E. De Marinis demarinis@dune-sistemi.com
Dune, Roma, Italy
A. Crise crise@andy.ogs.trieste.it
OGS, Trieste, Italy
O. Gasparini gasparini@dune-sistemi.com
Dune, Roma, Italy
S.M. Jesus sjesus@ualg.pt
SiPLAB-FCT, Universidade do Algarve
PT-8000 Faro, Portugal
P. Picco paola.picco@santateresa.enea.it
ENEA - CRAM, La Spezia, Italy
S. Salon salon@andy.ogs.trieste.it
OGS, Trieste, Italy
Comments:
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Ref.: in EGS-AGU-EUG Joint Assembly, Geophysical
Research Abstracts, vol. 5,
01211, European Geophysical Society, Nice, France, 2003.
Abstract : INTIMATE’00 (Internal Tide Measurements with Acoustic
Tomography Experiments) and TOMPACO (TOMografia PAssiva COstiera)
projects developed and tested on real data a new sea temperature
acoustic tomographic methodology relying on the noise emitted from
ships of opportunity as sound source. The experimental campaign took
place on October 2000 in the Atlantic Ocean in front of the Portuguese
coasts, in an acoustically shallow water area where internal tides
regularly occur, leading to a significant variability of the thermal
structure. The passive tomography experiments were carried out with a
co-operative vessel (NRP Don Carlos I from the Hydrographic Institute
of Portugal), with oceanographic conditions in the experimental area
monitored both by fixed moorings (currentmeters, CTD, thermistor
chains) and by XBTs. Both pseudorandom noise sequences from a towed
projector and the radiated ship noise were used as sound sources for
the tomographic inversion; a 16 elements array was used as sound
receiver. In the flat bottom region (range-independent case) and with a
constant speed of the vessel (about 9kn), the tomographic inversion
process applied to the received sound signals achieved a quite
satisfactory reconstruction of the vertical temperature profile in the
area. The quality of the results was increased by an appropriate
pre-processing of the crossspectral matrix of the ship radiated noise
and by a smooth selection of the frequency bins for the inversion; the
use of genetic algorithm allowed an efficient solution search in the
huge volume of the unknown parameters to be inverted. Results
demonstrate that this methodology can be effectively exploited for the
remote, long term monitoring of temperature profile variability in wide
oceanic areas.
ACKNOWLEDGMENT: this work was partially supported by ATOMS
project from FCT (Portugal) and TOMPACO project (CNR-Italy).