AN APPROACH TO THE INVERSION OF INTERNAL WAVE PARAMETERS

Abstract: Due to the large deviation of sound speed fields caused by internal waves, the sound propagation through this range-dependent medium induces an energy exchange between different acoustic normal modes. Two kinds of methods are proposed to reconstruct the internal solitary wave (ISW) parameters: phase speed and wavelength. First, in case of internal waves moving between an acoustic source and receiver, the time series of the mode amplitude behave like some quasi-period phenomena, and the periods are described as a product of the ISW moving-speed and the difference of normal mode wave number. The ISW speed is inverted by means of the spectrum analysis of the time series of mode amplitude. Second, the mode coupling only occurs when the wave number difference between the two coupling modes is equal to the wave number of the ISW spectrum, serving to estimate the ISW wavelength. The simulation is performed to evaluate the above inversion methods, setting an internal solitary wave or an internal solitary wave packet in the simulation domain. The inversion errors due to the wave phase speed are about 5 % and 10 % for the flat and slope topographies, respectively. The lower the sound frequency, the more accurate the inversion result. When the suitable resonance frequency is adopted, the inversion errors of wavelength are smaller than 10%. The inversion error is increased with the increasing amplitude of internal solitons, also the error is changed with the number of solitons included in the packet