Preprints
https://doi.org/10.5194/egusphere-2024-2112
https://doi.org/10.5194/egusphere-2024-2112
16 Jul 2024
 | 16 Jul 2024

Synoptic perspective on the conversion and maintenance of local available potential energy in extratropical cyclones

Marc Federer, Lukas Papritz, Michael Sprenger, and Christian M. Grams

Abstract. Extratropical cyclones are the predominant weather system in the midlatitudes. They intensify through baroclinic instability, a process in which available potential energy (APE) is converted into kinetic energy (KE). While the planetary-scale conversion of APE to KE is well understood as a mechanism for maintaining the general atmospheric circulation against dissipation, the synoptic-scale perspective on this conversion is less explored. In this study, we analyze the three-dimensional distribution of APE and the physical processes that consume APE for an illustrative case study and a climatology of 285 intense North Atlantic extratropical cyclones in the winters 1979–2021 using the ERA5 reanalysis. We utilize a recently introduced local APE framework that allows APE to be quantified at the level of individual air parcels. The geographical APE distribution is shown to be controlled by the large-scale upper-level circulation. Cyclones draw energy from the upper-tropospheric polar APE reservoir along with the development of the associated upper-level trough. This upper-level APE is converted into KE by air descending along the trough's western flank and acts as the incipient cyclone's primary source of KE. Conversely, KE is converted back into APE during the ascent ahead of the trough, reflecting the deceleration of air parcels as they exit the cyclone region. The diabatic dissipation of APE due to surface sensible heat fluxes along the Gulf Stream front is small compared to the adiabatic conversion of APE to KE, since most of the APE is concentrated and consumed in the middle to upper troposphere and cannot be exposed to surface diabatic forcing. In conclusion, by employing a local APE framework, this study provides a detailed investigation of the synoptic dynamics linking extratropical cyclones and planetary-scale energetics.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Marc Federer, Lukas Papritz, Michael Sprenger, and Christian M. Grams

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2024-2112', Kevin Bowley, 15 Aug 2024
  • RC1: 'Comment on egusphere-2024-2112', Kevin A. Bowley, 16 Aug 2024
  • RC2: 'Comment on egusphere-2024-2112', Lance F. Bosart, 25 Aug 2024
  • AC1: 'Final author comments on egusphere-2024-2112', Marc Federer, 02 Oct 2024
Marc Federer, Lukas Papritz, Michael Sprenger, and Christian M. Grams
Marc Federer, Lukas Papritz, Michael Sprenger, and Christian M. Grams

Viewed

Total article views: 438 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
282 88 68 438 7 9
  • HTML: 282
  • PDF: 88
  • XML: 68
  • Total: 438
  • BibTeX: 7
  • EndNote: 9
Views and downloads (calculated since 16 Jul 2024)
Cumulative views and downloads (calculated since 16 Jul 2024)

Viewed (geographical distribution)

Total article views: 462 (including HTML, PDF, and XML) Thereof 462 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 16 Nov 2024
Download
Short summary
Although extratropical cyclones in the North Atlantic are among the most impactful midlatitude weather systems, the potential for their growth on synoptic scales is not well understood. Here we show how they convert potential into kinetic energy through the descent of cold upper-tropospheric air from high latitudes. Surface processes, such as ocean heat exchange, have a smaller effect. Understanding these dynamics helps to explain the processes that maintain storm tracks.