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Progress toward a NOAA-ESRL earth system model: coupling an atmosphere to an ocean
Shan Sun, Rainer Bleck
NOAA/ESRL
(Abstract received 12/27/2010 for session X)
ABSTRACT
A long-range global weather prediction model developed at ESRL is currently being coupled to a HYCOM-type ocean. The atmospheric model (http://fim.noaa.gov) uses an icosahedral horizontal grid and a hybrid-isentropic vertical coordinate, also reminiscent of HYCOM. Grid nesting is common in weather modeling, but grid discontinuities are usually kept away from the region of interest. To avoid joining disparate grids at the ocean-atmosphere interface (arguably the region of interest in coupled modeling), HYCOM is currently being re-coded for an icosahedral grid. With FIM being run operationally at mesh sizes of 15km and 30km, an ocean component sharing the FIM grid will therefore be eddy-permitting. Interseasonal forecasts at that resolution may not be feasible in near future, however. The mathematical similarity of the two models (same number of variables and equations, same vertical coordinate) allows them to share the dynamic core and software engineering innovations developed for FIM. A numerical problem in the barotropic-baroclinic mode splitting scheme, originally developed for HYCOM, forces us to run the icosahedral HYCOM in unsplit mode for the time being. Preliminary results from the coupled model will be discussed.
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2011 LOM Workshop, Miami, Florida February 7 - 9, 2011