Implementation of an ocean mixed layer model in IFS

TitleImplementation of an ocean mixed layer model in IFS
Publication TypeMiscellaneous
Year of Publication2010
AuthorsTakaya, Y, Vitart, F, Balsamo, G, M. Balmaseda, A, Leutbecher, M, Molteni, F
Secondary TitleTechnical Memorandum
Number622
Abstract

An ocean mixed layer model has been implemented in the ECMWF Integrated Forecasting System (IFS) in order to have a better representation of the atmosphere-upper ocean coupled processes in the ECMWF medium-range forecasts. The ocean mixed layer model uses a non-local K profile parameterization (KPP; Large et al. 1994). This model is a one-dimensional column model with high vertical resolution near the surface to simulate the diurnal thermal variations in the upper ocean. Its simplified dynamics makes it cheaper than a full ocean general circulation model and its implementation in IFS allows the atmosphere-ocean coupled model to run much more efficiently than using a coupler. The atmosphere-ocean mixed layer coupled model has been assessed by computing the skill of ensemble 10-day and monthly forecasts. Preliminary verifications indicate that the overall skill scores of the ensemble forecast are comparable to the skill scores of the current operational system. However, the ocean mixed-layer model has a positive impact on the prediction of the Madden Julian Oscillation and the Indian monsoon. The ocean mixed-layer model has also an impact on the intensity of tropical cyclones. The diurnal variability of SST which is important for future applications such as data assimilation with coupled models has also been evaluated.