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Temperature reconstruction errors caused by representation of a priori information with use empirical ortogonal functions

Virovlyansky A. L., Kazarova A. Y., Lyubavin L. Y., Stromkov A A.

Hydroacoustics

2000

Vol. 3

105--108

The restoration of mean temperature of water layer is considered when the expansion of inhomogeneities of temperature field on empirical orthogonal functions (EOF) is used for description of a priori information. In practice only several first EOF giving the basic contribution into average square of a sound speed variation are taken into account. Even small modification of statistical model of inhomogeneities can noticeably change for the worse the quality of restoration of parameters of inhomogeneities. It is shown that the neglect by higher EOF, despite of their rather small contribution, can noticeably increase an error of the restoration of mean temperature of water layer.

Identification of rays in a signal registered from the drifting ship

Stromkov A. A., Kazarova A. Y., Virovlyansky A. L., Lyubavin L. Y.

Hydroacoustics

1999

Vol. 2

313--316

Possibilities of ray identification in the ship tomography experiment in Western Mediterranean are discussed. The pulse signals (M-sequences) emitted by the stationary source located at the axis of the subsurface acoustic waveguide (the axis depth was 125 m) were registered from the board of the drifting shift. Frequency Doppler shift was compensated. It is shown that in the signal registered by a single hydrophone, depending on the hydrophone depth, arrivals of fours rays with steep grazing angles (at small depths), arrivals of pair or arrivals of individual rays (at greater depths) can be resolved: Due to the drift the distance between the source and receiver was always known with some error. In spite of this fact the measured differences in ray travel times and in travel times of fours of rays were in good agreement with the theoretical predictions obtained using a ray code.