CoAuthors

Rashmi Sharma (ISRO, India); Neeraj Agarwal (ISRO, India); Raj Kumar (ISRO, India)

SARAL, a joint ISRO-CNES satellite mission, was successfully launched in 2013. It carries a Ka band single frequency satellite altimeter (AltiKa). Satellite altimeters are primarily used to study sea level changes. In the open ocean, the altimetric echo follows a standard shape, with steeply rising leading edge followed by a trailing edge with gradually diminishing power. This standard shape is in agreement with the theoretical Brown model and hence can be easily modeled. However, in the coastal areas, due to the presence of land and other coastal features in the footprint of the altimeter, contamination occurs and the return is different from open ocean. Up to some extent these contaminations can be modeled. Footprint size of SARAL/AltiKa is small which is ideal for coastal studies. The available ocean retracker (MLE4) itself shows good performance near the coast. However, further improvements can be achieved by using algorithms which can simulate contaminations impact in the coastal areas. In this study we have used various models for the return waveforms at 40 Hz to extract maximum information from the altimeter. Our results show that algorithms which are useful in the coastal areas are BETA5, BETA9 and Brown with Asymmetric Gaussian Peak (BAGP). In this study we demonstrate the usefulness of this dataset in depicting seasonal variability of geostrophic currents along the east coast of India. The results are validated with the available HF radar observations at few locations. Details of the analysis will be presented in the meeting.