Impact of Assimilating SARAL/AltiKa SWH in SWAN Model During Indian Ocean Tropical Cyclone Phailin

The focus of the study is assimilation of significant wave height (SWH) obtained from first Ka-band altimeter AltiKa onboard SARAL, a collaborative mission of the Indian Space Research Organization and Centre National d'Etudes Spatiales, France. The state-of-the art coastal wave model simulating waves near-shore has been used for this purpose. The well-tested optimal interpolation technique is adopted for this assimilation. A distinguishing feature of this study is the test of this assimilation scheme with SARAL/AltiKa data during the occurrence of a recent severe Cyclone Phailin in the Indian Ocean with its associated extreme waves. Before proceeding to assimilation per se, SARAL/AltiKa SWH has been validated using in situ as well as other satellite data. Apart from validation, this intercomparison also served the purpose of providing the needed error covariance to be used in assimilation. The supremacy of an assimilation run over a parallel control run without assimilation has been judged by comparing the results with Indian Ocean buoy observations and also with Jason-2 observations. The statistics of the validation of the assimilation run has been found to be extremely encouraging.