TOMOGRAPHIC INVERSION OF THE EL-NINO PROFILE BY USING A MATCHED-MODE PROCESSING (MMP) METHOD

A high-resolution mode-matching (HRMM) estimator is used to invert El Nino profile perturbations. By matching a proper set of modal travel time perturbations in a 2-D parameter space constructed by the first two coefficients of the empirical orthogonal function (EOF), the El Nino profile can be efficiently inverted. As contrasted with the conventional linear inversion scheme, the performance of the matched-mode scheme is significantly improved because the nonlinearity of the modal travel time perturbation has been taken into account.