Assessing the capability of three different altimetry satellite missions to observe the Northern Current by using a high-resolution model

Abstract. Over the last 3 decades, satellite altimetry has observed sea surface height variations, providing a regular monitoring of ocean circulation. Altimetry measurements have an intrinsic signal-to-noise ratio that limits spatial scales currents can be captured. However, recent progress made on both sensors and data processing allows us to observe smaller geophysical signals, offering new perspectives in coastal areas where these structures are important. In this methodological study, we assess ability three altimeter missions with different technologies capture Northern Current (northwestern Mediterranean Sea) its variability, namely Jason-2 (Ku-band low-resolution-mode altimeter, launched 2008), SARAL/AltiKa (Ka-band 2013) Sentinel-3A (synthetic aperture radar 2016). Therefore, use high-resolution regional model as reference. We focus along French coast Provence, first show is very close observations high-frequency radars gliders terms current estimates. model, 15–20 km from average, mean core velocity 0.39 m s−1. Its signature level consists drop whose value at 6.14∘ E 6.9 cm, extending over 20 km. These variations clear seasonal pattern, but signals also present most time. comparison, 1 Hz data, associated overestimated by 3.0 cm for Jason-2, overestimation significantly less (0.3 1.4 respectively). corresponding SARAL estimates larger than reference (+1.3 +1 respectively), whereas shows closer values (−0.4 cm). When derive geostrophic without any filtering, comparison standard deviations one mission other (3.7 times too large 2.4 2.9 low-pass filtering cutoff wavelengths, best agreement between distributions obtained 60, 30 40–50 wavelength respectively. This study using not only illustrate how advances performances altimeters improve observation quantify gain.