Robust identification of impactful boreal summer anticyclones
- 1Corresponding author.
- 2Department of Physics, University of Toronto, Toronto, Ontario, Canada
Abstract
Impactful midlatitude heatwaves are often triggered by persistent anticyclonic atmospheric blocks. Objectively defining such impactful blocking circulations remains a challenge for climate impacts analysis and theoretical understanding, which this work seeks to address. Here, persistent midtropospheric anticyclones over the entire northern hemisphere midlatitude region that lead to anomalously warm surface conditions are identified, independently of specific blocking metrics, with a two-step identification method. This method's input is daily boreal-summer midtropospheric geopotential height, from reanalysis or from earth-system models (ESMs), over a circumglobal set of midlatitude domains spanning about 60 ∘ longitude and 40 ∘ latitude. The method's output is a set of days featuring persistent states that reflect the predominant flow pattern, Archetype 1 , extracted using archetype analysis. Persistence is defined by high values of a persistence metric , symbolized θ − 1 , that reflects how long the atmosphere tends to stay near a specific atmospheric configuration. The high- θ − 1 Archetype 1 is a barotropic anticyclonic block with warm surface conditions, lasting about a week. Extending previous European-domain persistence analysis, the archetype analysis filters out less-impactful persistent cyclonic systems associated with anomalously cold conditions. Over land regions, heatwaves are 5-10 times more frequent under persistent Archetype 1 conditions than in the record as a whole. Persistent Archetype 1 patterns are realistically represented in historical ESM simulations. Under anthropogenic global warming, their spatial structure is robust, but their persistence increases by about 7% and their surface warming intensifies by the end of the 21st century.
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BibTeX
@article{vakrat2026robust,
title = {{Robust identification of impactful boreal summer anticyclones}},
author = {Eylon Vakrat and Paul J. Kushner},
journal = {Weather and Climate Extremes},
year = {2026},
month = oct,
doi = {10.1016/j.wace.2026.100962},
url = {https://doi.org/10.1016/j.wace.2026.100962},
note = {CC BY},
}
RIS
TY - JOUR
TI - Robust identification of impactful boreal summer anticyclones
AU - Eylon Vakrat
AU - Paul J. Kushner
PY - 2026
DA - 2026/10/30
JO - Weather and Climate Extremes
DO - 10.1016/j.wace.2026.100962
UR - https://doi.org/10.1016/j.wace.2026.100962
AB - Impactful midlatitude heatwaves are often triggered by persistent anticyclonic atmospheric blocks. Objectively defining such impactful blocking circulations remains a challenge for climate impacts analysis and theoretical understanding, which this work seeks to address. Here, persistent midtropospheric anticyclones over the entire northern hemisphere midlatitude region that lead to anomalously warm surface conditions are identified, independently of specific blocking metrics, with a two-step identification method. This method's input is daily boreal-summer midtropospheric geopotential height, from reanalysis or from earth-system models (ESMs), over a circumglobal set of midlatitude domains spanning about 60 ∘ longitude and 40 ∘ latitude. The method's output is a set of days featuring persistent states that reflect the predominant flow pattern, Archetype 1 , extracted using archetype analysis. Persistence is defined by high values of a persistence metric , symbolized θ − 1 , that reflects how long the atmosphere tends to stay near a specific atmospheric configuration. The high- θ − 1 Archetype 1 is a barotropic anticyclonic block with warm surface conditions, lasting about a week. Extending previous European-domain persistence analysis, the archetype analysis filters out less-impactful persistent cyclonic systems associated with anomalously cold conditions. Over land regions, heatwaves are 5-10 times more frequent under persistent Archetype 1 conditions than in the record as a whole. Persistent Archetype 1 patterns are realistically represented in historical ESM simulations. Under anthropogenic global warming, their spatial structure is robust, but their persistence increases by about 7% and their surface warming intensifies by the end of the 21st century.
SN - 2212-0947
ER -