Satellite altimetry provides essential sea level observations to constrain ocean analysis and forecasting systems. New generation of nadir altimeters now provides enhanced capability thanks to a SAR mode that allows reducing the 1 Hz (7 km) measurement noise level from about 3 to 1 cm RMS. A first assessment of the impact of SAR altimetry for global ocean analysis and forecasting is carried out using Observing System Simulation Experiments (OSSEs) with the global Mercator Ocean high resolution 1/12° system. OSSEs are used to quantify the impact of assimilating multiple altimeter missions with and without a SAR mode. A simple twin experiment set up that only takes into account initialisation errors and impact of altimeter random noise is used. Results are analysed in high eddy energy regions where initialisation errors are the most important ones. Both sea surface height and surface velocity analyses and 7-day forecasts are improved. Compared to conventional altimetry, SAR altimetry sea surface height variance errors for both analyses and forecasts are typically reduced by 20% in western boundary currents. This suggests that use of SAR multiple altimeter missions with high-resolution models will significantly improve the capability of the ocean analysis and forecasting systems in the near future.

卫星测高仪提供必要的海平面观测值，以限制海洋分析和预报系统。SAR模式可以将1 Hz（7 km）的测量噪声水平从3 RMS降低到1 cm RMS，现在新一代天底高度计可提供增强的功能。SAR测高仪对全球海洋分析和预报的影响的首次评估是使用观测系统模拟实验（OSSE）和全球Mercator Ocean高分辨率1/12°系统进行的。OSSE用于量化使用和不使用SAR模式时同化多个高度计任务的影响。使用简单的双实验设置，仅考虑初始化误差和高度计随机噪声的影响。在初始化误差最重要的高涡能量区域分析结果。海面高度和表面速度分析以及7天预报都得到了改善。与常规测高相比，在分析和预报方面，SAR测高海平面高度方差误差在西方边界流中通常减少了20％。这表明在不久的将来将SAR多高度计任务与高分辨率模型一起使用将大大提高海洋分析和预报系统的能力。