DESIGN OF A THREE-DIMENSIONAL GLOBAL ADIABATIC SPECTRAL PRIMITIVE EQUATION MODEL*

A three-dimensional(3D) global adiabatic spectral primitive equation model has been designed.The main features are as follows.(1) Adoption of spherical harmonics and Tschebyscheff polynomials as the basis functions in the horizontal and vertical respectively,but the unknowns in the spectral equations are two-dimensional;(2) Inclusion of the tropopause,which may vary with time and space;(3) Suggestion of a spectral method for representing the vertical structure of the atmosphere applicable to the unsmoothed profile case;(4) In consideration of nonlinear vertical aliasing a technique is proposed to avoid it and nonlinear computational instability.Based on real data forecasts up to 48 hours have been performed.The results show that the statistical verifications with the model are superior on the average to those with the T42L9 used operationally before 1995 at NMC of China at the same mean resolution.