Towards high-resolution mapping of ocean dynamics: multiscale fusion between low-resolution altimetry and high resolution sst
Résumé
Two different products have been developed based on gridded satellite data. The first one at low resolution is calculated from a combination of satellite absolute dynamic topography geostrophic currents, and blended wind driven currents following the methodology initially proposed by Sudre and Morrow (2008) [1]. An upgraded version of this approach has been developed recently including: the precise consideration of the equatorial singularity through the semi-geosptrophic methodology (which is also derived from the absolute dynamic topography), and a variable wind mixing depth as a function of latitude for the wind driven currents [2]. The second ocean dynamics product at high resolution is established using a radically new method. It is based on an approximation of the energy cascade, expressed in a microcanonical formulation, and associated to turbulent signal provided by SST MODIS-Aqua product at 1/24°. The basic idea is to use optimal cascading to decrease the spatial resolution of SST MODIS-Aqua product at 1/24°, then use the motion information available at lower resolution coming from the first product described above, transmit that information along the scales back to higher spatial resolution using the cascade to obtain a 1/24° resolution motion field [3]. [1] J. Sudre and R. A. Morrow, 2008. Global surface currents: a high-resolution product for investigating ocean dynamics, Ocean Dynamics, vol. 58, DOI 10.1007/s10236-008-0134-9. [2] J. Sudre and C. Maes, in prep. [3] H. Yahia, J. Sudre, C. Pottier and V. Garçon, 2010, Motion analysis in oceanographic satellite images using multiscale methods and the energy cascade, Pattern Recognition, DOI: 10.1016/J.patcog.2010.04.011.