Parallelizing the ECMWF'S weather forecast program: The 2D case

GMD and ECMWF (European Centre for Medium-Range Weather Forecasts) joined forces some months ago in order to parallelize ECMWF's production code for medium-range weather forecasts, the Integrated Forecasting System (IFS). Meanwhile, the first milestone of this cooperation has been reached: The 2D model of the IFS, which contains already all relevant data structures and algorithmic components of the corresponding 3D models, has been parallelized and run successfully on quite a large variety of differential parallel machines. Performance measurements confirm the expected parallel efficiencies of up to 80% and more. This paper discusses the parallelization strategy employed and gives a survey on the performance results obtained on the parallel systems