1. Estuarine Salinity Inversion Using Acoustic Doppler Velocimetry (ADV): Methodology, Sensitivity and Environmental Modulations
关键词Tags: backscattering backscattering
摘要：从声学反向散射信号中检索水柱的水物理特性对于在河口环境中获得连续和非侵入性的观测至关重要。本研究利用声学多普勒测速仪 (ADV) 中的脉冲相干技术，提出了一种通过集成同步温度和压力数据集来估计河口水域平滑低频实际盐度的方法。实验室校准实验表明，Medwin 公式在 0 至 35 PSU 的盐度范围内实现了最高的反演精度，尽管当盐度降至 15 PSU 以下时数据离散度增加。使用现场数据进一步验证了该方法，其中通过多探头空间平均和二次多项式拟合得出声强度分布。 现场应用结果表明，300分钟移动平均滤波器从湍流噪声中提取低频盐侵入趋势，使框架能够以±3的低通趋势精度跟踪潮汐尺度盐度变化。 07 PSU 相对于参考仪器，而原始未滤波反演的均方根误差 (RMSE) 为 5. 68 PSU。反演性能对环境动态敏感：最低的误差偏差发生在以 0. 10–0. 0. 10–0. 的电流速度为特征的中等环境窗口内。 58 m/s，浊度 109. 7–208. 0 台大。相反，在流速较高（高达 0. 83 m/s）和严重浑浊（高达 278. 1 NTU）期间或在水流流速低于 0. 10 m/s 的静水期（其中声学反向散射降至 90 dB 以下），不确定性会增加。 这些发现定量地定义了声学盐度估算的环境限制，为恢复动态河口的低频盐度趋势提供了低成本和非侵入性的方法框架。
Abstract: Retrieving the hydrophysical properties of water columns from acoustic backscatter signals is crucial for obtaining continuous and nonintrusive observations in estuarine environments. Utilizing the pulse coherent technology in the Acoustic Doppler Velocimeter (ADV), this study presents a methodology to estimate smoothed, low-frequency practical salinity in estuarine waters by integrating synchronized temperature and pressure datasets. Laboratory calibration experiments demonstrate that the Medwin formula achieves the highest inversion accuracy across a salinity range of 0 to 35 PSU, although data dispersion increases when salinity drops below 15 PSU. This methodology was further validated using field data, where acoustic intensity profiles were derived through multi-probe spatial averaging and quadratic polynomial fitting. Field application results show that a 300 min moving average filter extracts the lower frequency salt intrusion trend from turbulent noise, allowing the framework to track tidal-scale salinity variations with a low pass trend precision of ±3.07 PSU relative to reference instruments, whereas the raw unfiltered inversion exhibits a root-mean-square error (RMSE) of 5.68 PSU. The inversion performance is sensitive to ambient dynamics: the lowest error deviations occur within a moderate environmental window characterized by current velocities of 0.10–0.58 m/s and turbidities of 109.7–208.0 NTU. In contrast, the uncertainty increases during periods with higher velocities (up to 0.83 m/s) and severe turbidities (up to 278.1 NTU) or during slack water periods with current velocities below 0.10 m/s where the acoustic backscatter drops below 90 dB. These findings quantitatively define the environmental constraints for acoustic salinity estimations, providing a low-cost and non-intrusive methodological framework for recovering low-frequency salinity trends in dynamic estuaries.