Articles | Volume 6, issue 4
https://doi.org/10.5194/wcd-6-1479-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wcd-6-1479-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
20 Nov 2025
Research article |
| 20 Nov 2025
| 20 Nov 2025
Cold air outbreaks drive near-surface baroclinicity variability over storm track entrance regions in the Northern Hemisphere
Andrea Marcheggiani
CORRESPONDING AUTHOR
Geophysical Institute, University of Bergen, and Bjerknes Centre for Climate Research, Bergen, Norway
Thomas Spengler
Geophysical Institute, University of Bergen, and Bjerknes Centre for Climate Research, Bergen, Norway
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This preprint is open for discussion and under review for Geoscientific Model Development (GMD).
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We propose an idealised framework to study how the shape of midlatitude SST fronts controls the atmospheric general circulation. The new SST profile enables separate changes in the geometric properties of extratropical SST fronts, such as strength, width, position, and maximum SST. The response of storm tracks, jets, and the water cycle to changes in frontal parameters are briefly discussed. This approach provides a basis for more targeted studies on the role of SST fronts on the atmosphere.
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Latent heating due to condensation can influence atmospheric circulation by strengthening or weakening horizontal temperature contrasts. Strong temperature contrasts intensify storms and imply the existence of strong upper tropospheric winds called jets. It remains unclear whether latent heating preferentially reinforces or abates the existing jet. We show that this disagreement is attributable to how the jet is defined, confirming that latent heating reinforces the jet.
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We propose an idealised framework to study how the shape of midlatitude SST fronts controls the atmospheric general circulation. The new SST profile enables separate changes in the geometric properties of extratropical SST fronts, such as strength, width, position, and maximum SST. The response of storm tracks, jets, and the water cycle to changes in frontal parameters are briefly discussed. This approach provides a basis for more targeted studies on the role of SST fronts on the atmosphere.
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Using a high-resolution ocean reanalysis, we provide the first quantification of the three-dimensional ocean response to a strong cold air outbreak in the entire Nordic Seas. We show that the effects of the cold air outbreak on the mixed layer are masked by the effects of lateral heat transport in the eastern part of the region. The effects are only visible in the western Nordic Seas (away from sea ice and currents), which impacts water mass transformation in the area.
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The transport of moisture from warmer and moister to colder and drier regions mainly occurs in brief and narrow bursts. In the mid-latitudes, such bursts are generally referred to as atmospheric rivers; in the Arctic they are often referred to as warm moist intrusions. We introduce a new definition to identify such bursts which is based primarily on their elongated structure. With this more general definition, we show that bursts in moisture transport occur frequently across all climate zones.
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Weather Clim. Dynam., 5, 1269–1286, https://doi.org/10.5194/wcd-5-1269-2024, https://doi.org/10.5194/wcd-5-1269-2024, 2024
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Latent heating due to condensation can influence atmospheric circulation by strengthening or weakening horizontal temperature contrasts. Strong temperature contrasts intensify storms and imply the existence of strong upper tropospheric winds called jets. It remains unclear whether latent heating preferentially reinforces or abates the existing jet. We show that this disagreement is attributable to how the jet is defined, confirming that latent heating reinforces the jet.
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Weather Clim. Dynam., 5, 1031–1042, https://doi.org/10.5194/wcd-5-1031-2024, https://doi.org/10.5194/wcd-5-1031-2024, 2024
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Weather Clim. Dynam., 4, 927–942, https://doi.org/10.5194/wcd-4-927-2023, https://doi.org/10.5194/wcd-4-927-2023, 2023
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Stephen Outten, Camille Li, Martin P. King, Lingling Suo, Peter Y. F. Siew, Hoffman Cheung, Richard Davy, Etienne Dunn-Sigouin, Tore Furevik, Shengping He, Erica Madonna, Stefan Sobolowski, Thomas Spengler, and Tim Woollings
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Comparing simulations with realistic and smoothed SSTs, we find that the intensification of individual cyclones in the Gulf Stream and Kuroshio regions is only marginally affected by reducing the SST gradient. In contrast, we observe a reduced cyclone activity and a shift in storm tracks. Considering differences of the variables occurring within/outside of a radius of any cyclone, we find cyclones to play only a secondary role in explaining the mean states differences among the SST experiments.
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Weather Clim. Dynam., 2, 695–712, https://doi.org/10.5194/wcd-2-695-2021, https://doi.org/10.5194/wcd-2-695-2021, 2021
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Given the recent focus on the influence of upper tropospheric structure in wind and temperature on midlatitude weather, we use an idealised model to investigate how structural modifications impact cyclone development. We find that cyclone intensification is less sensitive to these modifications than to changes in the amount of cloud condensation, suggesting that an accurate representation of the upper-level troposphere is less important for midlatitude weather than previously anticipated.
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Short summary
Cold air outbreaks, where cold polar air flows over warmer oceans, help restore midlatitude atmospheric temperature gradients near strong ocean currents, supporting storm formation. Using a novel method, we show that moderate outbreaks cover less than 15 % of the Gulf Stream region but explain up to 40 % of near-surface variability. In the North Pacific, they are more extensive and still account for a large share of variability, highlighting their key role in shaping storm tracks.
Cold air outbreaks, where cold polar air flows over warmer oceans, help restore midlatitude...
