A class of nonhydrostatic global models

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.