Estimation of Surface Geostrophic Currents from SAR Altimetry
Martin-Puig, Cristina¹; Isern-Fontanet, Jordi²; González-Haro, Cristina^2
1isardSAT, SPAIN; ²Institut Catalŕ de Cičncies del Clima, SPAIN

High-resolution Ocean surface currents are crucial for security, transport and energy industries. The observation of these phenomena at mesoscale (10-50km) and sub-mesoscale (<10km) is already feasible thanks to a few Earth Observation technologies, one of them conventional altimetry. The understanding of Ocean circulation at smaller scales is a pursued scientific goal provided it should allow for the identification of new features and the quantification of their impact on sub- and mesoscale ocean circulation, but still remains a challenge for conventional altimetry. The along-track sampling geometry, spatial resolution and noise level strongly limits conventional altimetry effective resolution to scales of a few tens of km. With the new altimetric mode provided for the first time by CryoSat-2 (CS-2): the Synthetic Aperture Radar (SAR) Mode (SARM); along-track resolution is considerably enhanced, so should be the signal to noise ratio (SNR), as a result of the application of Delay-Doppler techniques (including multi-look) to conventional altimetry. Therefore, at least along-track, we shall expect that this new altimetric mode may offer us the possibility to enhance Ocean surface currents mapping.

This paper aims at providing an initial study focused on investigating the potentialities of the SAR mode for the derivation of geostrophic currents. For this we will concentrate our observations on the Mediterranean Sea and compare the results derived from CS-2 SARM to those achieved historically with conventional altimetry from other missions coincident in time with CS-2. We will concentrate mainly in the quantification of the noise level and its impact in the derivation of ocean currents. Providing a first assessment of the effective currents resolution, which shall be derived from the new altimetric mode.