A new grid for the IFS
Malardel, Sylvie ; Wedi, Nils ; Deconinck, Willem ; Diamantakis, Michail ; Kühnlein, Christian ; Mozdzynski, George ; Hamrud, Mats ; Smolarkiewicz, Piotr
Année de publication
ECMWF will implement a resolution upgrade for high-resolution forecasts (HRES) and ensemble forecasts (ENS) in spring 2016. HRES will then be run on a grid with a grid-point distance between neighbouring points of approximately 9 km instead of 16 km in the current configuration. In the Integrated Forecasting System (IFS), many calculations are not carried out in grid-point space but in ‘spectral space’, where meteorological fields are represented by a sum of wave functions called spherical harmonics. As part of the resolution upgrade, ECMWF will move from a ‘linear’ to a ‘cubic’ grid by increasing the number of grid points used to represent each wavelength while keeping the number of spherical harmonics constant. At the same time, it will use an octahedron-based method to reduce the number of grid points towards the poles. The resulting new ‘cubic-octahedral’ grid brings significant benefits in terms of computational efficiency and effective resolution.