Ocean Model Analysis and Prediction System version 4.1i (OceanMAPSv4p1i)

Abstract. The Ocean Model Analysis and Prediction System (OceanMAPS) is a short-range, near-global, eddy-resolving ocean forecasting system developed at the Bureau of Meteorology. OceanMAPS runs daily, producing 7-day forecasts of 3D prognostic fields of ocean currents, temperature, salinity and sea level anomalies (SLA’s). OceanMAPS is based on MOM5 ocean general circulation model and uses EnKF-C software for data assimilation. Consistent with the previous version of OceanMAPS, version v4p1i (OceanMAPSv4p1i), is based on a hybrid Ensemble Kalman Filter with 48 dynamic and 144 static members. However, OceanMAPSv4p1i employs a 1-day analysis cycle in place of the 3-day cycle in OceanMAPSv4p0i. OceanMAPSv4p1i utilises an asynchronous data assimilation of observations, including Sea Surface Temperature (SST; 2-hourly), SLA (12-hourly), and temperature and salinity profiles (daily). OceanMAPSv4p1i produces better performance in forecast skill and mean absolute error scores in Sea Level Anomaly, Sea Surface Temperature and subsurface Temperature. Improvements gained are greater in surface fields, such as sea level anomaly and sea surface temperature, which have less persistence and a greater tendency. A reduction of ~10 % in SST errors and a ~7–8 % reduction in SLA errors is demonstrated in forecast stats. OceanMAPSv4p1i forecasts also better represent mesoscale ocean eddies.