Exploitable results Comparisons of three approaches to the ocean-acoustic tomography: field experiment and numerical simulations The project was aimed at creation of experimental database for adequate comparison of three approaches to the ocean acoustic tomography: conventional technique with moored transceivers, Moving Ship Tomography (MOST), when the signals are emitted or recorded by a mobile R/V surveying the area under study, and Matched Field Tomography with long vertical arrays. Seven transceivers were moored in the Western Mediterranean basin in early 1994 in the framework of the THETIS-2 project, carried out in conventional technique by IfM (Kiel, Germany), IFREMER (Brest, France) and WHOI (Woods Hole, U.S.A.). These transceivers also served as broad-band sound sources for MOST and Matched Field tomography experiments. During the field expedition on board the R/V "Akademik Sergey Vavilov" of the Russian Academy of Sciences four tomographic surveys of the basin were completed: -MOST Experiment - acoustic receptions were carried out using a single hydrophone deployed from the R/V in drift. Observation points were chosen along existing propagation paths of the THETIS-2 network. -A survey of a Cold Mesoscale Eddy - the CTD casts and receptions with a single hydrophone were focused on the area of the inhomogeneity to study the ability of different approaches to resolve mesoscale ocean structure. -An experiment with the Multi-Element Modular Array - the receptions were carried out using a ship-borne vertical array. -A survey with Autonomous Bottom Stations (ABS), equippped with multi vertical arrays. A total of 73 R/V stations for acoustical measurements and 9 ABS installations were done and over 400 individual transmissions from the different sources were recorded. An independent database of 157 direct CTD cast was collected to initiate the inversion and verify its results. A special data-processing technique was developed for precise compensation of the Doppler effect due to R/V drift, estimated with 0.5-1.0 cm/s accuracy. In more than 80% of receptions the processing revealed stable arrival patterns with good SNR and multiple resolvable ray (at distances over 300km also modal) arrivals up to 400-600 km range for different sources. An innovative inversion approach based on matching the overall arrival pattern was proposed and compared with the traditional linear scheme. Tomographic inversion was done for 2 sections in the northern and suthern parts of the basin. The reconstructed 2D sound speed fields in these vertical slices proved to be in good agreements with independent oceanographic measurements. Comparison of inversion results for June and July parts of the MOST experiment demonstrated the temporal changes of the medium were successfully measured in the moving ship approach. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
