A THREE-LEVEL FILTERED SPECTRAL MODEL FOR NORTHERN HEMISPHERE

A three-level filtered spectral forecast model including orography has been developed, using the difference method, vertically, the degradation of dimensionality, and a perfect spectral method latitudinally and pseudo-spectral methods longitudinally. The wave numbers taken along the parallels and the meridians are 15 and 13 respectively. In time integration, the time step is taken as a function of wave number. Since september in 1974,a number of examples have been computed, with fairly good results.