Medium-range forecasting with a hybrid-isentropic global circulation model

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Thursday, 6 February 2014
Hall C3 (The Georgia World Congress Center )
Rainer Bleck, NASA Goddard Institute for Space Studies & NOAA/Earth System Research Laboratory, Boulder, CO; and J. W. Bao, S. Benjamin, M. Fiorino, G. Grell, T. Henderson, B. Jamison, J. Lee, P. Madden, J. Middlecoff, J. Rosinski, T. Smirnova, S. Sun, and N. Wang

Handout (5.0 MB)

Attempts to simulate atmospheric motion with a numerical model using potential temperature as vertical coordinate date back to the mid-1960s, with D.Johnson, J.Dutton and A.Eliassen being the main protagonists. One of the latest contributions to this line of work is a global model employing a "hybrid" vertical coordinate that is terrain-following near the surface but quickly transitions to potential temperature aloft. The model, developed at NOAA-ESRL, is hydrostatic and uses an icosahedral horizontal mesh to achieve near-uniform global grid resolution. Daily real-time forecasts at 15-30km grid resolution, based on initial fields supplied by NCEP-GFS, are presently being evaluated and compared to operational forecasts by a number of weather centrals.

Having proven its ability to deliver competitive medium-range forecasts, the model (called FIM -- see http://fim.noaa.gov) is presently being tested for possible use in intraseasonal to interannual prediction work. The interactive ocean model needed on these time scales also uses an icosahedral grid (to simplify coupling) and a vertical grid analogous to the hybrid FIM grid. As such, the ocean model is yet another manifestation of the "isentropic viewpoint" championed by Johnson.