Articles | Volume 6, issue 4
https://doi.org/10.5194/wcd-6-1583-2025
© 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-6-1583-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| Highlight paper
| 
27 Nov 2025
Research article | Highlight paper |
| 27 Nov 2025
| 27 Nov 2025
Clear-air turbulence derived from in situ aircraft observation – a weather feature-based typology using ERA5 reanalysis
Ming Hon Franco Lee
CORRESPONDING AUTHOR
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Michael Sprenger
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
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Ambrogio Volonté, Hanna Joos, Ming Hon Franco Lee, Richard Forbes, and Rémi Bouffet-Klein
Weather Clim. Dynam., 7, 1241–1264, https://doi.org/10.5194/wcd-7-1241-2026, https://doi.org/10.5194/wcd-7-1241-2026, 2026
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Sting jets are air flows that can form in cloudy and unstable regions of intense windstorms. They can cause damaging wind gusts as they descend and accelerate while releasing their instability. We use a numerical simulation of Storm Ciarán to identify the individual cloud processes, such as condensation and sublimation, driving the onset of this instability. We reveal their complex interplay and highlight the unique properties of the three-dimensional environment in which a sting jet develops.
Ming Hon Franco Lee, Hanna Joos, Heini Wernli, Richard Forbes, and Michael Sprenger
EGUsphere, https://doi.org/10.5194/egusphere-2026-4184, https://doi.org/10.5194/egusphere-2026-4184, 2026
This preprint is open for discussion and under review for Weather and Climate Dynamics (WCD).
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Turbulence near jet streams modifies the atmospheric flow, but there is limited research on the underlying mechanism. In this study, we infer this feedback by tracing the change in potential vorticity. We use an analytical framework to explain the systematic changes caused by turbulence in a numerical simulation of a jet stream. A typical tripolar pattern appears repeatedly, and it is highly related to the coherence of the jet. The improved understanding may help advance weather forecasts.
Franziska Schnyder, Ming Hon Franco Lee, and Heini Wernli
Weather Clim. Dynam., 6, 1319–1337, https://doi.org/10.5194/wcd-6-1319-2025, https://doi.org/10.5194/wcd-6-1319-2025, 2025
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In this study, we investigate a particularly long-lived example of a Siberian summer cyclone, which originates during a heat wave in Kazakhstan in July 2021 and propagates into the Arctic, where it leads to heavy precipitation and alters the Arctic tropopause. Although a rare event in current climate, this case reveals how compounding events may be linked by one weather system and portrays a type of cyclone event which is likely to become more frequent in a warmer climate.
Matthias Röthlisberger, Michael Sprenger, Urs Beyerle, Erich M. Fischer, and Heini Wernli
Weather Clim. Dynam., 7, 1363–1384, https://doi.org/10.5194/wcd-7-1363-2026, https://doi.org/10.5194/wcd-7-1363-2026, 2026
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This study investigates yearly heat extremes simulated with the global climate model CESM2. A trajectory-based method is used, which allows quantifying the contributions to temperature anomalies from advection, subsidence, and diabatic heating. The results show that the magnitude of CESM2 heat extremes agrees fairly well with ERA5 reanalyses, but it is often
for the partly wrong physical reasons.
Ming Hon Franco Lee, Hanna Joos, Heini Wernli, Richard Forbes, and Michael Sprenger
EGUsphere, https://doi.org/10.5194/egusphere-2026-4184, https://doi.org/10.5194/egusphere-2026-4184, 2026
This preprint is open for discussion and under review for Weather and Climate Dynamics (WCD).
Short summary
Short summary
Turbulence near jet streams modifies the atmospheric flow, but there is limited research on the underlying mechanism. In this study, we infer this feedback by tracing the change in potential vorticity. We use an analytical framework to explain the systematic changes caused by turbulence in a numerical simulation of a jet stream. A typical tripolar pattern appears repeatedly, and it is highly related to the coherence of the jet. The improved understanding may help advance weather forecasts.
Ambrogio Volonté, Hanna Joos, Ming Hon Franco Lee, Richard Forbes, and Rémi Bouffet-Klein
Weather Clim. Dynam., 7, 1241–1264, https://doi.org/10.5194/wcd-7-1241-2026, https://doi.org/10.5194/wcd-7-1241-2026, 2026
Short summary
Short summary
Sting jets are air flows that can form in cloudy and unstable regions of intense windstorms. They can cause damaging wind gusts as they descend and accelerate while releasing their instability. We use a numerical simulation of Storm Ciarán to identify the individual cloud processes, such as condensation and sublimation, driving the onset of this instability. We reveal their complex interplay and highlight the unique properties of the three-dimensional environment in which a sting jet develops.
Ellina Agayar, Moshe Armon, Michael Sprenger, and Heini Wernli
Nat. Hazards Earth Syst. Sci., 26, 3025–3043, https://doi.org/10.5194/nhess-26-3025-2026, https://doi.org/10.5194/nhess-26-3025-2026, 2026
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This study investigates the hydrometeorological features of the major floods of 2008, 2010, and 2020 in western Ukraine. All cases were linked to upper-level potential vorticity (PV) anomalies. We also conducted a climatological analysis of PV structure associated with 22 summer heavy precipitation events (2000–2022), highlighting their key role in determining the location and intensity of flood-inducing rainfall events in the Carpathians.
Alexander Pietak, Langwen Huang, Luigi Fusco, Michael Sprenger, Sebastian Schemm, and Torsten Hoefler
Geosci. Model Dev., 19, 3893–3922, https://doi.org/10.5194/gmd-19-3893-2026, https://doi.org/10.5194/gmd-19-3893-2026, 2026
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As meteorological models grow in complexity, the volume of output data increases, making compression increasingly desirable. However, no specialized methods currently exist for compressing data in the Lagrangian frame. To address this gap, we developed psit, a pipeline for the lossy compression of Lagrangian flow data. In most cases, psit achieves performance that is equivalent or superior to non specialized alternatives, with compression errors behaving similar to measurement inaccuracies.
Huw C. Davies and Michael A. Sprenger
Weather Clim. Dynam., 7, 717–741, https://doi.org/10.5194/wcd-7-717-2026, https://doi.org/10.5194/wcd-7-717-2026, 2026
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The Stratospheric Polar Vortex with its strong circumpolar jet is a dominant feature of the wintertime stratosphere. Evidence is presented of the characteristics of its distinctive sub-planetary scale features. The scale and dynamics of the features are linked to the break-up of an annular band of strong vorticity at the vortex's periphery, and moreover its aggregation into one or two vortices due to forcing from below can have ramifications for the occurrence of Sudden Stratospheric Warmings.
Marius Rixen, Praveen Pothapakula, Michael Sprenger, Christian Zeman, and Andreas F. Prein
EGUsphere, https://doi.org/10.5194/egusphere-2026-1814, https://doi.org/10.5194/egusphere-2026-1814, 2026
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Despite steady improvements in forecasting skill, episodes of low forecast skill, called forecast busts, still persist. Using global ensemble simulations at different grid spacings, we show that coarse-grid simulations fail to resolve key mesoscale diabatic processes, and that errors upscale and propagate downstream, leading to large forecast errors. Fine grid spacing simulations better capture scale interactions in strongly diabatic flow, highlighting the potential of kilometer-scale models.
Tuule Müürsepp, Michael Sprenger, Heini Wernli, and Hanna Joos
Weather Clim. Dynam., 7, 547–565, https://doi.org/10.5194/wcd-7-547-2026, https://doi.org/10.5194/wcd-7-547-2026, 2026
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The tropopause region of the atmosphere is greatly impacted by the exchange of mass and constituents between the troposphere and the stratosphere. This study quantifies the role of radiation in troposphere-to-stratosphere transport using reanalysis data. We find that radiation contributes to this transport most of the time, albeit it might not be the dominant process. We provide a new insight into the complex interplay of processes that air parcels experience on their way to the stratosphere.
Stefania Gilardoni, Annachiara Bellini, Paolo Bonasoni, Henry Diémoz, Christian Gencarelli, Angela Marinoni, Eros Mariani, Luigi Mazari Villanova, Bruno Neininger, Mattia Perilli, Michael Sprenger, and Francesco Petracchini
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Franziska Schnyder, Ming Hon Franco Lee, and Heini Wernli
Weather Clim. Dynam., 6, 1319–1337, https://doi.org/10.5194/wcd-6-1319-2025, https://doi.org/10.5194/wcd-6-1319-2025, 2025
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Killian P. Brennan, Michael Sprenger, André Walser, Marco Arpagaus, and Heini Wernli
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Marc Federer, Lukas Papritz, Michael Sprenger, and Christian M. Grams
Weather Clim. Dynam., 6, 211–230, https://doi.org/10.5194/wcd-6-211-2025, https://doi.org/10.5194/wcd-6-211-2025, 2025
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Philip Rupp, Jonas Spaeth, Hilla Afargan-Gerstman, Dominik Büeler, Michael Sprenger, and Thomas Birner
Weather Clim. Dynam., 5, 1287–1298, https://doi.org/10.5194/wcd-5-1287-2024, https://doi.org/10.5194/wcd-5-1287-2024, 2024
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Katharina Heitmann, Michael Sprenger, Hanin Binder, Heini Wernli, and Hanna Joos
Weather Clim. Dynam., 5, 537–557, https://doi.org/10.5194/wcd-5-537-2024, https://doi.org/10.5194/wcd-5-537-2024, 2024
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Lukas Jansing, Lukas Papritz, and Michael Sprenger
Weather Clim. Dynam., 5, 463–489, https://doi.org/10.5194/wcd-5-463-2024, https://doi.org/10.5194/wcd-5-463-2024, 2024
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Using an innovative approach, the descent of foehn is diagnosed from a Lagrangian perspective based on 15 kilometer-scale simulations combined with online trajectories. The descent is confined to distinct hotspots in the immediate lee of local mountain peaks and chains. Two detailed case studies reveal a varying wave regime to be associated with the descent. Furthermore, additional controlling factors, such as the diurnal cycle, likewise influence the descent activity.
Hilla Afargan-Gerstman, Dominik Büeler, C. Ole Wulff, Michael Sprenger, and Daniela I. V. Domeisen
Weather Clim. Dynam., 5, 231–249, https://doi.org/10.5194/wcd-5-231-2024, https://doi.org/10.5194/wcd-5-231-2024, 2024
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The stratosphere is a layer of Earth's atmosphere found above the weather systems. Changes in the stratosphere can affect the winds and the storm tracks in the North Atlantic region for a relatively long time, lasting for several weeks and even months. We show that the stratosphere can be important for weather forecasts beyond 1 week, but more work is needed to improve the accuracy of these forecasts for 3–4 weeks.
Yonatan Givon, Or Hess, Emmanouil Flaounas, Jennifer Louise Catto, Michael Sprenger, and Shira Raveh-Rubin
Weather Clim. Dynam., 5, 133–162, https://doi.org/10.5194/wcd-5-133-2024, https://doi.org/10.5194/wcd-5-133-2024, 2024
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A novel classification of Mediterranean cyclones is presented, enabling a separation between storms driven by different atmospheric processes. The surface impact of each cyclone class differs greatly by precipitation, winds, and temperatures, providing an invaluable tool to study the climatology of different types of Mediterranean storms and enhancing the understanding of their predictability, on both weather and climate scales.
Stefania Gilardoni, Dominic Heslin-Rees, Mauro Mazzola, Vito Vitale, Michael Sprenger, and Radovan Krejci
Atmos. Chem. Phys., 23, 15589–15607, https://doi.org/10.5194/acp-23-15589-2023, https://doi.org/10.5194/acp-23-15589-2023, 2023
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Models still fail in reproducing black carbon (BC) temporal variability in the Arctic. Analysis of equivalent BC concentrations in the European Arctic shows that BC seasonal variability is modulated by the efficiency of removal by precipitation during transport towards high latitudes. Short-term variability is controlled by synoptic-scale circulation patterns. The advection of warm air from lower latitudes is an effective pollution transport pathway during summer.
Thomas Trickl, Martin Adelwart, Dina Khordakova, Ludwig Ries, Christian Rolf, Michael Sprenger, Wolfgang Steinbrecht, and Hannes Vogelmann
Atmos. Meas. Tech., 16, 5145–5165, https://doi.org/10.5194/amt-16-5145-2023, https://doi.org/10.5194/amt-16-5145-2023, 2023
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Tropospheric ozone have been measured for more than a century. Highly quantitative ozone measurements have been made at monitoring stations. However, deficits have been reported for vertical sounding systems. Here, we report a thorough intercomparison effort between a differential-absorption lidar system and two types of balloon-borne ozone sondes, also using ozone sensors at nearby mountain sites as references. The sondes agree very well with the lidar after offset corrections.
Melanie Lauer, Annette Rinke, Irina Gorodetskaya, Michael Sprenger, Mario Mech, and Susanne Crewell
Atmos. Chem. Phys., 23, 8705–8726, https://doi.org/10.5194/acp-23-8705-2023, https://doi.org/10.5194/acp-23-8705-2023, 2023
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We present a new method to analyse the influence of atmospheric rivers (ARs), cyclones, and fronts on the precipitation in the Arctic, based on two campaigns: ACLOUD (early summer 2017) and AFLUX (early spring 2019). There are differences between both campaign periods: in early summer, the precipitation is mostly related to ARs and fronts, especially when they are co-located, while in early spring, cyclones isolated from ARs and fronts contributed most to the precipitation.
Emmanouil Flaounas, Leonardo Aragão, Lisa Bernini, Stavros Dafis, Benjamin Doiteau, Helena Flocas, Suzanne L. Gray, Alexia Karwat, John Kouroutzoglou, Piero Lionello, Mario Marcello Miglietta, Florian Pantillon, Claudia Pasquero, Platon Patlakas, María Ángeles Picornell, Federico Porcù, Matthew D. K. Priestley, Marco Reale, Malcolm J. Roberts, Hadas Saaroni, Dor Sandler, Enrico Scoccimarro, Michael Sprenger, and Baruch Ziv
Weather Clim. Dynam., 4, 639–661, https://doi.org/10.5194/wcd-4-639-2023, https://doi.org/10.5194/wcd-4-639-2023, 2023
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Cyclone detection and tracking methods (CDTMs) have different approaches in defining and tracking cyclone centers. This leads to disagreements on extratropical cyclone climatologies. We present a new approach that combines tracks from individual CDTMs to produce new composite tracks. These new tracks are shown to correspond to physically meaningful systems with distinctive life stages.
Hanna Joos, Michael Sprenger, Hanin Binder, Urs Beyerle, and Heini Wernli
Weather Clim. Dynam., 4, 133–155, https://doi.org/10.5194/wcd-4-133-2023, https://doi.org/10.5194/wcd-4-133-2023, 2023
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Warm conveyor belts (WCBs) are strongly ascending, cloud- and precipitation-forming airstreams in extratropical cyclones. In this study we assess their representation in a climate simulation and their changes under global warming. They become moister, become more intense, and reach higher altitudes in a future climate, implying that they potentially have an increased impact on the mid-latitude flow.
Andreas Schäfler, Michael Sprenger, Heini Wernli, Andreas Fix, and Martin Wirth
Atmos. Chem. Phys., 23, 999–1018, https://doi.org/10.5194/acp-23-999-2023, https://doi.org/10.5194/acp-23-999-2023, 2023
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In this study, airborne lidar profile measurements of H2O and O3 across a midlatitude jet stream are combined with analyses in tracer–trace space and backward trajectories. We highlight that transport and mixing processes in the history of the observed air masses are governed by interacting tropospheric weather systems on synoptic timescales. We show that these weather systems play a key role in the high variability of the paired H2O and O3 distributions near the tropopause.
Hanin Binder, Hanna Joos, Michael Sprenger, and Heini Wernli
Weather Clim. Dynam., 4, 19–37, https://doi.org/10.5194/wcd-4-19-2023, https://doi.org/10.5194/wcd-4-19-2023, 2023
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Warm conveyor belts (WCBs) are the main cloud- and precipitation-producing airstreams in extratropical cyclones. The latent heat release that occurs during cloud formation often contributes to the intensification of the associated cyclone. Based on the Community Earth System Model Large Ensemble coupled climate simulations, we show that WCBs and associated latent heating will become stronger in a future climate and be even more important for explosive cyclone intensification than in the present.
Michael A. Barnes, Thando Ndarana, Michael Sprenger, and Willem A. Landman
Weather Clim. Dynam., 3, 1291–1309, https://doi.org/10.5194/wcd-3-1291-2022, https://doi.org/10.5194/wcd-3-1291-2022, 2022
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Stratospheric air can intrude into the troposphere and is associated with cyclonic development throughout the atmosphere. Through a highly idealized systematic approach, the effect that different intrusion characteristics have on surface cyclogenetic forcing is investigated. The proximity of stratospheric intrusions to the surface is shown to be the main factor in surface cyclogenetic forcing, whilst its width is an additional contributing factor.
Lukas Jansing, Lukas Papritz, Bruno Dürr, Daniel Gerstgrasser, and Michael Sprenger
Weather Clim. Dynam., 3, 1113–1138, https://doi.org/10.5194/wcd-3-1113-2022, https://doi.org/10.5194/wcd-3-1113-2022, 2022
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This study presents a 5-year climatology of three main foehn types and three deep-foehn subtypes. The main types differ in their large-scale and Alpine-scale weather conditions and the subtypes in terms of the amount and extent of precipitation on the Alpine south side. The different types of foehn are found to strongly affect the local meteorological conditions at Altdorf. The study concludes by setting the new classification into a historic context.
Jan Clemens, Felix Ploeger, Paul Konopka, Raphael Portmann, Michael Sprenger, and Heini Wernli
Atmos. Chem. Phys., 22, 3841–3860, https://doi.org/10.5194/acp-22-3841-2022, https://doi.org/10.5194/acp-22-3841-2022, 2022
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Highly polluted air flows from the surface to higher levels of the atmosphere during the Asian summer monsoon. At high levels, the air is trapped within eddies. Here, we study how air masses can leave the eddy within its cutoff, how they distribute, and how their chemical composition changes. We found evidence for transport from the eddy to higher latitudes over the North Pacific and even Alaska. During transport, trace gas concentrations within cutoffs changed gradually, showing steady mixing.
Jörg Wieder, Claudia Mignani, Mario Schär, Lucie Roth, Michael Sprenger, Jan Henneberger, Ulrike Lohmann, Cyril Brunner, and Zamin A. Kanji
Atmos. Chem. Phys., 22, 3111–3130, https://doi.org/10.5194/acp-22-3111-2022, https://doi.org/10.5194/acp-22-3111-2022, 2022
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We investigate the variation in ice-nucleating particles (INPs) relevant for primary ice formation in mixed-phased clouds over the Alps based on simultaneous in situ observations at a mountaintop and a nearby high valley (1060 m height difference). In most cases, advection from the surrounding lower regions was responsible for changes in INP concentration, causing a diurnal cycle at the mountaintop. Our study underlines the importance of the planetary boundary layer as an INP reserve.
Lukas Bösiger, Michael Sprenger, Maxi Boettcher, Hanna Joos, and Tobias Günther
Geosci. Model Dev., 15, 1079–1096, https://doi.org/10.5194/gmd-15-1079-2022, https://doi.org/10.5194/gmd-15-1079-2022, 2022
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Jet streams are coherent air flows that interact with atmospheric structures such as warm conveyor belts (WCBs) and the tropopause. Individually, these structures have a significant impact on the weather evolution. A first step towards a deeper understanding of the meteorological processes is to extract jet stream core lines, for which we develop a novel feature extraction algorithm. Based on the line geometry, we automatically detect and visualize potential interactions between WCBs and jets.
Philippe Besson, Luise J. Fischer, Sebastian Schemm, and Michael Sprenger
Weather Clim. Dynam., 2, 991–1009, https://doi.org/10.5194/wcd-2-991-2021, https://doi.org/10.5194/wcd-2-991-2021, 2021
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The strongest cyclone intensification is associated with a strong dry-dynamical forcing. Moreover, strong forcing and strong intensification correspond to a tendency for poleward cyclone propagation, which occurs in distinct regions in the Northern Hemisphere. There is a clear spatial pattern in the occurrence of certain forcing combinations. This implies a fundamental relationship between dry-dynamical processes and the intensification as well as the propagation of extratropical cyclones.
Cited articles
Bannon, J. K.: Meteorological aspects of turbulence affecting aircraft at high altitude, Tech. Rep. Professional Notes No. 104, Meteorological Office, https://digital.nmla.metoffice.gov.uk/IO_9d123c55-1919-4ebd-8515-ba2f0cc13dab/ (last access: 22 October 2025), 1951. a
Brown, R.: New indices to locate clear-air turbulence, Meteor. Mag, 102, 347–361, 1973. a
Browning, K. A., Hardman, M. E., Harrold, T. W., and Pardoe, C. W.: The structure of rainbands within a mid‐latitude depression, Q. J. Roy. Meteor. Soc., 99, 215–231, https://doi.org/10.1002/QJ.49709942002, 1973. a
Chambers, E.: Clear air turbulence and civil jet operations, J. R. Aeronaut. Soc., 59, 613–628, https://doi.org/10.1017/S036839310011692X, 1955. a
Dutton, J. A. and Panofsky, H. A.: Clear air turbulence: a mystery may be unfolding, Science, 167, 937–944, https://doi.org/10.1126/science.167.3920.937, 1970. a
Ellrod, G. P., Knox, J. A., Lester, P. F., and Ehernberger, L. J.: Aviation meteorology | Clear air turbulence, in: Encyclopedia of Atmospheric Sciences, edited by: North, G. R., Pyle, J., and Zhang, F., Academic Press, 2nd edn., 177–186, https://doi.org/10.1016/B978-0-12-382225-3.00104-3, ISBN 978-0-12-382225-3, 2015. a
Endlich, R. M.: The mesoscale structure of some regions of clear-air turbulence, J. Appl. Meteorol., 3, 261–276, https://doi.org/10.1175/1520-0450(1964)003<0261:tmsosr>2.0.co;2, 1964. a, b, c
Endlich, R. M. and McLean, G. S.: Empirical relationships between gust intensity in clear-air turbulence and certain meteorological quantities, J. Appl. Meteorol. Clim., 4, 222–227, https://doi.org/10.1175/1520-0450(1965)004<0222:ERBGII>2.0.CO;2, 1965. a
Ester, M., Kriegel, H.-P., Sander, J., and Xu, X.: A density-based algorithm for discovering clusters in large spatial databases with noise, in: Proceedings of the Second International Conference on Knowledge Discovery and Data Mining, KDD'96, AAAI Press, 226–231, https://dl.acm.org/doi/10.5555/3001460.3001507 (last access: 22 October 2025), 1996. a, b, c
Foudad, M., Sanchez-Gomez, E., Jaravel, T., Rochoux, M. C., and Terray, L.: Past and future trends in clear-air turbulence over the Northern Hemisphere, Geophys. Res.-Atmos., 129, e2023JD040261, https://doi.org/10.1029/2023JD040261, 2024. a, b
Goecke, T. and Machulskaya, E.: Aviation turbulence forecasting at DWD with ICON: Methodology, case studies, and verification, Mon. Weather Rev., 149, 2115–2130, https://doi.org/10.1175/MWR-D-19-0383.1, 2021. a
Harvey, B., Methven, J., Sanchez, C., and Schäfler, A.: Diabatic generation of negative potential vorticity and its impact on the North Atlantic jet stream, Q. J. Roy. Meteor. Soc., 146, 1477–1497, https://doi.org/10.1002/QJ.3747, 2020. a, b
Heitmann, K., Sprenger, M., Binder, H., Wernli, H., and Joos, H.: Warm conveyor belt characteristics and impacts along the life cycle of extratropical cyclones: case studies and climatological analysis based on ERA5, Weather Clim. Dynam., 5, 537–557, https://doi.org/10.5194/wcd-5-537-2024, 2024. a, b
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R., Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L., Healy, S., Hogan, R. J., Hólm, E., Janisková, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum, I., Vamborg, F., Villaume, S., and Thépaut, J.-N.: Complete ERA5 from 1940: Fifth generation of ECMWF atmospheric reanalyses of the global climate, Copernicus Climate Change Service (C3S) Data Store (CDS) [data set], https://doi.org/10.24381/cds.143582cf, 2017. a
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R., Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L., Healy, S., Hogan, R. J., Hólm, E., Janisková, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum, I., Vamborg, F., Villaume, S., and Thépaut, J.-N.: The ERA5 global reanalysis, Q. J. Roy. Meteor. Soc., 146, 1999–2049, https://doi.org/10.1002/qj.3803, 2020. a, b
Hislop, G. S.: Clear air turbulence over Europe, J. R. Aeronaut. Soc., 55, 185–225, https://doi.org/10.1017/S0001924000132713, 1951. a, b, c
Jaeger, E. B. and Sprenger, M.: A Northern Hemispheric climatology of indices for clear air turbulence in the tropopause region derived from ERA40 reanalysis data, Geophys. Res.-Atmos., 112, D20106, https://doi.org/10.1029/2006JD008189, 2007. a
Janowiak, J., Joyce, B., and Xie, P.: NCEP/CPC L3 half hourly 4km global (60S - 60N) merged IR V1, edited by: Savtchenko, A., Goddard Earth Sciences Data and Information Services Center (GES DISC) [data set], Greenbelt, MD, https://doi.org/10.5067/P4HZB9N27EKU, 2017. a, b, c
Joos, H., Sprenger, M., Binder, H., Beyerle, U., and Wernli, H.: Warm conveyor belts in present-day and future climate simulations – Part 1: Climatology and impacts, Weather Clim. Dynam., 4, 133–155, https://doi.org/10.5194/wcd-4-133-2023, 2023. a
Knox, J. A.: Possible mechanisms of clear-air turbulence in strongly anticyclonic flows, Mon. Weather Rev., 125, 1251–1259, https://doi.org/10.1175/1520-0493(1997)125<1251:PMOCAT>2.0.CO;2, 1997. a, b, c, d
Knox, J. A., McCann, D. W., and Williams, P. D.: Application of the Lighthill–Ford Theory of Spontaneous Imbalance to Clear-Air Turbulence Forecasting, J. Atmos. Sci., 65, 3292–3304, https://doi.org/10.1175/2008JAS2477.1, 2008. a
Koch, P., Wernli, H., and Davies, H. C.: An event-based jet-stream climatology and typology, Int. J. Climatol., 26, 283–301, https://doi.org/10.1002/joc.1255, 2006. a
Koch, S. E., Jamison, B. D., Lu, C., Smith, T. L., Tollerud, E. I., Girz, C., Wang, N., Lane, T. P., Shapiro, M. A., Parrish, D. D., and Cooper, O. R.: Turbulence and gravity waves within an upper-level front, J. Atmos. Sci., 62, 3885–3908, https://doi.org/10.1175/JAS3574.1, 2005. a
Lane, T. P., Doyle, J. D., Plougonven, R., Shapiro, M. A., and Sharman, R. D.: Observations and numerical simulations of inertia-gravity waves and shearing instabilities in the vicinity of a jet stream, J. Atmos. Sci., 61, 2692–2706, https://doi.org/10.1175/JAS3305.1, 2004. a
Lane, T. P., Sharman, R. D., Trier, S. B., Fovell, R. G., and Williams, J. K.: Recent advances in the understanding of near-cloud turbulence, B. Am. Meteorol. Soc., 93, 499–515, https://doi.org/10.1175/BAMS-D-11-00062.1, 2012. a, b
Lee, D. B. and Chun, H. Y.: A numerical study of aviation turbulence encountered on 13 February 2013 over the Yellow Sea between China and the Korean Peninsula, J. Appl. Meteorol. Clim., 57, 1043–1060, https://doi.org/10.1175/JAMC-D-17-0247.1, 2018. a
Lee, D. R., Stull, R. S., and Irvine, W. S.: Clear air turbulence forecasting techniques, Tech. rep., Air Force Global Weather Central, Offutt AFB NE 68113, https://apps.dtic.mil/sti/citations/ADA144854 (last access: 22 October 2025), 1984. a
Lee, J. H., Kim, J. H., Sharman, R. D., Kim, J., and Son, S. W.: Climatology of clear-air turbulence in upper troposphere and lower stratosphere in the Northern Hemisphere using ERA5 reanalysis data, Geophys. Res.-Atmos., 128, e2022JD037679, https://doi.org/10.1029/2022JD037679, 2023. a, b, c
Lee, M. H. F.: Rossby wave breaking in present and end-of-century climate, Master thesis, ETH Zurich, Zurich, https://doi.org/10.3929/ethz-b-000564088, 2022. a
Lojko, A., Winters, A. C., Oertel, A., Jablonowski, C., and Payne, A. E.: An ERA5 climatology of synoptic-scale negative potential vorticity–jet interactions over the western North Atlantic, Weather Clim. Dynam., 6, 387–411, https://doi.org/10.5194/wcd-6-387-2025, 2025. a
Madonna, E., Wernli, H., Joos, H., and Martius, O.: Warm conveyor belts in the ERA-Interim Dataset (1979–2010). Part I: Climatology and potential vorticity evolution, J. Climate, 27, 3–26, https://doi.org/10.1175/JCLI-D-12-00720.1, 2014. a, b
Mancuso, R. L. and Endlich, R. M.: Clear air turbulence frequency as a function of wind shear and deformation, Mon. Weather Rev., 94, 581–585, https://doi.org/10.1175/1520-0493(1966)094<0581:catfaa>2.3.co;2, 1966. a, b
Martius, O. and Rivière, G.: Rossby wave breaking: climatology, interaction with low-frequency climate variability, and links to extreme weather events, in: Dynamics and predictability of large-scale, high-impact weather and climate events, edited by: Li, J., Swinbank, R., Grotjahn, R., and Volkert, H., Special Publications of the International Union of Geodesy and Geophysics, Cambridge University Press, 69–78, https://doi.org/10.1017/CBO9781107775541.006, 2016. a
Meymaris, G., Sharman, R., Cornman, L. B., and Deierling, W.: The NCAR in situ turbulence detection algorithm, Tech. rep., National Center for Atmospheric Research, https://doi.org/10.5065/G24Q-EA27, 2019. a, b
NOAA, NASA, and USAF: U.S. standard atmosphere, 1976, Tech. rep., National Oceanic and Atmospheric Administration, National Aeronautics and Space Administration, United States Air Force, Washington, D.C., https://ntrs.nasa.gov/citations/19770009539 (last access: 22 October 2025), 1976. a
Oertel, A., Boettcher, M., Joos, H., Sprenger, M., and Wernli, H.: Potential vorticity structure of embedded convection in a warm conveyor belt and its relevance for large-scale dynamics, Weather Clim. Dynam., 1, 127–153, https://doi.org/10.5194/wcd-1-127-2020, 2020. a, b
Reiter, E. R.: The nature of clear air turbulence: a review, in: Clear air turbulence and its detection, edited by: Pao, Y. H. and Goldburg, A., Springer US, 7–33, https://doi.org/10.1007/978-1-4899-5615-6_2, ISBN 978-1-4899-5615-6, 1969. a
Reiter, E. R. and Nania, A.: Jet-stream structure and clear-air turbulence (CAT), J. Appl. Meteorol., 3, 247–260, https://doi.org/10.1175/1520-0450(1964)003<0247:jssaca>2.0.co;2, 1964. a
Roach, W. T.: On the influence of synoptic development on the production of high level turbulence, Q. J. Roy. Meteor. Soc., 96, 413–429, https://doi.org/10.1002/QJ.49709640906, 1970. a
Rodriguez Imazio, P., Dörnbrack, A., Urzua, R. D., Rivaben, N., and Godoy, A.: Clear air turbulence observed across a tropopause fold over the Drake Passage – a case study, Geophys. Res.-Atmos., 127, e2021JD035908, https://doi.org/10.1029/2021JD035908, 2022. a
Rustenbeck, J. D.: The association of Richardson's criterion with high level turbulence, Mon. Weather Rev., 91, 193–198, https://doi.org/10.1175/1520-0493(1963)091<0193:TAORCW>2.3.CO;2, 1963. a
Schultz, D. M. and Schumacher, P. N.: The use and misuse of conditional symmetric instability, Mon. Weather Rev., 127, 2709–2732, https://doi.org/10.1175/1520-0493(1999)127<2709:TUAMOC>2.0.CO;2, 1999. a
Schwartz, B.: The quantitative use of PIREPs in developing aviation weather guidance products, Weather Forecast., 11, 372–384, https://doi.org/10.1175/1520-0434(1996)011<0372:TQUOPI>2.0.CO;2, 1996. a
Shao, J., Zhang, J., Wang, W., Zhang, S., Yu, T., and Dong, W.: Occurrence frequency of subcritical Richardson numbers assessed by global high-resolution radiosonde and ERA5 reanalysis, Atmos. Chem. Phys., 23, 12589–12607, https://doi.org/10.5194/acp-23-12589-2023, 2023. a
Sharman, R., Tebaldi, C., Wiener, G., and Wolff, J.: An integrated approach to mid- and upper-level turbulence forecasting, Weather Forecast., 21, 268–287, https://doi.org/10.1175/WAF924.1, 2006. a, b, c, d
Sharman, R., Lane, T., and Schumann, U.: Research needs, in: Aviation turbulence: processes, detection, prediction, edited by: Sharman, R. and Lane, T., Springer International Publishing, 501–518, https://doi.org/10.1007/978-3-319-23630-8_25, ISBN 9783319236308, 2016. a
Sharman, R. D. and Pearson, J. M.: Prediction of energy dissipation rates for aviation turbulence. Part I: Forecasting nonconvective turbulence, J. Appl. Meteorol. Clim., 56, 317–337, https://doi.org/10.1175/JAMC-D-16-0205.1, 2017. a
Smith, I. H., Williams, P. D., and Schiemann, R.: Clear-air turbulence trends over the North Atlantic in high-resolution climate models, Clim. Dynam., 61, 3063–3079, https://doi.org/10.1007/s00382-023-06694-x, 2023. a
Spensberger, C. and Spengler, T.: A new look at deformation as a diagnostic for large-scale flow, J. Atmos. Sci., 71, 4221–4234, https://doi.org/10.1175/JAS-D-14-0108.1, 2014. a
Sprenger, M., Fragkoulidis, G., Binder, H., Croci-Maspoli, M., Graf, P., Grams, C. M., Knippertz, P., Madonna, E., Schemm, S., Škerlak, B., and Wernli, H.: Global climatologies of Eulerian and Lagrangian flow features based on ERA-Interim, B. Am. Meteorol. Soc., 98, 1739–1748, https://doi.org/10.1175/BAMS-D-15-00299.1, 2017. a, b
Thompson, C. F. and Schultz, D. M.: The release of inertial instability near an idealized zonal jet, Geophys. Res. Lett., 48, https://doi.org/10.1029/2021GL092649, 2021. a
Thompson, C. F., Schultz, D. M., and Vaughan, G.: A global climatology of tropospheric inertial instability, J. Atmos. Sci., 75, 805–825, https://doi.org/10.1175/JAS-D-17-0062.1, 2018. a
Trier, S. B. and Sharman, R. D.: Mechanisms influencing cirrus banding and aviation turbulence near a convectively enhanced upper-level jet stream, Mon. Weather Rev., 144, 3003–3027, https://doi.org/10.1175/MWR-D-16-0094.1, 2016. a, b, c
Trier, S. B., Sharman, R. D., and Lane, T. P.: Influences of moist convection on a cold-season outbreak of clear-air turbulence (CAT), Mon. Weather Rev., 140, 2477–2496, https://doi.org/10.1175/MWR-D-11-00353.1, 2012. a
Trier, S. B., Sharman, R. D., Muñoz-Esparza, D., and Lane, T. P.: Environment and mechanisms of severe turbulence in a midlatitude cyclone, J. Atmos. Sci., 77, 3869–3889, https://doi.org/10.1175/JAS-D-20-0095.1, 2020. a, b, c
Trier, S. B., Sharman, R. D., Muñoz-Esparza, D., and Keller, T. L.: Effects of distant organized convection on forecasts of widespread clear-air turbulence, Mon. Weather Rev., 150, 2593–2615, https://doi.org/10.1175/MWR-D-22-0077.1, 2022. a
Wernli, H. and Sprenger, M.: Identification and ERA-15 climatology of potential vorticity streamers and cutoffs near the extratropical tropopause, J. Atmos. Sci., 64, 1569–1586, https://doi.org/10.1175/JAS3912.1, 2007. a, b
Williams, P. D.: Increased light, moderate, and severe clear-air turbulence in response to climate change, Adv. Atmos. Sci., 34, 576–586, https://doi.org/10.1007/S00376-017-6268-2, 2017. a
Williams, P. D. and Joshi, M. M.: Intensification of winter transatlantic aviation turbulence in response to climate change, Nat. Clim. Change, 3, 644–648, https://doi.org/10.1038/nclimate1866, 2013. a
Wolff, J. K. and Sharman, R. D.: Climatology of upper-level turbulence over the contiguous United States, J. Appl. Meteorol. Clim., 47, 2198–2214, https://doi.org/10.1175/2008JAMC1799.1, 2008. a
Editorial statement
In this study, a novel climatological analysis of the linkage between clear air turbulence and synoptic weather features is presented based on a combination of aircraft measurements and feature detection in reanalysis data. Detailed hypotheses are put forward on the physical processes leading to the generation of turbulence in the vicinity of Rossby wave breaking and warm conveyor belts. The results can be useful for aviation safety and turbulence forecasting in operational settings, but also for future research into the fundamental mechanisms behind clear air turbulence and its spatio-temporal variability.
In this study, a novel climatological analysis of the linkage between clear air turbulence and...
Short summary
Turbulence can occur in clear-air conditions at cruising altitude. From around 5000 clear-air turbulence events identified using aircraft measurements, nonlinear breaking of large-scale waves and rapidly ascending airstreams associated with cyclones are found concurrent with 40 % and 30 % of them respectively. The results further show that these weather systems may trigger turbulence by generating highly deformed flow or flow instability, improving our understanding of clear-air turbulence.
Turbulence can occur in clear-air conditions at cruising altitude. From around 5000 clear-air...
