Preprints
https://doi.org/10.5194/wcd-2021-56
https://doi.org/10.5194/wcd-2021-56

  26 Aug 2021

26 Aug 2021

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

Atmospheric Blocking and Weather Extremes over the Euro-Atlantic Sector – A Review

Lisa-Ann Kautz1, Olivia Martius2, Stephan Pfahl3, Joaquim G. Pinto1, Alexandre M. Ramos4, Pedro M. Sousa4,5, and Tim Woollings6 Lisa-Ann Kautz et al.
  • 1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 2Institute of Geography, and Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 3Institute of Meteorology, Freie Universität Berlin, Berlin, Germany
  • 4Instituto Dom Luiz (IDL), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
  • 5Instituto Português do Mar e da Atmosfera (IPMA), 1749-077 Lisboa, Portugal
  • 6Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK

Abstract. The physical understanding and timely prediction of extreme weather events are of enormous importance to society regarding associated impacts. In this article, we highlight several types of weather extremes occurring in Europe in connection with a particular atmospheric flow pattern, known as atmospheric blocking. This flow pattern effectively blocks the prevailing westerly large-scale atmospheric flow, resulting in changing flow anomalies in the vicinity of the blocking system and persistent conditions in the immediate region of its occurrence. Blockings are long-lasting, quasi-stationary, self-sustaining systems that occur frequently over certain regions. Their presence and characteristics have an impact on the predictability of weather extremes and can thus be used as potential indicators. The phasing between the surface and the upper-level blocking anomalies is of major importance for the development of the extreme event. In summer, heat waves and droughts form below the blocking anticyclone primarily via large-scale subsidence that leads to cloud-free skies and thus, persistent longwave radiative warming of the ground. In winter, cold waves that occur during atmospheric blocking are normally observed downstream or south of these systems. Here, horizontal advection of cold air masses from higher latitudes plays a decisive role. Extreme snowfall can also occur with the lower temperatures, indicating a shift of the storm track due to the blocking system. Such a shift is also crucial in the connection of blocking with wind and precipitation anomalies in general. Due to this multifaceted linkages, compound events are often observed in conjunction with blocking conditions.

Lisa-Ann Kautz et al.

Status: open (until 07 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2021-56', Anonymous Referee #1, 08 Sep 2021 reply

Lisa-Ann Kautz et al.

Lisa-Ann Kautz et al.

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Short summary
Atmospheric blocking is associated with stationary, self-sustaining, long-living high pressure systems. They can cause or at least influence surface weather extremes, such as heat waves, cold spells, heavy precipitation events, droughts, or wind extremes. The location of the blocking determines where and what type of extreme event will occur. These relationships are also important for weather prediction and may change due to global warming.