From Multi-Sensor Tracking of Sea Surface Films to Mesoscale and Sub-Mesoscale Sea Surface Current Fields

摘要

The knowledge about mesoscale and sub-mesoscale sea surface current fields is of high interdisciplinary interest, since it results in a better understanding of ocean-atmosphere interactions. However, many available numerical model results are of resolutions, which are too coarse to investigate mesoscale and sub-mesoscale turbulent features like eddies, particularly in coastal waters. In this work we present the results of tracking biogenic and anthropogenic surface film signatures on multi-sensor satellite images (SAR and multispectral images) to estimate the local sea surface current field. The main advantage of this approach is that the resolution of the derived current fields depends mainly on the resolution of the images, which have been used for tracking. Due to the large temporal distance between two acquisitions of a scene and the high variability of the tracked sea surface films, classical tracking methods, e.g. feature based or Optical Flow methods may not be applicable to successfully track the imaged signatures of the surface films. In this work, we use our former developed generic framework, which ensures the applicability and increases the stability of the results for well-known tracking and Optical Flow algorithms. With this framework, it is e.g. possible to compute the sea surface current field using Optical Flow approaches even for large spatiotemporal distances and with partial scene coverage. We present and compare the results of different tracking algorithms by means of tracking biogenic sea surface films. The investigated areas are the Baltic Sea and the Black Sea. We present the use of Landsat TM, SeaWiFS, ERS-2, TerraSAR-X and RADARSAT-2 data for the derivation of sea surface currents. The resolution of the images used varies from moderate to fine resolution, which allows the derivation sea surface current fields of moderate to fine resolutions.