Investigation on inversion method of ocean salinity based on high spectra resolution lidar

Salinity is one of the important physical parameters in oceanography. Current methods for remote sensing of ocean salinity are based on the monotropic function between Raman spectra and ocean salinity, while the effect of the ocean temperature, which influences the measurement of salinity, is neglected. Therefore, this paper proposes a method for fine inversion of salinity combining Brillouin and Raman spectra of water. The Raman spectra of solutions containing a single solute and mixed solutions were detected, and the effect of solutions containing different solutes on the spectra was analyzed. The experimental results revealed the variation in the low- and high-frequency spectral intensities of the Raman spectra with salinity and temperature. The Raman spectra of seawater were modeled as a function of temperature and salinity using the low- and high-frequency area ratios. Brillouin scattering spectra are also related to ocean temperature and salinity, changes in temperature and salinity will affect the frequency shift and line-width of Brillouin scattering spectra. Based on the Brillouin scattering theory, the relationship between frequency shift and line-width with ocean temperature and salinity was analyzed. With high spectra resolution lidar as the detection technique, the Brillouin frequency shift, line-width and Raman spectra of ocean could be detected simultaneously by using multi-beam interferometry, photon correlation spectroscopy, and Raman spectra detection techniques. A high precision inversion model of ocean salinity can be obtained by using a multi-source data fusion. This research will provide reliable data for the study of global climates and ecosystems and improve the accuracy of marine disaster warnings and marine weather forecasting.