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A proposed baroclinic wave test case for deep- and shallow-atmosphere dynamical cores
Version of Record online: 2 DEC 2013
© 2013 Royal Meteorological Society and Crown Copyright, the Met Office. Quarterly Journal of the Royal Meteorological Society © 2013 Royal Meteorological Society
Quarterly Journal of the Royal Meteorological Society
Volume 140, Issue 682, pages 1590–1602, July 2014 Part A
How to Cite
Ullrich, P. A., Melvin, T., Jablonowski, C. and Staniforth, A. (2014), A proposed baroclinic wave test case for deep- and shallow-atmosphere dynamical cores. Q.J.R. Meteorol. Soc., 140: 1590–1602. doi: 10.1002/qj.2241
- Issue online: 28 JUL 2014
- Version of Record online: 2 DEC 2013
- Accepted manuscript online: 29 AUG 2013 12:58PM EST
- Manuscript Accepted: 25 AUG 2013
- Manuscript Revised: 20 AUG 2013
- Manuscript Received: 26 NOV 2012
- baroclinic instability;
- model intercomparison;
- small Earth
Idealised studies of key dynamical features of the atmosphere provide insight into the behaviour of atmospheric models. A very important, well understood, aspect of midlatitude dynamics is baroclinic instability. This can be idealised by perturbing a vertically sheared basic state in geostrophic and hydrostatic balance. An unstable wave mode then results with exponential growth (due to linear dynamics) in time until, eventually, nonlinear effects dominate and the wave breaks.
A new, unified, idealised baroclinic instability test case is proposed. This improves on previous ones in three ways. First, it is suitable for both deep- and shallow-atmosphere models. Second, the constant surface pressure and zero surface geopotential of the basic state makes it particularly well-suited for models employing a pressure- or height-based vertical coordinate. Third, the wave triggering mechanism selectively perturbs the rotational component of the flow; this, together with a vertical tapering, significantly improves dynamic balance.