27 Jul 2023
 | 27 Jul 2023

Analytical and adaptable initial conditions for moist baroclinic waves in a global hydrostatic model

Clément Bouvier, Daan van den Broek, Madeleine Ekblom, and Victoria A. Sinclair

Abstract. This article presents a description of an analytical, stable and flexible initial background state for moist baroclinic wave simulation on an aquaplanet in order to test dynamical core of numerical weather prediction models and study the dynamics and evolution of extra-tropical cyclones. The initial background state is derived from an analytical zonal wind speed field, or jet structure, and the hydrostatic primitive equations for moist adiabatic and frictionless flow in spherical coordinates. A baroclinic wave can develop only if a unbalanced perturbation is added to the zonal wind speed field. The implementation of this baroclinic wave simulation have been done on the Open Integrated Forecasting System (OpenIFS) cy43r3, a global numerical weather prediction model developed by the European Centre for Medium-range Weather Forecasts. In total, seven parameters can be used to control the generation of the initial background state and hence the development of the baroclinic waves in the OpenIFS configuration file: the jet's width, the jet's height, the maximum zonal mean wind speed of the jet, the horizontal mean of the surface virtual temperature, the surface relative humidity, the lapse rate and the surface roughness. Nine dry and nine moist initial background states have been generated to test their stability without perturbations. The meteorological stability of the initial state is investigated by examining the spatial distributions of the equivalent potential temperature, the absolute vorticity and the Brunt-Väisälä frequency. Moreover, the Root-Mean-Squared-Error (RMSE) of the zonal wind speed has been computed to assess their numerical stability. Finally, six of these moist initial initial background state have been used with an unbalanced perturbation to ensure that the baroclinic lifecycles developing are physically realistic. The resulting baroclinic wave is shown to be sensitive to the jet's width. This configuration for baroclinic wave simulations will be used to create large baroclinic lifecycles ensemble to study how extra-tropical cyclones may evolve in the future.

Clément Bouvier, Daan van den Broek, Madeleine Ekblom, and Victoria A. Sinclair

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on egusphere-2023-1078', Astrid Kerkweg, 18 Aug 2023
    • AC1: 'Reply on CEC1', Clément Bouvier, 11 Sep 2023
    • AC3: 'Reply on CEC1', Clément Bouvier, 31 Jan 2024
  • RC1: 'Comment on egusphere-2023-1078', Anonymous Referee #1, 12 Sep 2023
  • RC2: 'Comment on egusphere-2023-1078', Anonymous Referee #2, 07 Nov 2023
Clément Bouvier, Daan van den Broek, Madeleine Ekblom, and Victoria A. Sinclair
Clément Bouvier, Daan van den Broek, Madeleine Ekblom, and Victoria A. Sinclair


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Short summary
An analytical initial background state has been developed for moist baroclinic wave simulation on an aquaplanet and implemented into OpenIFS. Seven parameters can be controlled, which are used to generate the background states and the development of baroclinic waves. The meteorological and numerical stability have been assessed. Resulting baroclinic waves have been proven to be realistic and sensitive to the jet's width.