TY - JOUR T1 - Impact of multiple altimeter data and mean dynamic topography in a global analysis and forecasting system A1 - Hamon,Mathieu A1 - Greiner,Eric A1 - Le Traon,Pierre-Yves A1 - Remy,Elisabeth AD - Mercator Ocean, Parc Technologique du Canal, Ramonville-Saint-Agne, France AD - CLS, Ramonville-Saint-Agne, France AD - Ifremer, Plouzané, France UR - https://archimer.ifremer.fr/doc/00502/61389/ DO - 10.1175/JTECH-D-18-0236.1 KW - Ocean KW - Sea level KW - Remote sensing KW - Forecast verification KW - skill KW - Operational forecasting KW - General circulation models N2 - Satellite altimetry is one of the main sources of information used to constrain global ocean analysis and forecasting systems. In addition to in situ vertical temperature and salinity profiles, and Sea Surface Temperature (SST) data, Sea Level Anomalies (SLA) from multiple altimeters are assimilated through the knowledge of a surface reference, the Mean Dynamic Topography (MDT). The quality of analyses and forecasts mainly depends on the availability of SLA observations and on the accuracy of the MDT. A series of Observing System Evaluations (OSEs) were conducted to assess the relative importance of the number of assimilated altimeters and the accuracy of the MDT in a Mercator Ocean global ¼° ocean data assimilation system. Dedicated tools were used to quantify impacts on analyzed and forecast sea surface height, and temperature/salinity in deeper layers. The study shows that a constellation of four altimeters associated with a precise MDT is required to adequately describe and predict upper ocean circulation in a global ¼° ocean data assimilation system. Compared to a 1-altimeter configuration, a 4-altimeter configuration reduces the mean forecast error by about 30%, but the reduction can reach more than 80% in Western Boundary Current (WBC) regions. The use of the most recent MDT updates improves the accuracy of analyses and forecasts to the same extent as assimilating a fourth altimeter. Y1 - 2019/07 PB - American Meteorological Society JF - Journal Of Atmospheric And Oceanic Technology SN - 0739-0572 VL - 36 IS - 7 SP - 1255 EP - 1266 ID - 61389 ER -