Effects of salinity and pressure on the ocean temperature measurement by Brillouin lidar

In order to raise the accuracy of temperature measurement in the deep ocean, an empirical equation for the seawater temperature as a function of Brillouin frequency shift, salinity, and pressure was derived. The dependences of the temperature on the salinity, pressure, and Brillouin shift were quantitatively analyzed. The influences of the variation of salinity and pressure on the uncertainty of temperature measurement were also discussed. The research shows that the accuracy of temperature measurement is limited by the distributions of the salinity and pressure of the ocean. The measurement uncertainty is approximately 0.4°C. Therefore, the salinity and pressure of the measured location should be determined simultaneously in the practical measurement. Thus the temperature resolution will be increased up to 0.05°C.