Estimating background error covariance parameters and assessing their impact in the OSTIA system

The impact of updating the background error parameters in the Operational Sea surface Temperature and sea-Ice Analysis (OSTIA) was assessed. The updates improved the analysis accuracy compared to assimilated and independent reference observations. The covariance updates also improved the ability of the SST analysis to represent small-scale ocean features without introducing spurious noise. As OSTIA is used as boundary conditions in the numerical weather prediction (NWP) system at the Met Office the impact on the NWP forecasts was also assessed. The OSTIA changes were found to have a positive impact on NWP forecast skill.