Knowledge of the water-column temperature profile is critical to acoustic and optical sensor performance, yet acquiring it currently requires deploying point sensors into the water — an operation that costs time, consumes expendables, and may not be possible from all platforms. Raman LiDAR offers an alternative: non-contact, range-resolved temperature retrieval from airborne, surface or submerged platforms. We present the development and validation of such a method, covering laboratory demonstration at better than 0.5 °C accuracy over a 50 m range through to field measurements in ​open ocean environments.
The central challenge is that the temperature-sensitive Raman return from water is never measured in isolation. In natural waters, absorption, elastic scattering, fluorescence and spatially varying optical properties all modify the detected signal and can bias the retrieved temperature if left unaccounted for. We describe the calibration and validation approach in detail, including range-resolved measurements, spectral channel analysis and comparison against co-located reference sensors. Controlled test-water results confirm sub-0.5 °C retrieval accuracy at operationally relevant standoff distances. Field measurements are then used to demonstrate that corrections for absorption and fluorescence are essential to isolate the temperature-dependent return from competing spectral contributions — and to identify the water conditions under which the technique remains robust.
The results trace a clear pathway from laboratory validation to practical water-column remote sensing, with performance limits governed by signal-to-noise ratio, water clarity, background fluorescence and calibration stability. The broader implication is an active optical sensing capability for standoff water-column characterisation, with relevance to undersea situational awareness and environmental assessment.