High Resolution 3D Velocity Field Reconstruction from Satellite Sea Surface Temperature Observations (MED 3D),

Budget: 131890

Ocean currents are a key element in understanding many oceanic and climatic phenomena, and knowledge of them is crucial for navigation and operational applications. Therefore, a key problem in oceanography is the estimation of the synoptic 3D velocity field, which is currently only available from expensive and labor-intensive in situ measurements. Currently, altimeter measurements allow us to reconstruct the 2D velocity field of the ocean's surface with resolutions of the order of 100-150 km. However, sea surface temperature (SST) observations in the infrared spectrum have shown the ocean is very active at scales between 10 and 100 km. At present it is very difficult to extract surface velocities at these scales and it is impossible to access vertical velocities. However, recent advances in our understanding of upper layer ocean dynamics suggest that these can be modeled with an effective version of the Surface Quasi-Geostrophic (eSQG) equations.

The validity of this approach means that in situations where the SST anomaly is representative of the density anomaly below the mixed layer, the stream function and density anomaly can be reconstructed for the first 300-500 m with resolutions of 10 km from a single SST image. Then, the quasi-geostrophic vertical velocity can be diagnosed from these fields. The Mediterranean is an area that could benefit significantly from the use of SST imagery to study the surface circulation at scales below 100 km. On the one hand, the percentage of pixels without clouds is quite high. On the other hand, an important part of the mesoscale dynamics is not readily observable with existing altimeters since the Rossby radius of deformation is 10-15 km. Furthermore, Mediterranean circulation has been identified as a potentially important element in improving seasonal forecasting in the area.

The MED3D project is exclusively carried out by IC3 researchers that investigate conditions where the eSQG approximation can be used to recover the velocity field in the Mediterranean. They also study how to improve the ability to reconstruct the horizontal velocity field and validate it with in situ and satellite data, and propose to investigate the reconstruction of vertical velocities. Finally, they propose to use these techniques to recover the eddy kinetic energy and vorticity variance from SST data available from the AVHRR Pathfinder database, and to study their spatial and temporal variability.

Nationally funded project: Sustainability and Innovation, Ministry of Science and Innovation