Preprints
https://doi.org/10.5194/wcd-2021-30
https://doi.org/10.5194/wcd-2021-30

  07 Jun 2021

07 Jun 2021

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

The role of tropopause polar vortices in the intensification of summer Arctic cyclones

Suzanne Louise Gray1, Kevin Ivan Hodges1,2, Jonathan Luke Vautrey1,a, and John Methven1 Suzanne Louise Gray et al.
  • 1Department of Meteorology, University of Reading, Reading, RG6 6ET, UK
  • 2National Centre for Atmospheric Science, University of Reading, Reading, RG6 6ET, UK
  • anow at: Met Office, Exeter, UK

Abstract. Human activity in the Arctic is increasing as new regions become accessible, with a consequent need for improved understanding of hazardous weather there. Arctic cyclones are the major weather systems affecting the Arctic environment during summer, including the sea ice distribution. Meso- to synoptic-scale tropopause polar vortices (TPVs) frequently occur in polar regions and are a proposed mechanism for Arctic cyclone genesis and intensification. However, while the importance of pre-existing tropopause-level features for cyclone development, and their existence as part of the three-dimensional mature cyclone structure, is well established in the mid-latitudes, evidence of the importance of pre-existing TPVs for Arctic cyclone development is mainly limited to a few case studies. Here we examine the extent to which Arctic cyclone growth is coupled to TPVs by analysing a climatology of summer Arctic cyclones and TPV characteristics produced by tracking both features in the latest ECMWF reanalysis (ERA5).

The annual counts of Arctic cyclones and TPVs are significantly correlated for features with genesis either within or outside the Arctic, implying that TPVs have a role in the development of Arctic cyclones. However, from their proximity, only about one third of Arctic cyclones intensify while influenced by a TPV and a maximum of 10 % have a nearby TPV at their genesis time. Consistent with the track densities of the full sets of Arctic cyclones and TPVs, cyclones associated with TPVs during their intensification phase (matched cyclones) track preferentially over the Arctic Ocean along the North American coastline and Canadian Archipelago. In contrast, cyclones intensifying distant from any TPV (unmatched cyclones) track preferentially along the north coast of Eurasia. Composite analysis reveals the presence of a distinct relative vorticity maximum at and above the tropopause level associated with the TPV throughout the intensification period for matched cyclones and that these cyclones have a reduced upstream tilt compared to unmatched cyclones. Interaction of cyclones with TPVs has implications for the predictability of Arctic weather, given the long lifetime, but relatively small spatial scale of TPVs compared with the density of the polar observation network.

Suzanne Louise Gray et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2021-30', Anonymous Referee #1, 13 Jun 2021
  • RC2: 'Comment on wcd-2021-30', Anonymous Referee #2, 06 Jul 2021
  • RC3: 'Comment on wcd-2021-30', Anonymous Referee #3, 07 Jul 2021
  • AC1: 'Response to reviewers', Suzanne L. Gray, 12 Aug 2021

Suzanne Louise Gray et al.

Suzanne Louise Gray et al.

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Short summary
This research demonstrates, using feature identification and tracking, that anticlockwise rotating vortices at about 7 km altitude called tropopause polar vortices frequently interact with storms developing in the Arctic region, affecting their structure and where they occur. This interaction has implications for the predictability of Arctic weather, given the long lifetime, but relatively small spatial scale of these vortices compared with the density of the polar observation network.