Towards a high-resolution global coupled navy prediction system

A fully coupled global atmosphere-ocean prediction system for short-term forecasting has been developed at NRL Monterey at modestly high horizontal resolution (0.5/spl deg/ ocean and 0.75/spl deg/ atmosphere). University and national laboratory partners are performing coupled ice/ocean simulations, improving the data assimilation scheme, and running high-resolution ocean simulations with the goal of advancing this prediction system. Sea ice in the 0.4/spl deg/ global coupled ocean/ice system in the Arctic is seen to respond to synoptic wind events on time scales of a day, producing thickening and thinning of the ice. The data assimilation scheme, SODA (Simple Ocean Data Assimilation Scheme), when used together with eddy-permitting POP produces variability in the Gulf Stream that is comparable with that from altimetry both in terms of magnitude and distribution. The high resolution global POP (Parallel Ocean Program) forced with NOGAPS surface fluxes produces slightly more realistic variability in the tropical Indian and Pacific Oceans relative to the NCEP-forced simulation. Outside of the tropics, the variability produced by the two simulations is in close agreement; generally both simulations agree with data. The inclusion of ice in the coupled system will produce a more realistic thermohaline circulation in the ocean as well as providing a more realistic time-dependent bottom boundary layer to NOGAPS (Naval Operational Global Atmospheric System). The improved data assimilation scheme will produce more realistic analyses, while the use of high-resolution will improve the model forecast by reducing biases resulting from lack of sufficient resolution.