A Cartesian, small- to mesoscale nonhydrostatic model is extended to a rota
ting mountainous sphere, thereby dispensing with the traditional geophysica
l simplifications of hydrostaticity, gentle terrain slopes, and weak rotati
on. The authors discuss the algorithmic design, relative efficiency, and ac
curacy of several different variants (hydrostatic, nonhydrostatic, implicit
, explicit, elastic, anelastic, etc.) of the global model and prepare the g
round for a future "global cloud model''- a research tool to study effects
of small- and mesoscale phenomena on global flows and vice versa. There are
two primary threads to the discussion: (a) presenting a novel semi-implici
t anelastic global dynamics model as it naturally emerges from a small- sca
le dynamics model, and (b) demonstrating that nonhydrostatic anelastic glob
al models derived from small- scale codes adequately capture a broad range
of planetary flows while requiring relatively minor overhead due to the non
hydrostatic formulation of the governing equations. The authors substantiat
e their theoretical discussions with a detailed analysis of numerous simula
tions of idealized global orographic flows and climate states.