A high-resolution atmosphere-ocean coupled model for the western Maritime Continent: development and preliminary assessment

Abstract

The article describes the configuration and preliminary assessment of a high-resolution atmosphere–ocean coupled model developed for the western Maritime Continent (MC). Regional configurations of the UK Met Office Unified Model (MetUM) and the Nucleus for European Modelling of the Ocean (NEMO) model are used as the atmosphere and ocean components of the coupled system. The OASIS3-MCT libraries have been employed for the exchange of heat, fresh water and momentum fluxes between these two components. Both models have a same horizontal resolution of 4.5 km × 4.5 km and similar domain. The atmospheric and ocean initial condition to the coupled model is derived from ERA-interim reanalysis and ocean-only model hindcast simulation, respectively. First, we compare the ocean-only surface as well as subsurface temperature and salinity simulations with observations/reanalysis. Then to assess the performance of the coupled model, 5-day forecast of a cold surge event on 23–27 January 2016 and typhoon Sarika on 16–20 October 2016 are performed. Further, to investigate the impact of air–sea coupling, the model simulations are compared with the atmosphere-only and ocean-only model simulations. The coupled forecast shows improvement in the simulation of low level winds, surface air temperature, sea surface height and sea surface temperature during the cold surge. Though the influence of coupling on the typhoon track prediction is mixed, the coupled model performs better in terms of the intensity, structure and dissipation of the typhoon. Overall, the coupling has improved the model skill in predicting the atmosphere/ocean variables, and the impact of coupling on atmospheric parameters is particularly noticeable over the oceanic region.