A simplified model of the Martian atmosphere -- Part 1: a diagnostic analysis

In this paper we derive a reduced-order approximation to the vertical and horizontal structure of a simplified model of the baroclinically unstable Martian atmosphere. The original model uses the full hydrostatic primitive equations on a sphere, but has only highly simplified schemes to represent the detailed physics of the Martian atmosphere, e.g. forcing towards a plausible zonal mean temperature state using Newtonian cooling. Three different norms are used to monitor energy conversion processes in the model and are then compared. When four vertical modes (the barotropic and first three baroclinic modes) are retained in the reducedorder approximation, the correlation norm captures approximately 90% of the variance, while the kinetic energy and total energy norms capture approximately 83% and 78% of the kinetic and total energy respectively. We show that the leading order Proper Orthogonal Decomposition (POD) modes represent the dominant travelling waves in the baroclinicallyunstable, winter hemisphere. In part 2 of our study we will develop a hierarchy of truncated POD-Galerkin expansions of the model equations using up to four vertical modes.Citation: Whitehouse, S. G. et al. (2005). 'A simplified model of the Martian atmosphere - Part 1: a diagnostic analysis', Nonlinear Processes in Geophysics, 12(5), 603-623. [Available at http://www.nonlin-processes-geophys.net/12/603/2005/]. © Authors 2005. This article is distributed under the terms of the Creative Commons Attribution, NonCommercial and ShareAlike License (http://creativecommons.org/licenses/by-nc-sa/2.0/deed.en). This permits the copying and distribution of the work, and the making of derivative works, provided the original authors are credited. However, you may not use this work for commercial purposes, and if you alter, transform, or build upon this work, you must distribute the resulting work under a license identical to this one. For any reuse or distribution, you must make clear to others the license terms of this work. These conditions may be waived if you get permission from the copyright holder and, in the case of commercial use during the first five years, you also get permission from Copernicus Publications and the European Geosciences Union