Preprints
https://doi.org/10.5194/wcd-2021-59
https://doi.org/10.5194/wcd-2021-59

  21 Sep 2021

21 Sep 2021

Review status: this preprint is currently under review for the journal WCD.

Circumglobal Rossby wave patterns during boreal winter highlighted by wavenumber/phase speed spectral analysis

Jacopo Riboldi1,3, Efi Rousi2, Fabio D'Andrea1, Gwendal Rivière1, and François Lott1 Jacopo Riboldi et al.
  • 1Laboratoire de Météorologie Dynamique, École Normale Supérieure, PSL University, Paris, France
  • 2Potsdam Institute for Climate Impact Research (PIK), Leibniz Association, Potsdam, Germany
  • 3Department of Earth Sciences, Uppsala University, Uppsala, Sweden

Abstract. The classic partitioning between slow-moving, low-wavenumber planetary waves and fast-moving, high-wavenumber synoptic waves is systematically extended by means of a wavenumber/phase speed spectral decomposition to characterize the day-to-day evolution of Rossby wave activity in the upper troposphere. This technique is employed to study the origin and the propagation of circumglobal Rossby wave patterns (CRWPs), amplified Rossby waves stretching across the Northern Hemisphere in the zonal direction and characterized by few, dominant wavenumbers. Principal component analysis of daily anomalies in spectral power allows for two CRWPs to emerge as dominant variability modes in the spectral domain during boreal winter. These modes correspond to the baroclinic propagation of amplified Rossby waves from the Pacific to the Atlantic storm track in a hemispheric flow configuration displaying enhanced meridional gradients of geopotential height over midlatitudes. The first CRWP is forced by tropical convection anomalies over the Indian Ocean and features the propagation of amplified Rossby wave packets over northern midlatitudes, while the second one propagates rapidly over latitudes between 35° N and 55° N and appears to have extratropical origin. Propagation of Rossby waves from the Atlantic eddy-driven jet to the African subtropical jet occurs for both CRWPs following anticyclonic wave breaking.

Jacopo Riboldi et al.

Status: open (until 02 Nov 2021)

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Jacopo Riboldi et al.

Jacopo Riboldi et al.

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Short summary
A revisited space/time spectral decomposition allows to determine which harmonics dominate the upper tropospheric flow evolution over a given time period as well as their propagation. This approach is used to identify Rossby wave patterns with a circumglobal extent, affecting weather evolution over different region of the Northern Hemisphere. The results cast light on the processes originating and supporting these wave patterns, advocating at the same time for the usefulness of the technique.