This is new compared to primary peak retrackers, and alleviates a lot of snagging due to off-nadir bright targets, but also topography challenges.

The results from the MWaPP retracker show a significant decrease in the standard deviation of the mean of various lake and river crossings throughout the world. Results are presented for rivers and lakes, such as The Brahmaputra River, The Amazon River, The River Thames, and for Lake Vänern in Sweden and Lake Okeechobee in Florida, US.