Simulation of Upper-Level Frontogenesis with a 20-Level Isentropic Coordinate Primitive Equation Model

Abstract

A numerical simulation using the inviscid adiabatic primitive equations for atmospheric motion framed in isentropic coordinates is shown to generate upper-level frontogenesis with physical and dynamical similarity to that shown in real upper-level frontal zones. Calculations of vertical velocity and potential vorticity show evidence of descent of stratospheric air into the upper portion of the simulated frontal zone. An experiment in which six isentropic surfaces intersect the earth's surface produces no numerical instabilities at the intersection, even in the presence of warm frontogenesis. Results suggest the suitability of the isentropic coordinate frame for numerical prediction of real weather systems containing frontal zone-jet stream systems.