Abstract
The continuous sensing of water parameters is of great importance to the study of dynamic processes in the ocean, coastal areas, and inland waters. Conventional fixed-point and ship-based observing systems cannot provide sufficient sampling of rapidly varying processes, especially for small-scale phenomena. Acoustic tomography can achieve the sensing of water parameter variations over time by continuously using sound wave propagation information. A multi-station acoustic tomography experiment was carried out in a reservoir with three sound stations for water temperature observation. Specifically, multi-path propagation sound waves were identified with ray tracing using high-precision topography data obtained with ship-mounted ADCP. A new grid inverse method is proposed in this paper for water temperature profiling along a vertical slice. The progression of water temperature variation in three vertical slices between acoustic stations was mapped by solving an inverse problem. The reliability and adaptability of the grid method developed in this research are verified by comparison with layer-averaged water temperature results. The grid method can be further developed for the 3D mapping of water parameters over time, especially in small-scale water areas, where sufficient multi-path propagation sound waves can be obtained.
Highlights
Water temperature observation is essential for the study of physical and ecological processes [1,2]
Ocean acoustic tomography (OAT), proposed by Munk and Wunsch in 1979 [6], is an advanced oceanographic sensing technology that can make a simultaneous mapping of time-varying subsurface structures such as current velocity, water temperature, and sound speed using an underwater sound channel [7,8,9]
Supposing that sound waves propagate in an underwater environment, the structures of the sound rays are shown in Figure 1 with a given sound speed profile
Summary
Water temperature observation is essential for the study of physical and ecological processes [1,2]. It is difficult to use conventional observation methods such as fixed temperature depth chains (TD) and thermocouples for long-term and high-precision synchronous sensing in large areas of water [5], which seriously limits the development of related scientific research. Ocean acoustic tomography (OAT), proposed by Munk and Wunsch in 1979 [6], is an advanced oceanographic sensing technology that can make a simultaneous mapping of time-varying subsurface structures such as current velocity, water temperature, and sound speed using an underwater sound channel [7,8,9]. Coastal acoustic tomography (CAT) was further developed for water parameter observation in coastal areas. The issue of temperature observation in small-scale waters such as lakes, reservoirs, and artificial
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