A two-time-level semi-Lagrangian global spectral model



A three-time-level semi-Lagrangian global spectral model was introduced operationally at the European Centre for Medium-Range Weather Forecasts in 1991. This paper first documents some later refinements to the three-time-level scheme, and then describes its conversion to a two-time-level scheme. Experimental results are presented to show that the two-time-level scheme maintains the accuracy of its three-time-level predecessor, while being considerably more computationally efficient.