Strongly Nonlinear Effects on Determining Internal Solitary Wave Parameters From Surface Signatures With Potential for Remote Sensing Applications

The inversion of remote sensing signatures of internal solitary waves (ISWs) can retrieve dynamic characteristics in the ocean interior. However, the presence of ubiquitous large-amplitude ISWs poses challenges to the commonly used weakly nonlinear methods for parameter retrieval. Through laboratory experiments, we establish a relationship between surface features and internal characteristics of ISWs by the remote sensing imaging mechanism. The results demonstrate that strong nonlinearity significantly influences the retrieval of ISWs, primarily manifested in the calculation of wave-induced velocities and the applicability of ISW solutions. A fully nonlinear model Dubreil-Jacotin-Long equation is used in the retrieval and has been tested under different conditions. Mooring observations indicate that the determination of ISW parameters from satellite images is affected by the complexity of in situ stratification, but additional remote sensing information such as surface velocities enables us to perform retrievals even if the real-time measurement of pycnocline depth is not available. Internal solitary waves (ISWs), as nonlinear internal waves, play an essential role in oceanic human activities and ocean mixing. The surface current induced by ISWs can create rough and smooth regions on the sea surface due to the modulated roughness, hence presenting alternating bright and dark stripes in satellite images. Satellites can observe ISWs over a wide range via surface manifestations, and the internal dynamics can be calculated from surface features using retrieval methods. However, the availability of retrieval methods still needs to be verified, facing the difficulty of matching mooring observations and satellite images of the same ISW in a short time interval. According to the proportional relation of remote sensing signatures and wave-induced velocities, this study establishes the relationship between surface features and internal characteristics of ISWs in laboratory experiments. Strong nonlinearity significantly influences the retrieval of ISWs and a fully nonlinear model is well applied in retrieval. Then we test the retrieval in oceanic environments, mooring observations show the critical role of stratification in retrieval. This work provides a reliable dynamics model for the inversion of remote sensing signatures of ISWs into characteristics in the ocean interior. The relationship between surface features and internal parameters of internal solitary waves is established in laboratory experimentsStrong nonlinearity significantly impacts the determination of wave parameters from the surface. A fully nonlinear model is well appliedAccurate parameter determination is constrained by the complex oceanic stratification, but more remote sensing information can overcome it