Xu Ning, Liu Zhiqiang, Zhang Xianda, Xu Yupeng, Luo Ningning, Li Shujing, Xu Jinjun, He Xingdao, Shi Jiulin
Opt Express. 2021 Oct 25;29(22):36442-36452. doi: 10.1364/OE.443151.
Brillouin-based LiDAR is an alternative remote sensing technique for measuring the distribution profiles of temperature, salinity, and sound speed in the upper ocean mixed layer. Its principle is based on the dependence of Brillouin frequency shift on the temperature, salinity, and depth of ocean. Therefore, it is necessary to investigate the effect of various seawater parameters on Brillouin frequency shift for ocean remote sensing by using the Brillouin LiDAR. Here we theoretically and experimentally investigate the influence of temperature, salinity, and pressure (depth) of seawater on Brillouin frequency shift in the upper ocean for the first time. Numerical simulations of the distribution profiles of temperature, salinity, and Brillouin frequency shift in the upper-ocean mixed layers of East China Sea and South China Sea were performed, respectively, by employing the Brillouin equations and the World Ocean Atlas 2018 (WOA18). A special ocean simulation system was designed to carry out the stimulated Brillouin scattering (SBS) experiments for validating the numerical simulations. The results show that the seawater temperature is the most important factor for the Brillouin frequency shift in the upper-ocean mixed layer compared with the salinity and pressure. At the same salinity and pressure, the frequency shift increases by more than 10 MHz for every 1 °C increase in temperature. Also, the differences of Brillouin frequency shift between experimental and theoretical values at the same parameter conditions were analyzed. The experimental results coincide well with the theoretical simulations. This work is essential to future applications of Brillouin LiDAR in remote sensing of the temperature, salinity, or sound velocity profiles of ocean.
基于布里渊散射的激光雷达是一种用于测量海洋上层混合层温度、盐度和声速分布剖面的遥感技术。其原理基于布里渊频移对海洋温度、盐度和深度的依赖性。因此，有必要通过布里渊激光雷达研究各种海水参数对海洋遥感中布里渊频移的影响。在此，我们首次从理论和实验上研究了海水温度、盐度和压力（深度）对海洋上层布里渊频移的影响。分别利用布里渊方程和《2018年世界海洋图集》（WOA18）对东海和南海海洋上层混合层的温度、盐度和布里渊频移分布剖面进行了数值模拟。设计了一个特殊的海洋模拟系统来进行受激布里渊散射（SBS）实验，以验证数值模拟结果。结果表明，与盐度和压力相比，海水温度是海洋上层混合层中布里渊频移的最重要因素。在相同盐度和压力下，温度每升高1℃，频移增加超过10 MHz。此外，还分析了相同参数条件下实验值与理论值之间布里渊频移的差异。实验结果与理论模拟结果吻合良好。这项工作对于布里渊激光雷达未来在海洋温度、盐度或声速剖面遥感中的应用至关重要。
