Assessing the Impact of Ocean In Situ Observations on MJO Propagation Across the Maritime Continent in ECMWF Subseasonal Forecasts Journal of Advances in Modeling Earth Systems

Despite the well-recognized initial value nature of the subseasonal forecasts, the role of subsurface ocean initialization in subseasonal forecasts remains underexplored. Using observing system experiments, this study investigates the impact of ocean in situ data assimilation on the propagation of Madden– Julian Oscillation (MJO) events across the Maritime Continent in the European Centre for Medium-Range Weather Forecasts (ECMWF) subseasonal forecast system. Two sets of twin experiments are analyzed, which only differ on the use or not of in situ ocean observations in the initial conditions. Besides using the Real-time Multivariate MJO Index (RMMI) to evaluate the forecast performance, we also develop a new MJO tracking