Analysis of Internal Wave Signatures in X-Band Marine Radar Images

Abstract

This research aims to discuss and validate the presence of internal wave signatures in sea surface radar backscatter images using a dataset collected by a shipboard X-Band radar and a vessel-mounted ADCP in equatorial waters. The internal wave event occurred on 19th May 2022 between 10:38-11:00 UTC when the research vessel Meteor (M181 TRATLEQ II cruise) was moving towards Brazilian waters reaching latitudes of about 0◦0′ S and longitudes from 42◦20.73′ W to 42◦26.06′ W. The nautical radar onboard also reported this event and we identify some backscatter features from internal waves even in the individual raw-radar images. The internal waves are also detected in composite images of sea surface radar backscatter images and near-surface wave current maps. The radar-derived wave current vectors are computed through an iterative procedure based on filtering the energy of the dispersion relationship to enhance the signal-to-noise ratio of predictions. We observe variations in wave current vectors when interacting with internal wave signatures. Finally, in-situ velocity data from a vessel-mounted ADCP validates the presence of internal waves during the analysis period, where vertical displacements occur in zonal and meridional velocities between 100-600 m water depth. Hence, results suggest shipboard X-Band radars are able to detect internal wave features at sea surface under special conditions.