Inversion for Time-Evolving Sound-Speed Field in a Shallow Ocean by Ensemble Kalman Filtering

In the context of the recent Maritime Rapid Environmental Assessment/Blue Planet 2007 sea trial (MREA/BP07), this paper presents a range-resolving tomography method based on ensemble Kalman filtering of full-field acoustic measurements, dedicated to the monitoring of environmental parameters in coastal waters. The inverse problem is formulated in a state-space form wherein the time-varying sound-speed field (SSF) is assumed to follow a random walk with known statistics and the acoustic measurements are a nonlinear function of the SSF and the bottom properties. The state-space form enables a straightforward implementation of a nonlinear Kalman filter, leading to a data assimilation problem. Surface measurements augment the measurement vector to constrain the range-dependent structure of the SSF. Realistic scenarios of vertical slice shallow-water tomography experiments are simulated with an oceanic model, based on the MREA/BP07 experiment. Prior geoacoustic inversion on the same location gives the bottom acoustic properties that are input to the propagation model. Simulation results show that the proposed scheme enables the continuous tracking of the range-dependent SSF parameters and their associated uncertainties assimilating new measurements each hour. It is shown that ensemble methods are required to properly manage the nonlinearity of the model. The problem of the sensitivity to the vertical array (VA) configuration is also addressed.

[1]  Peter Gerstoft,et al.  Inversion of broad-band multitone acoustic data from the YELLOW SHARK summer experiments , 1996 .

[2]  Gerassimos A. Athanassoulis,et al.  Ocean acoustic tomography based on peak arrivals , 1996 .

[3]  G. Evensen.  Data Assimilation: The Ensemble Kalman Filter , 2006 .

[4]  Jean-Pierre Hermand,et al.  Remote sensing of Tyrrhenian shallow waters using the adjoint of a full-field acoustic propagation model , 2009 .

[5]  E. J. Sullivan,et al.  Ocean acoustic signal processing: A model‐based approach , 1992 .

[6]  Michael I. Taroudakis,et al.  On the use of matched-field processing and hybrid algorithms for vertical slice tomography , 1997 .

[7]  1000-km range 2 dimensional ocean acoustic tomography near Japan , 1995, 'Challenges of Our Changing Global Environment'. Conference Proceedings. OCEANS '95 MTS/IEEE.

[8]  S. Jesus,et al.  Tracking cold water upwelling filaments in the ocean using matched-field inversion , 1993 .

[9]  Henrik Schmidt,et al.  Ocean acoustic tomography as a data assimilation problem , 2002 .

[10]  Rosalia Santoleri,et al.  Observing The Mediterranean Sea from space : 21 years of Pathfinder-AVHRR Sea Surface Temperatures ( 1985 to 2005 ) . Re-analysis and validation , 2006 .

[11]  Mark Porter,et al.  The KRAKEN normal mode program , 1992 .

[12]  T. Başar,et al.  A New Approach to Linear Filtering and Prediction Problems , 2001 .

[13]  Subramaniam Rajan,et al.  Model-oriented ocean tomography using higher frequency, bottom-mounted hydrophones. , 2005, The Journal of the Acoustical Society of America.

[14]  Walter Munk,et al.  Ocean Acoustic Tomography , 1988 .

[15]  E. J. Sullivan,et al.  Model‐based environmental inversion: A shallow water ocean application , 1995 .

[16]  J.-C. Le Gac,et al.  Subseafloor geoacoustic characterization in the kilohertz regime with a broadband source and a 4-element receiver array , 2008, OCEANS 2008.

[17]  W. Munk,et al.  Ocean Acoustic Tomograpthy: Notation , 1995 .

[18]  W. Kuperman,et al.  Computational Ocean Acoustics , 1994 .

[19]  R. B. Evans,et al.  A coupled mode solution for acoustic propagation in a waveguide with stepwise depth variations of a penetrable bottom , 1983 .

[20]  Jean-Pierre Hermand,et al.  Broad-band geoacoustic inversion in shallow water from waveguide impulse response measurements on a single hydrophone: theory and experimental results , 1999 .

[21]  Henrik Schmidt,et al.  Acoustic tomography of a coastal front in Haro Strait, British Columbia , 1999 .

[22]  Jean-Pierre Hermand,et al.  Acoustic model-based matched filter processing for fading time-dispersive ocean channels: theory and experiment , 1993 .

[23]  C. Mecklenbräuker,et al.  OBJECTIVE FUNCTIONS FOR OCEAN ACOUSTIC INVERSION DERIVED BY LIKELIHOOD METHODS , 1998 .

[24]  Pierre F. J. Lermusiaux,et al.  Four-Dimensional Data Assimilation for Coupled Physical-Acoustical Fields , 2002 .

[25]  Peter Gerstoft,et al.  Parameter estimation using multifrequency range‐dependent acoustic data in shallow water , 1996 .

[26]  Arata Kaneko,et al.  Assimilation of coastal acoustic tomography data into a barotropic ocean model , 2000 .

[27]  Michel Rixen,et al.  Full-field tomography and Kalman tracking of the range-dependent sound speed field in a coastal water environment , 2009 .

[28]  Jean-Claude Le Gac,et al.  High-frequency multibeam echosounder classification for rapid environmental assessment , 2008 .

[29]  Jeffrey K. Uhlmann,et al.  New extension of the Kalman filter to nonlinear systems , 1997, Defense, Security, and Sensing.

[30]  Michael I. Taroudakis,et al.  A MODAL INVERSION SCHEME FOR OCEAN ACOUSTIC TOMOGRAPHY , 1993 .

[31]  Clark Rowley,et al.  A Note on NCOM Temperature Forecast Error Calibration Using the Ensemble Transform , 2009 .

[32]  F. Middleton,et al.  An underwater acoustic sound velocity data model , 1980 .

[33]  M. Berrada,et al.  Adjoint-based acoustic inversion for the physical characterization of a shallow water environment , 2006 .

[34]  Carl Wunsch,et al.  Ocean acoustic tomography: a scheme for large scale monitoring , 1979 .

[35]  Rainer Storn,et al.  Differential Evolution – A Simple and Efficient Heuristic for global Optimization over Continuous Spaces , 1997, J. Glob. Optim..

[36]  James V. Candy,et al.  Model-Based Signal Processing , 1985 .

[37]  T. Birdsall,et al.  Tomographic Maps of the Ocean Mesoscale. Part 1: Pure Acoustics , 1985 .

[38]  S. Dosso,et al.  Quantifying uncertainty in geoacoustic inversion. II. Application to broadband, shallow-water data. , 2002, The Journal of the Acoustical Society of America.