remote sensing Article Evaluation of Coastal Sea Level Offshore Hong Kong from Jason-2 Altimetry Xi-Yu Xu 1,2,3,*, Florence Birol 2 and Anny Cazenave 2,4 1 The CAS Key Laboratory of Microwave Remote Sensing, National Space Science Center, Chinese Academy of Sciences, Beijing 100190, China 2 Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (LEGOS), Observatoire Midi-Pyrénées, 31400 Toulouse, France; fl
[email protected] (F.B.);
[email protected] (A.C.) 3 State Key Laboratory of Remote Sensing Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China 4 International Space Science Institute, 3102 Bern, Switzerland * Correspondence:
[email protected]; Tel.: +86-10-6255-0409 Received: 23 November 2017; Accepted: 6 February 2018; Published: 12 February 2018 Abstract: As altimeter satellites approach coastal areas, the number of valid sea surface height measurements decrease dramatically because of land contamination. In recent years, different methodologies have been developed to recover data within 10–20 km from the coast. These include computation of geophysical corrections adapted to the coastal zone and retracking of raw radar echoes. In this paper, we combine for the first time coastal geophysical corrections and retracking along a Jason-2 satellite pass that crosses the coast near the Hong-Kong tide gauge. Six years and a half of data are analyzed, from July 2008 to December 2014 (orbital cycles 1–238). Different retrackers are considered, including the ALES retracker and the different retrackers of the PISTACH products. For each retracker, we evaluate the quality of the recovered sea surface height by comparing with data from the Hong Kong tide gauge (located 10 km away).