Abstract. We have used a normal-mode analysis to investigate the impacts
of the horizontal and vertical discretizations on the numerical solutions of
the nonhydrostatic anelastic inertia–gravity modes on a midlatitude
f plane. The dispersion equations are derived from the linearized anelastic
equations that are discretized on the Z, C, D, CD, (DC), A, E and B
horizontal grids, and on the L and CP vertical grids. The effects of both
horizontal grid spacing and vertical wavenumber are analyzed, and the role
of nonhydrostatic effects is discussed. We also compare the results of the
normal-mode analyses with numerical solutions obtained by running linearized
numerical models based on the various horizontal grids. The sources and
behaviors of the computational modes in the numerical simulations are also
examined. Our normal-mode analyses with the Z, C, D, A, E and B grids generally confirm
the conclusions of previous shallow-water studies for the cyclone-resolving
scales (with low horizontal wavenumbers). We conclude that, aided by
nonhydrostatic effects, the Z and C grids become overall more accurate for
cloud-resolving resolutions (with high horizontal wavenumbers) than for the
cyclone-resolving scales. A companion paper, Part 2, discusses the impacts of the discretization on the
Rossby modes on a midlatitude β plane.