Development and initial test of the University of Wisconsin global isentropic-sigma model

Abstract

The description of a global version of the University of Wisconsin (UW) hybrid isentropic-sigma (θ-σ) model and the results from an initial numerical weather prediction experiment are presented in this paper. Root-mean-square errors demonstrate that the θ-σ model is slightly more accurate than the nominally identical σ model with respect to standard synoptic variables. Of particular importance, the UW θ-σ model displays a distinct advantage over the conventional σ model with respect to prognostic simulation of inert trace constituent transport in amplifying baroclinic waves of the extratropics. This is especially true in the upper troposphere and stratosphere where the spatial integrity and conservation of an inert trace constituent is severely compromised in the σ model compared to the θ-σ model. -from Authors