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
Related authors
Henrik Auestad, Clemens Spensberger, Andrea Marcheggiani, Paulo Ceppi, Thomas Spengler, and Tim Woollings
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.
Andrea Marcheggiani and Thomas Spengler
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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There is a gap between the theoretical understanding and model representation of moist diabatic effects on the evolution of storm tracks. We seek to bridge this gap by exploring the relationship between diabatic and adiabatic contributions to changes in baroclinicity. We find reversed behaviours in the lower and upper troposphere in the maintenance of baroclinicity. In particular, our study reveals a link between higher moisture availability and upper-tropospheric restoration of baroclinicity.
Svenya Chripko, Thomas Spengler, Stefanie Semper, and Kjetil Våge
EGUsphere, https://doi.org/10.5194/egusphere-2025-4944, https://doi.org/10.5194/egusphere-2025-4944, 2025
This preprint is open for discussion and under review for Ocean Science (OS).
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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.
Clemens Spensberger, Kjersti Konstali, and Thomas Spengler
Weather Clim. Dynam., 6, 431–446, https://doi.org/10.5194/wcd-6-431-2025, https://doi.org/10.5194/wcd-6-431-2025, 2025
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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.
Chris Weijenborg and Thomas Spengler
EGUsphere, https://doi.org/10.5194/egusphere-2024-3404, https://doi.org/10.5194/egusphere-2024-3404, 2024
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The swift succession of storms, referred to as cyclone clustering, is often associated with weather extremes. We introduce a detection scheme for these events and subdivide these into two types. One type is associated with storms that follow each other in space, whereas the other type requires a proximity over time. Cyclone clustering is more frequent during winter and the first type is associated with stronger storms, suggesting that the two types emerge due to different mechanisms.
Henrik Auestad, Clemens Spensberger, Andrea Marcheggiani, Paulo Ceppi, Thomas Spengler, and Tim Woollings
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
Short summary
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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.
Fumiaki Ogawa and Thomas Spengler
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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The exchange of energy and moisture between the atmosphere and ocean is maximised along strong meridional contrasts in sea surface temperature, such as across the Gulf Stream and Kuroshio. We find that these strong meridional contrasts confine and determine the position of evaporation and precipitation, as well as storm occurrence and intensity. The general intensity of the water cycle and storm activity, however, is determined by the underlying absolute sea surface temperature.
Christiane Duscha, Juraj Pálenik, Thomas Spengler, and Joachim Reuder
Atmos. Meas. Tech., 16, 5103–5123, https://doi.org/10.5194/amt-16-5103-2023, https://doi.org/10.5194/amt-16-5103-2023, 2023
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We combine observations from two scanning Doppler lidars to obtain new and unique insights into the dynamic processes inherent to atmospheric convection. The approach complements and enhances conventional methods to probe convection and has the potential to substantially deepen our understanding of this complex process, which is crucial to improving our weather and climate models.
Andrea Marcheggiani and Thomas Spengler
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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There is a gap between the theoretical understanding and model representation of moist diabatic effects on the evolution of storm tracks. We seek to bridge this gap by exploring the relationship between diabatic and adiabatic contributions to changes in baroclinicity. We find reversed behaviours in the lower and upper troposphere in the maintenance of baroclinicity. In particular, our study reveals a link between higher moisture availability and upper-tropospheric restoration of baroclinicity.
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
Weather Clim. Dynam., 4, 95–114, https://doi.org/10.5194/wcd-4-95-2023, https://doi.org/10.5194/wcd-4-95-2023, 2023
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Strong disagreement exists in the scientific community over the role of Arctic sea ice in shaping wintertime Eurasian cooling. The observed Eurasian cooling can arise naturally without sea-ice loss but is expected to be a rare event. We propose a framework that incorporates sea-ice retreat and natural variability as contributing factors. A helpful analogy is of a dice roll that may result in cooling, warming, or anything in between, with sea-ice loss acting to load the dice in favour of cooling.
Tim Woollings, Camille Li, Marie Drouard, Etienne Dunn-Sigouin, Karim A. Elmestekawy, Momme Hell, Brian Hoskins, Cheikh Mbengue, Matthew Patterson, and Thomas Spengler
Weather Clim. Dynam., 4, 61–80, https://doi.org/10.5194/wcd-4-61-2023, https://doi.org/10.5194/wcd-4-61-2023, 2023
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This paper investigates large-scale atmospheric variability in polar regions, specifically the balance between large-scale turbulence and Rossby wave activity. The polar regions are relatively more dominated by turbulence than lower latitudes, but Rossby waves are found to play a role and can even be triggered from high latitudes under certain conditions. Features such as cyclone lifetimes, high-latitude blocks, and annular modes are discussed from this perspective.
Clemens Spensberger, Trond Thorsteinsson, and Thomas Spengler
Geosci. Model Dev., 15, 2711–2729, https://doi.org/10.5194/gmd-15-2711-2022, https://doi.org/10.5194/gmd-15-2711-2022, 2022
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In order to understand the atmosphere, we rely on a hierarchy of models ranging from very simple to very complex. Comparing different steps in this hierarchy usually entails comparing different models. Here we combine two such steps that are commonly used in one modelling framework. This makes comparisons both much easier and much more direct.
Leonidas Tsopouridis, Thomas Spengler, and Clemens Spensberger
Weather Clim. Dynam., 2, 953–970, https://doi.org/10.5194/wcd-2-953-2021, https://doi.org/10.5194/wcd-2-953-2021, 2021
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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.
Kristine Flacké Haualand and Thomas Spengler
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.
Patrick Johannes Stoll, Thomas Spengler, Annick Terpstra, and Rune Grand Graversen
Weather Clim. Dynam., 2, 19–36, https://doi.org/10.5194/wcd-2-19-2021, https://doi.org/10.5194/wcd-2-19-2021, 2021
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Polar lows are intense meso-scale cyclones occurring at high latitudes. The research community has not agreed on a conceptual model to describe polar-low development. Here, we apply self-organising maps to identify the typical ambient sub-synoptic environments of polar lows and find that they can be described as moist-baroclinic cyclones that develop in four different environments characterised by the vertical wind shear.
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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...
