Real-Time Observation of Range-Averaged Temperature by High-Frequency Underwater Acoustic Thermometry

Temperature has a great impact on the underwater environment in oceans. The real-time monitoring of it is of both scientific and practical importance. In this paper, we proposed a new scheme of high-frequency acoustic thermometry to measure the real-time ranged-averaged underwater temperature. The cross-correlation analysis with high-resolution Global Positioning System synchronization was used to derive the propagation time of underwater acoustic signals. Reciprocal underwater acoustic transmissions between two acoustic stations extracted the range-averaged temperature. Furthermore, a field experiment of high-frequency acoustic transmission was performed in the Jiulong River estuary. The ranged-average temperature extracted by the underwater acoustic sensor was compared with in situ temperature with a relative standard deviation of about 6%. The range-averaged temperature was correlated with in situ temperature (R-2 = 0.93) during 48-hour real-time measurement experiments. The results suggest the potential applications of proposed high-frequency acoustic thermometry in real-time monitoring of the averaged temperature in coastal oceans.