Retrieving Sea Surface Height from 40-Hz SARAL/AltiKa waveforms for the Gujarat Coast

Rashmi Sharma (ISRO, India)


Aditya Chaudhary (ISRO, India); Seemanth M (ISRO, India); Sujit Basu (ISRO, India); Raj Kumar (ISRO, India)

Event: 2014 SARAL/AltiKa workshop

Session: Instrument processing

Presentation type: Type Poster

Developing a suitable retracking strategy, proper selection of various geophysical and atmospheric corrections for the range measurements and choosing a suitable editing and filtering criteria are key to retrieving Sea Surface Height (SSH) near the coastal and in the shallow water regions. Each coast presents a unique challenge for retrieval of the geophysical parameters because of the complex topography, vegetation and bathymetry. Waveform shapes are quite complex and are very different from the classical Brown shape open ocean waveforms. The availability of high frequency waveform data (40-Hz) from SARAL/AltiKa mission, with better vertical and horizontal resolution opens up an opportunity to derive SSH with higher accuracy. We have used 1-year of data from SARAL/AltiKa S-IGDR data in the Indian coastal region, with emphasis on Gujarat coast. A total of 11 tracks have been considered. Data from coastline up to 50 km offshore have been processed. Waveforms are first suitably classified and then proper retracker have been selected for the each class. High contamination zone lies from 0 to 5 km from the coast. Several retrackers such as MLE, Beta Retracker, ICE-1, ICE-2 and threshold retracking methods have been used for this purpose. Water vapour corrections are applied from the high resolution atmospheric model outputs. Similarly sea state bias also has been computed using high resolution wave model outputs. Finally, spatial filtering and averaging on the derived SSH have been carried out to reduce the noise in 40-Hz along track data. Derived SSH were then compared with tide gauge data. Detailed results will be presented at the workshop.
Rashmi Sharma