Articles | Volume 2, issue 4
https://doi.org/10.5194/wcd-2-1073-2021
© Author(s) 2021. 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-2-1073-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
09 Nov 2021
Research article |
| 09 Nov 2021
| 09 Nov 2021
Systematic assessment of the diabatic processes that modify low-level potential vorticity in extratropical cyclones
Roman Attinger
CORRESPONDING AUTHOR
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
present address: Swiss Federal Office of Meteorology and Climatology, MeteoSwiss, Zurich, Switzerland
Elisa Spreitzer
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Maxi Boettcher
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Heini Wernli
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Hanna Joos
Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Related authors
No articles found.
Killian P. Brennan, Iris Thurnherr, Michael Sprenger, and Heini Wernli
Nat. Hazards Earth Syst. Sci., 25, 3693–3712, https://doi.org/10.5194/nhess-25-3693-2025, https://doi.org/10.5194/nhess-25-3693-2025, 2025
Short summary
Short summary
Hailstorms can cause severe damage to homes, crops, and infrastructure. Using high-resolution climate simulations, we tracked thousands of hailstorms across Europe to study future changes. Large hail will become more frequent, hail-covered areas will expand, and instances of extreme hail combined with heavy rain will double. These shifts could increase risks for communities and businesses, highlighting the need for better preparedness and adaptation.
Luise J. Fischer, David N. Bresch, Dominik Büeler, Christian M. Grams, Robin Noyelle, Matthias Röthlisberger, and Heini Wernli
Weather Clim. Dynam., 6, 1027–1043, https://doi.org/10.5194/wcd-6-1027-2025, https://doi.org/10.5194/wcd-6-1027-2025, 2025
Short summary
Short summary
Atmospheric flows over the North Atlantic can be meaningfully classified into weather regimes, and climate simulations suggest that the regime frequencies might change in the future. We provide a quantitative framework that helps assess whether these regime frequency changes are relevant to understanding climate change signals in precipitation. At least in our example application, in most regions, regime frequency changes explain little of the projected precipitation changes.
Katharina Hartmuth, Dominik Büeler, and Heini Wernli
EGUsphere, https://doi.org/10.5194/egusphere-2025-4111, https://doi.org/10.5194/egusphere-2025-4111, 2025
Short summary
Short summary
This study presents three case studies of applying a newly developed method to quantify the uncertainty of the operational ECMWF ensemble in forecasting precipitation and wind extremes associated with Mediterranean cyclones. We find that the cyclones as well as their associated extremes are predicted well for lead times ≤48 h; however, for longer lead times there is large case-to-case variability in the ensemble performance.
Nora Zilibotti, Heini Wernli, and Sebastian Schemm
EGUsphere, https://doi.org/10.5194/egusphere-2025-3605, https://doi.org/10.5194/egusphere-2025-3605, 2025
Short summary
Short summary
This study investigates the relationship between jet strength and storm track activity in the North Pacific and North Atlantic with a new approach that does not rely on monthly averaging. We find a consistent behaviour in the two basins, with two distinct relationships on seasonal and sub-monthly timescales emerging. This work underlines the importance of separating different timescales of variability to understand the interplay of jet characteristics and storm track activity.
Killian P. Brennan, Michael Sprenger, André Walser, Marco Arpagaus, and Heini Wernli
Weather Clim. Dynam., 6, 645–668, https://doi.org/10.5194/wcd-6-645-2025, https://doi.org/10.5194/wcd-6-645-2025, 2025
Short summary
Short summary
We studied severe hailstorms that occurred in Switzerland on 28 June 2021 using a weather prediction model to understand how they evolved. We found that the storms moved toward areas with more storm energy. Hailfall was quickly followed by heavy rain. Just before the storms died out, the air feeding them stopped coming from near the ground. We also observed a delay between different types of precipitation forming in the incoming air.
Katharina Hartmuth, Heini Wernli, and Lukas Papritz
Weather Clim. Dynam., 6, 505–520, https://doi.org/10.5194/wcd-6-505-2025, https://doi.org/10.5194/wcd-6-505-2025, 2025
Short summary
Short summary
In this study, we use large-ensemble climate model simulations to analyze extreme winters in the Barents Sea in a changing climate. We find that variability in both atmospheric processes and sea ice conditions determines the formation of such seasons in the present-day climate. The reduction in sea ice variability results in a decreasing importance of surface boundary conditions in a warmer climate, while the robust link shown for surface weather systems persists.
Franziska Schnyder, Ming Hon Franco Lee, and Heini Wernli
EGUsphere, https://doi.org/10.5194/egusphere-2025-1724, https://doi.org/10.5194/egusphere-2025-1724, 2025
Short summary
Short summary
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.
Selvakumar Vishnupriya, Michael Sprenger, Hanna Joos, and Heini Wernli
EGUsphere, https://doi.org/10.5194/egusphere-2025-1731, https://doi.org/10.5194/egusphere-2025-1731, 2025
Short summary
Short summary
Extratropical cyclones feature rapidly ascending airstreams known as warm conveyor belts, which influence upper-level flow dynamics. This study classifies interactions of warm conveyor belts with the jet stream into four types: no interactions, ridges, blocks, and tropospheric cutoffs. We use reanalysis data to show that the interaction type depends more on the structure of the ambient flow than on the WCB properties, which improves the understanding of extratropical flow variability.
Nicolai Krieger, Heini Wernli, Michael Sprenger, and Christian Kühnlein
Weather Clim. Dynam., 6, 447–469, https://doi.org/10.5194/wcd-6-447-2025, https://doi.org/10.5194/wcd-6-447-2025, 2025
Short summary
Short summary
This study investigates the Laseyer, a local windstorm in a narrow Swiss valley characterized by strong southeasterly winds during northwesterly ambient flow. Using large-eddy simulations (LESs) with 30 m grid spacing, this is the first study to reveal that the extreme gusts in the valley are caused by an amplifying interplay of two recirculation regions. Modifying terrain and ambient wind conditions affects the windstorm's intensity and highlights the importance of topographic details in LES.
Hanin Binder and Heini Wernli
Weather Clim. Dynam., 6, 151–170, https://doi.org/10.5194/wcd-6-151-2025, https://doi.org/10.5194/wcd-6-151-2025, 2025
Short summary
Short summary
This study presents a systematic analysis of frequency anomalies and characteristics of extratropical cyclones during extremely wet, dry, windy, and calm winter and summer seasons in the extratropics based on 1050 years of present-day climate simulations. We show that anomalies in cyclone frequency, intensity, and stationarity are crucial to the occurrence of many extreme seasons and that these anomaly patterns exhibit substantial regional and seasonal variability.
Stefano Ubbiali, Christian Kühnlein, Christoph Schär, Linda Schlemmer, Thomas C. Schulthess, Michael Staneker, and Heini Wernli
Geosci. Model Dev., 18, 529–546, https://doi.org/10.5194/gmd-18-529-2025, https://doi.org/10.5194/gmd-18-529-2025, 2025
Short summary
Short summary
We explore a high-level programming model for porting numerical weather prediction (NWP) model codes to graphics processing units (GPUs). We present a Python rewrite with the domain-specific library GT4Py (GridTools for Python) of two renowned cloud microphysics schemes and the associated tangent-linear and adjoint algorithms. We find excellent portability, competitive GPU performance, robust execution on diverse computing architectures, and enhanced code maintainability and user productivity.
Stephanie Mayer, Martin Hendrick, Adrien Michel, Bettina Richter, Jürg Schweizer, Heini Wernli, and Alec van Herwijnen
The Cryosphere, 18, 5495–5517, https://doi.org/10.5194/tc-18-5495-2024, https://doi.org/10.5194/tc-18-5495-2024, 2024
Short summary
Short summary
Understanding the impact of climate change on snow avalanche activity is crucial for safeguarding lives and infrastructure. Here, we project changes in avalanche activity in the Swiss Alps throughout the 21st century. Our findings reveal elevation-dependent patterns of change, indicating a decrease in dry-snow avalanches alongside an increase in wet-snow avalanches at elevations above the current treeline. These results underscore the necessity to revisit measures for avalanche risk mitigation.
Heini Wernli and Suzanne L. Gray
Weather Clim. Dynam., 5, 1299–1408, https://doi.org/10.5194/wcd-5-1299-2024, https://doi.org/10.5194/wcd-5-1299-2024, 2024
Short summary
Short summary
The science of extratropical dynamics has reached a new level where the interplay of dry dynamics with effects of latent heating in clouds and other diabatic processes is considered central to the field. This review documents how research about the role of diabatic processes evolved over more than a century; it highlights that progress relied essentially on the integration of theory, field campaigns, novel diagnostics, and numerical modelling, and it outlines avenues for future research.
Ellina Agayar, Franziska Aemisegger, Moshe Armon, Alexander Scherrmann, and Heini Wernli
Nat. Hazards Earth Syst. Sci., 24, 2441–2459, https://doi.org/10.5194/nhess-24-2441-2024, https://doi.org/10.5194/nhess-24-2441-2024, 2024
Short summary
Short summary
This study presents the results of a climatological investigation of extreme precipitation events (EPEs) in Ukraine for the period 1979–2019. During all seasons EPEs are associated with pronounced upper-level potential vorticity (PV) anomalies. In addition, we find distinct seasonal and regional differences in moisture sources. Several extreme precipitation cases demonstrate the importance of these processes, complemented by a detailed synoptic analysis.
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
Short summary
Short summary
Warm conveyor belts (WCBs) are coherently ascending air streams that occur in extratropical cyclones where they form precipitation and often affect the large-scale flow. We quantified the key characteristics and impacts of WCBs and linked them to different phases in the cyclone life cycle and to different WCB branches. A climatology of these metrics revealed that WCBs are most intense during cyclone intensification and that the cyclonic and anticyclonic WCB branches show distinct differences.
Alexander Scherrmann, Heini Wernli, and Emmanouil Flaounas
Weather Clim. Dynam., 5, 419–438, https://doi.org/10.5194/wcd-5-419-2024, https://doi.org/10.5194/wcd-5-419-2024, 2024
Short summary
Short summary
We show that the formation of Mediterranean cyclones follows the presence of cyclones over the North Atlantic. The distinct regions of cyclone activity in the Mediterranean in the different seasons can be linked to the atmospheric state, in particular the position of the polar jet over the North Atlantic. With this we now better understand the processes that lead to the formation of Mediterranean cyclones. We used a novel simulation framework in which we directly show and probe this connection.
Esther S. Breuninger, Julie Tolu, Iris Thurnherr, Franziska Aemisegger, Aryeh Feinberg, Sylvain Bouchet, Jeroen E. Sonke, Véronique Pont, Heini Wernli, and Lenny H. E. Winkel
Atmos. Chem. Phys., 24, 2491–2510, https://doi.org/10.5194/acp-24-2491-2024, https://doi.org/10.5194/acp-24-2491-2024, 2024
Short summary
Short summary
Atmospheric deposition is an important source of selenium (Se) and other health-relevant trace elements in surface environments. We found that the variability in elemental concentrations in atmospheric deposition reflects not only changes in emission sources but also weather conditions during atmospheric removal. Depending on the sources and if Se is derived more locally or from further away, the Se forms can be different, affecting the bioavailability of Se atmospherically supplied to soils.
Julian F. Quinting, Christian M. Grams, Edmund Kar-Man Chang, Stephan Pfahl, and Heini Wernli
Weather Clim. Dynam., 5, 65–85, https://doi.org/10.5194/wcd-5-65-2024, https://doi.org/10.5194/wcd-5-65-2024, 2024
Short summary
Short summary
Research in the last few decades has revealed that rapidly ascending airstreams in extratropical cyclones have an important effect on the evolution of downstream weather and predictability. In this study, we show that the occurrence of these airstreams over the North Pacific is modulated by tropical convection. Depending on the modulation, known atmospheric circulation patterns evolve quite differently, which may affect extended-range predictions in the Atlantic–European region.
Leonie Villiger, Marina Dütsch, Sandrine Bony, Marie Lothon, Stephan Pfahl, Heini Wernli, Pierre-Etienne Brilouet, Patrick Chazette, Pierre Coutris, Julien Delanoë, Cyrille Flamant, Alfons Schwarzenboeck, Martin Werner, and Franziska Aemisegger
Atmos. Chem. Phys., 23, 14643–14672, https://doi.org/10.5194/acp-23-14643-2023, https://doi.org/10.5194/acp-23-14643-2023, 2023
Short summary
Short summary
This study evaluates three numerical simulations performed with an isotope-enabled weather forecast model and investigates the coupling between shallow trade-wind cumulus clouds and atmospheric circulations on different scales. We show that the simulations reproduce key characteristics of shallow trade-wind clouds as observed during the field experiment EUREC4A and that the spatial distribution of stable-water-vapour isotopes is shaped by the overturning circulation associated with these clouds.
Elena De La Torre Castro, Tina Jurkat-Witschas, Armin Afchine, Volker Grewe, Valerian Hahn, Simon Kirschler, Martina Krämer, Johannes Lucke, Nicole Spelten, Heini Wernli, Martin Zöger, and Christiane Voigt
Atmos. Chem. Phys., 23, 13167–13189, https://doi.org/10.5194/acp-23-13167-2023, https://doi.org/10.5194/acp-23-13167-2023, 2023
Short summary
Short summary
In this study, we show the differences in the microphysical properties between high-latitude (HL) cirrus and mid-latitude (ML) cirrus over the Arctic, North Atlantic, and central Europe during summer. The in situ measurements are combined with backward trajectories to investigate the influence of the region on cloud formation. We show that HL cirrus are characterized by a lower concentration of larger ice crystals when compared to ML cirrus.
Mark J. Rodwell and Heini Wernli
Weather Clim. Dynam., 4, 591–615, https://doi.org/10.5194/wcd-4-591-2023, https://doi.org/10.5194/wcd-4-591-2023, 2023
Short summary
Short summary
Midlatitude storms and their downstream impacts have a major impact on society, yet their prediction is especially prone to uncertainty. While this can never be fully eliminated, we find that the initial rate of growth of uncertainty varies for a range of forecast models. Examination of the model of the European Centre for Medium-Range Weather Forecasts (ECMWF) suggests ways in which uncertainty growth could be reduced, leading to sharper and more reliable forecasts over the first few days.
Mauro Hermann, Matthias Röthlisberger, Arthur Gessler, Andreas Rigling, Cornelius Senf, Thomas Wohlgemuth, and Heini Wernli
Biogeosciences, 20, 1155–1180, https://doi.org/10.5194/bg-20-1155-2023, https://doi.org/10.5194/bg-20-1155-2023, 2023
Short summary
Short summary
This study examines the multi-annual meteorological history of low-forest-greenness events in Europe's temperate and Mediterranean biome in 2002–2022. We systematically identify anomalies in temperature, precipitation, and weather systems as event precursors, with noteworthy differences between the two biomes. We also quantify the impact of the most extensive event in 2022 (37 % coverage), underlining the importance of understanding the forest–meteorology interaction in a changing climate.
Alexander Scherrmann, Heini Wernli, and Emmanouil Flaounas
Weather Clim. Dynam., 4, 157–173, https://doi.org/10.5194/wcd-4-157-2023, https://doi.org/10.5194/wcd-4-157-2023, 2023
Short summary
Short summary
We investigate the dynamical origin of the lower-atmospheric potential vorticity (PV; linked to the intensity of cyclones) in Mediterranean cyclones. We quantify the contribution of the cyclone and the environment by tracing PV backward in time and space and linking it to the track of the cyclone. We find that the lower-tropospheric PV is produced shortly before the cyclone's stage of highest intensity. We investigate the driving processes and use a global dataset and a process-resolving one.
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
Short summary
Short summary
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
Short summary
Short summary
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
Short summary
Short summary
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.
Andries Jan de Vries, Franziska Aemisegger, Stephan Pfahl, and Heini Wernli
Atmos. Chem. Phys., 22, 8863–8895, https://doi.org/10.5194/acp-22-8863-2022, https://doi.org/10.5194/acp-22-8863-2022, 2022
Short summary
Short summary
The Earth's water cycle contains the common H2O molecule but also the less abundant, heavier HDO. We use their different physical properties to study tropical ice clouds in model simulations of the West African monsoon. Isotope signals reveal different processes through which ice clouds form and decay in deep-convective and widespread cirrus. Previously observed variations in upper-tropospheric vapour isotopes are explained by microphysical processes in convective updraughts and downdraughts.
Philipp Zschenderlein and Heini Wernli
Weather Clim. Dynam., 3, 391–411, https://doi.org/10.5194/wcd-3-391-2022, https://doi.org/10.5194/wcd-3-391-2022, 2022
Short summary
Short summary
Precipitation and temperature are two of the most important variables describing our weather and climate. The relationship between these variables has been studied extensively; however, the role of specific weather systems in shaping this relationship has not been analysed yet. We therefore analyse whether intense precipitation occurs on warmer or on colder days and identify the relevant weather systems. In general, weather systems strongly influence this relationship, especially in winter.
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
Short summary
Short summary
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.
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
Short summary
Short summary
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.
Katharina Hartmuth, Maxi Boettcher, Heini Wernli, and Lukas Papritz
Weather Clim. Dynam., 3, 89–111, https://doi.org/10.5194/wcd-3-89-2022, https://doi.org/10.5194/wcd-3-89-2022, 2022
Short summary
Short summary
In this study, we introduce a novel method to objectively define and identify extreme Arctic seasons based on different surface variables. We find that such seasons are resulting from various combinations of unusual seasonal conditions. The occurrence or absence of different atmospheric processes strongly affects the character of extreme Arctic seasons. Further, changes in sea ice and sea surface temperature can strongly influence the formation of such a season in distinct regions.
Leonie Villiger, Heini Wernli, Maxi Boettcher, Martin Hagen, and Franziska Aemisegger
Weather Clim. Dynam., 3, 59–88, https://doi.org/10.5194/wcd-3-59-2022, https://doi.org/10.5194/wcd-3-59-2022, 2022
Short summary
Short summary
The coupling between the large-scale atmospheric circulation and the clouds in the trade-wind region is complex and not yet fully understood. In this study, the formation pathway of two anomalous cloud layers over Barbados during the field campaign EUREC4A is described. The two case studies highlight the influence of remote weather systems on the local environmental conditions in Barbados.
Philipp Zschenderlein and Heini Wernli
Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2021-396, https://doi.org/10.5194/nhess-2021-396, 2022
Preprint withdrawn
Short summary
Short summary
In early January 2021, Spain was affected by two extreme events – an unusually long cold spell and a heavy snowfall event associated with extratropical cyclone Filomena. In the study, we analyse the synoptic-dynamic development of the two extreme events. Cold air from the north was advected towards Spain and between 07 and 10 January, cyclone Filomena was responsible for major parts of the snowfall event. During this event, temperature and moisture contrasts accross Spain were very high.
Fabienne Dahinden, Franziska Aemisegger, Heini Wernli, Matthias Schneider, Christopher J. Diekmann, Benjamin Ertl, Peter Knippertz, Martin Werner, and Stephan Pfahl
Atmos. Chem. Phys., 21, 16319–16347, https://doi.org/10.5194/acp-21-16319-2021, https://doi.org/10.5194/acp-21-16319-2021, 2021
Short summary
Short summary
We use high-resolution numerical isotope modelling and Lagrangian backward trajectories to identify moisture transport pathways and governing physical and dynamical processes that affect the free-tropospheric humidity and isotopic variability over the eastern subtropical North Atlantic. Furthermore, we conduct a thorough isotope modelling validation with aircraft and remote-sensing observations of water vapour isotopes.
Gabriel Vollenweider, Elisa Spreitzer, and Sebastian Schemm
Weather Clim. Dynam. Discuss., https://doi.org/10.5194/wcd-2021-31, https://doi.org/10.5194/wcd-2021-31, 2021
Publication in WCD not foreseen
Short summary
Short summary
The interactions between the dry and moist components of the atmosphere and the influence of, for example, the phase transition of water on the atmospheric circulation are often studied from the potential vorticity (PV) framework. Changes in the PV due to, for example, condensation can relate to changes in the static stability or vorticity. To better the interaction between these two drivers of PV changes, we explore the usefulness of a novel vorticity-and-stability diagram.
Raphael Portmann, Michael Sprenger, and Heini Wernli
Weather Clim. Dynam., 2, 507–534, https://doi.org/10.5194/wcd-2-507-2021, https://doi.org/10.5194/wcd-2-507-2021, 2021
Short summary
Short summary
We explore the three-dimensional life cycle of cyclonic structures
(so-called PV cutoffs) near the tropopause. PV cutoffs are frequent weather systems in the extratropics that lead to high-impact weather. However, many unknowns exist regarding their evolution. We present a new method to track PV cutoffs as 3D objects in reanalysis data by following air parcels along the flow. We study the climatological life cycles of PV cutoffs in detail and propose a classification into three types.
Iris Thurnherr, Katharina Hartmuth, Lukas Jansing, Josué Gehring, Maxi Boettcher, Irina Gorodetskaya, Martin Werner, Heini Wernli, and Franziska Aemisegger
Weather Clim. Dynam., 2, 331–357, https://doi.org/10.5194/wcd-2-331-2021, https://doi.org/10.5194/wcd-2-331-2021, 2021
Short summary
Short summary
Extratropical cyclones are important for the transport of moisture from low to high latitudes. In this study, we investigate how the isotopic composition of water vapour is affected by horizontal temperature advection associated with extratropical cyclones using measurements and modelling. It is shown that air–sea moisture fluxes induced by this horizontal temperature advection lead to the strong variability observed in the isotopic composition of water vapour in the marine boundary layer.
Maxi Boettcher, Andreas Schäfler, Michael Sprenger, Harald Sodemann, Stefan Kaufmann, Christiane Voigt, Hans Schlager, Donato Summa, Paolo Di Girolamo, Daniele Nerini, Urs Germann, and Heini Wernli
Atmos. Chem. Phys., 21, 5477–5498, https://doi.org/10.5194/acp-21-5477-2021, https://doi.org/10.5194/acp-21-5477-2021, 2021
Short summary
Short summary
Warm conveyor belts (WCBs) are important airstreams in extratropical cyclones, often leading to the formation of intense precipitation. We present a case study that involves aircraft, lidar and radar observations of water and clouds in a WCB ascending from western Europe across the Alps towards the Baltic Sea during the field campaigns HyMeX and T-NAWDEX-Falcon in October 2012. A probabilistic trajectory measure and an airborne tracer experiment were used to confirm the long pathway of the WCB.
Franziska Aemisegger, Raphaela Vogel, Pascal Graf, Fabienne Dahinden, Leonie Villiger, Friedhelm Jansen, Sandrine Bony, Bjorn Stevens, and Heini Wernli
Weather Clim. Dynam., 2, 281–309, https://doi.org/10.5194/wcd-2-281-2021, https://doi.org/10.5194/wcd-2-281-2021, 2021
Short summary
Short summary
The interaction of clouds in the trade wind region with the atmospheric flow is complex and at the heart of uncertainties associated with climate projections. In this study, a natural tracer of atmospheric circulation is used to establish a link between air originating from dry regions of the midlatitudes and the occurrence of specific cloud patterns. Two pathways involving transport within midlatitude weather systems are identified, by which air is brought into the trades within 5–10 d.
Annika Oertel, Michael Sprenger, Hanna Joos, Maxi Boettcher, Heike Konow, Martin Hagen, and Heini Wernli
Weather Clim. Dynam., 2, 89–110, https://doi.org/10.5194/wcd-2-89-2021, https://doi.org/10.5194/wcd-2-89-2021, 2021
Short summary
Short summary
Convection embedded in the stratiform cloud band of strongly ascending airstreams in extratropical cyclones (so-called warm conveyor belts) can influence not only surface precipitation but also the
upper-tropospheric potential vorticity (PV) and waveguide. The comparison of intense vs. moderate embedded convection shows that its strength alone is not a reliable measure for upper-tropospheric PV modification. Instead, characteristics of the ambient flow co-determine its dynamical significance.
Emmanouil Flaounas, Matthias Röthlisberger, Maxi Boettcher, Michael Sprenger, and Heini Wernli
Weather Clim. Dynam., 2, 71–88, https://doi.org/10.5194/wcd-2-71-2021, https://doi.org/10.5194/wcd-2-71-2021, 2021
Short summary
Short summary
In this study we identify the wettest seasons globally and address their meteorological characteristics. We show that in different regions the wettest seasons occur in different times of the year and result from either unusually high frequencies of wet days and/or daily extremes. These high frequencies can be largely attributed to four specific weather systems, especially cyclones. Our analysis uses a thoroughly explained, novel methodology that could also be applied to climate models.
Sebastian Schemm, Heini Wernli, and Hanin Binder
Weather Clim. Dynam., 2, 55–69, https://doi.org/10.5194/wcd-2-55-2021, https://doi.org/10.5194/wcd-2-55-2021, 2021
Short summary
Short summary
North Pacific cyclone intensities are reduced in winter, which is in contrast to North Atlantic cyclones and unexpected from the high available growth potential in winter. We investigate this intensity suppression from a cyclone life-cycle perspective and show that in winter Kuroshio cyclones propagate away from the region where they can grow more quickly, East China Sea cyclones are not relevant before spring, and Kamchatka cyclones grow in a region of reduced growth potential.
Stefan Rüdisühli, Michael Sprenger, David Leutwyler, Christoph Schär, and Heini Wernli
Weather Clim. Dynam., 1, 675–699, https://doi.org/10.5194/wcd-1-675-2020, https://doi.org/10.5194/wcd-1-675-2020, 2020
Short summary
Short summary
Most precipitation over Europe is linked to low-pressure systems, cold fronts, warm fronts, or high-pressure systems. Based on a massive computer simulation able to resolve thunderstorms, we quantify in detail how much precipitation these weather systems produced during 2000–2008. We find distinct seasonal and regional differences, such as fronts precipitating a lot in fall and winter over the North Atlantic but high-pressure systems mostly in summer over the continent by way of thunderstorms.
Raphael Portmann, Juan Jesús González-Alemán, Michael Sprenger, and Heini Wernli
Weather Clim. Dynam., 1, 597–615, https://doi.org/10.5194/wcd-1-597-2020, https://doi.org/10.5194/wcd-1-597-2020, 2020
Short summary
Short summary
In September 2018 an intense Mediterranean cyclone with structural similarities to a hurricane, a so-called medicane, caused severe damage in Greece. Its development was uncertain, even just a few days in advance. The reason for this was uncertainties in the jet stream over the North Atlantic 3 d prior to cyclogenesis that propagated into the Mediterranean. They led to an uncertain position of the upper-level disturbance and, as a result, of the position and thermal structure of the cyclone.
Hanin Binder, Maxi Boettcher, Hanna Joos, Michael Sprenger, and Heini Wernli
Weather Clim. Dynam., 1, 577–595, https://doi.org/10.5194/wcd-1-577-2020, https://doi.org/10.5194/wcd-1-577-2020, 2020
Short summary
Short summary
Warm conveyor belts (WCBs) are important cloud- and
precipitation-producing airstreams in extratropical cyclones. By combining satellite observations with model data from a new reanalysis dataset, this study provides detailed observational insight into the vertical cloud structure of WCBs. We find that the reanalyses essentially capture the observed cloud pattern, but the observations reveal mesoscale structures not resolved by the temporally and spatially much coarser-resolution model data.
Cited articles
Adamson, D., Belcher, S. E., Hoskins, B. J., and Plant, R. S.: Boundary-layer
friction in midlatitude cyclones, Q. J. Roy. Meteorol. Soc., 132, 101–124,
https://doi.org/10.1256/qj.04.145, 2006. a, b, c, d
Aebischer, U. and Schär, C.: Low-level potential vorticity and cyclogenesis to the lee of the Alps, J. Atmos. Sci., 55, 186–207,
https://doi.org/10.1175/1520-0469(1998)055<0186:LLPVAC>2.0.CO;2, 1998. a
Attinger, R.: Quantifying the diabatic modification of potential vorticity in
extratropical cyclones, PhD thesis, ETH Zurich, Zurich,
https://doi.org/10.3929/ethz-b-000432253, 2020. a, b
Attinger, R., Spreitzer, E., Boettcher, M., Forbes, R., Wernli, H., and Joos,
H.: Quantifying the role of individual diabatic processes for the formation
of PV anomalies in a North Pacific cyclone, Q. J. Roy. Meteorol. Soc., 145,
2454–2476, https://doi.org/10.1002/qj.3573, 2019. a, b, c, d, e, f, g, h, i
Beare, R. J.: Boundary layer mechanisms in extratropical cyclones, Q. J. Roy.
Meteorol. Soc., 133, 503–515, https://doi.org/10.1002/qj.30, 2007. a
Binder, H., Boettcher, M., Joos, H., and Wernli, H.: The role of warm conveyor belts for the intensification of extratropical cyclones in Northern
Hemisphere winter, J. Atmos. Sci., 73, 3997–4020, https://doi.org/10.1175/JAS-D-15-0302.1, 2016. a
Boutle, I., Belcher, S. E., and Plant, R.: Friction in mid-latitude cyclones:
an Ekman-PV mechanism, Atmos. Sci. Lett., 16, 103–109, https://doi.org/10.1002/asl2.526, 2015. a
Browning, K. A.: Organization of Clouds and Precipitation in Extratropical
Cyclones, in: Extratropical Cyclones: The Erik Palmén Memorial Volume,
edited by: Newton, C. and Holopainen, E., Amer. Meteor. Soc., Boston, MA, 129–153, https://doi.org/10.1007/978-1-944970-33-8_8, 1990. a
Chagnon, J., Gray, S., and Methven, J.: Diabatic processes modifying potential vorticity in a North Atlantic cyclone, Q. J. Roy. Meteorol. Soc., 139, 1270–1282, https://doi.org/10.1002/qj.2037, 2013. a, b, c
Davis, C. A.: A potential-vorticity diagnosis of the importance of initial
structure and condensational heating in observed extratropical cyclogenesis, Mon. Weather Rev., 120, 2409–2428,
https://doi.org/10.1175/1520-0493(1992)120<2409:APVDOT>2.0.CO;2, 1992. a
Davis, C. A. and Emanuel, K. A.: Potential vorticity diagnostics of
cyclogenesis, Mon. Weather Rev., 119, 1929–1953,
https://doi.org/10.1175/1520-0493(1991)119<1929:PVDOC>2.0.CO;2, 1991. a
Dearden, C., Vaughan, G., Tsai, T., and Chen, J.-P.: Exploring the diabatic
role of ice microphysical processes in two North Atlantic summer cyclones, Mon. Weather Rev., 144, 1249–1272, https://doi.org/10.1175/MWR-D-15-0253.1, 2016. a, b
Fink, A. H., Pohle, S., Pinto, J. G., and Knippertz, P.: Diagnosing the
influence of diabatic processes on the explosive deepening of extratropical
cyclones, Geophys. Res. Lett., 39, L07803, https://doi.org/10.1029/2012GL051025, 2012. a
Flaounas, E., Gray, S. L., and Teubler, F.: A process-based anatomy of
Mediterranean cyclones: from baroclinic lows to tropical-like systems,
Weather Clim. Dynam., 2, 255–279, https://doi.org/10.5194/wcd-2-255-2021, 2021. a
Forbes, R. M. and Clark, P. A.: Sensitivity of extratropical cyclone mesoscale structure to the parametrization of ice microphysical processes, Q. J. Roy. Meteorol. Soc., 129, 1123–1148, https://doi.org/10.1256/qj.01.171, 2003. a
Hardy, S., Schultz, D. M., and Vaughan, G.: Early evolution of the 23–26 September 2012 UK floods: Tropical Storm Nadine and diabatic heating due to cloud microphysics, Mon. Weather Rev., 145, 543–563,
https://doi.org/10.1175/MWR-D-16-0200.1, 2017. a
Haualand, K. F. and Spengler, T.: Direct and Indirect Effects of Surface Fluxes on Moist Baroclinic Development in an Idealized Framework, J. Atmos. Sci., 77, 3211–3225, https://doi.org/10.1175/JAS-D-19-0328.1, 2020. a
Hoskins, B. J., McIntyre, M., and Robertson, A. W.: On the use and significance of isentropic potential vorticity maps, Q. J. Roy. Meteorol. Soc., 111, 877–946, https://doi.org/10.1002/qj.49711147002, 1985. a
Huang, H.-C. and Emanuel, K. A.: The effects of evaporation on frontal
circulations, J. Atmos. Sci., 48, 619–628,
https://doi.org/10.1175/1520-0469(1991)048<0619:TEOEOF>2.0.CO;2, 1991. a
Igel, A. L. and v. d. Heever, S. C.: The role of latent heating in warm
frontogenesis, Q. J. Roy. Meteorol. Soc., 140, 139–150, https://doi.org/10.1002/qj.2118, 2014. a
Joos, H. and Forbes, R.: Impact of different IFS microphysics on a warm
conveyor belt and the downstream flow evolution, Q. J. Roy. Meteorol. Soc.,
142, 2727–2739, https://doi.org/10.1002/qj.2863, 2016. a
Kuo, Y. H., Shapiro, M., and Donall, E. G.: The interaction between baroclinic and diabatic processes in a numerical simulation of a rapidly intensifying extratropical marine cyclone, Mon. Weather Rev., 119, 368–384,
https://doi.org/10.1175/1520-0493(1991)119<0368:TIBBAD>2.0.CO;2, 1991. a, b
Lackmann, G. M.: Cold-frontal potential vorticity maxima, the low-level jet,
and moisture transport in extratropical cyclones, Mon. Weather Rev., 130,
59–74, https://doi.org/10.1175/1520-0493(2002)130<0059:CFPVMT>2.0.CO;2, 2002. a
Lackmann, G. M. and Yablonsky, R. M.: The importance of the precipitation mass sink in tropical cyclones and other heavily precipitating systems, J. Atmos. Sci., 61, 1674–1692, https://doi.org/10.1175/1520-0469(2004)061<1674:TIOTPM>2.0.CO;2, 2004. a
Manabe, S.: On the contribution of heat released by condensation to the change in pressure pattern, J. Meteorol. Soc. Jpn., 34, 308–320,
https://doi.org/10.2151/jmsj1923.34.6_308, 1956. a
Martínez-Alvarado, O. and Plant, R.: Parametrized diabatic processes in
numerical simulations of an extratropical cyclone, Q. J. Roy. Meteorol. Soc.,
140, 1742–1755, https://doi.org/10.1002/qj.2254, 2014. a
Muir, L. C. and Reeder, M. J.: Idealized modelling of landfalling cold fronts, Q. J. Roy. Meteorol. Soc., 136, 2147–2161, https://doi.org/10.1002/qj.692, 2010. a
Neiman, P. J. and Shapiro, M.: The life cycle of an extratropical marine
cyclone. Part I: Frontal-cyclone evolution and thermodynamic air-sea
interaction, Mon. Weather Rev., 121, 2153–2176,
https://doi.org/10.1175/1520-0493(1993)121<2153:TLCOAE>2.0.CO;2, 1993. a
Neiman, P. J., Shapiro, M., Donall, E. G., and Kreitzberg, C. W.: Diabatic
modification of an extratropical marine cyclone warm sector by cold underlying water, Mon. Weather Rev., 118, 1576–1590,
https://doi.org/10.1175/1520-0493(1990)118<1576:DMOAEM>2.0.CO;2, 1990. a, b
Oertel, A. and Schemm, S.: Quantifying the circulation induced by convective
clouds in kilometer-scale simulations, Q. J. Roy. Meteorol. Soc., 147,
1752–1766, https://doi.org/10.1002/qj.3992, 2021. a
Parfitt, R., Czaja, A., and Seo, H.: A simple diagnostic for the detection of
atmospheric fronts, Geophys. Res. Lett., 44, 4351–4358, https://doi.org/10.1002/2017GL073662, 2017. a
Plant, R. and Belcher, S.: Numerical simulation of baroclinic waves with a
parameterized boundary layer, J. Atmos. Sci., 64, 4383–4399,
https://doi.org/10.1175/2007JAS2269.1, 2007. a, b
Rodwell, M. J., Magnusson, L., Bauer, P., Bechtold, P., Bonavita, M., Cardinali, C., Diamantakis, M., Earnshaw, P., Garcia-Mendez, A., Isaksen, L., Källén, E., Klocke, D., Lopez, P., McNally, T., Persson, A., Prates, F., and Wedi, N.: Characteristics of occasional poor medium-range weather forecasts for Europe, B. Am. Meteorol. Soc., 94, 1393–1405, https://doi.org/10.1175/BAMS-D-12-00099.1, 2013. a
Rossby, C.: Relation between variations in the intensity of the zonal circulation of the atmosphere and the displacements of the semi-permanent centers of action, J. Mar. Res., 2, 38–55, https://doi.org/10.1357/002224039806649023, 1939. a
Saffin, L., Methven, J., and Gray, S.: The non-conservation of potential
vorticity by a dynamical core compared with the effects of parametrized
physical processes, Q. J. Roy. Meteorol. Soc., 142, 1265–1275,
https://doi.org/10.1002/qj.2729, 2016. a
Sanders, F. and Gyakum, J. R.: Synoptic-dynamic climatology of the “bomb”,
Mon. Weather Rev., 108, 1589–1606,
https://doi.org/10.1175/1520-0493(1980)108<1589:SDCOT>2.0.CO;2, 1980. a, b
Sprenger, M. and Wernli, H.: The LAGRANTO Lagrangian analysis tool – version 2.0, Geosci. Model Dev., 8, 2569–2586, https://doi.org/10.5194/gmd-8-2569-2015, 2015. a
Stoelinga, M. T.: A potential vorticity-based study of the role of diabatic
heating and friction in a numerically simulated baroclinic cyclone, Mon.
Weather Rev., 124, 849–874, https://doi.org/10.1175/1520-0493(1996)124<0849:APVBSO>2.0.CO;2, 1996. a, b, c
Szeto, K. and Stewart, R.: Effects of melting on frontogenesis, J. Atmos. Sci., 54, 689–702, https://doi.org/10.1175/1520-0469(1997)054<0689:EOMOF>2.0.CO;2, 1997. a
Tory, K. J. and Reeder, M. J.: The effect of the continental boundary layer on the dynamics of fronts in a 2D model of baroclinic instability. I: An
insulated lower surface, Q. J. Roy. Meteorol. Soc., 131, 2389–2408,
https://doi.org/10.1256/qj.04.26, 2005. a
Valdes, P. J. and Hoskins, B. J.: Baroclinic instability of the zonally
averaged flow with boundary layer damping, J. Atmos. Sci., 45, 1584–1593,
https://doi.org/10.1175/1520-0469(1988)045<1584:BIOTZA>2.0.CO;2, 1988. a
Vannière, B., Czaja, A., Dacre, H., Woollings, T., and Parfitt, R.: A
potential vorticity signature for the cold sector of winter extratropical
cyclones, Q. J. Roy. Meteorol. Soc., 142, 432–442, https://doi.org/10.1002/qj.2662,
2016. a, b, c
Vaughan, G., Methven, J., Anderson, D., Antonescu, B., Baker, L., Baker, T. P., Ballard, S. P., Bower, K. N., Brown, P. R. A., Chagnon, J., Choularton, T. W., Chylik, J., Connolly, P. J., Cook, P. A., Cotton, R. J., Crosier, J., Dearden, C., Dorsey, J. R., Frame, T. H. A., Gallagher, M. W., Goodliff, M., Gray, S. L., Harvey, B. J., Knippertz, P., Lean, H. W., Li, D., Lloyd, G., Martínez-Alvarado, O., Nicol, J., Norris, J., Öström, E., Owen, J., Parker, D. J., Plant, R. S., Renfrew, I. A., Roberts, N. M., Rosenberg, P., Rudd, A. C., Schultz, D. M., Taylor, J. P., Trzeciak, T., Tubbs, R., Vance, A. K., van Leeuwen, P. J., Wellpott, A., and Woolley, A.: Cloud banding and winds in intense European cyclones: Results from the DIAMET project, B. Am. Meteorol. Soc., 96, 249–265, https://doi.org/10.1175/BAMS-D-13-00238.1, 2015. a
Wernli, H. and Davies, H. C.: A Lagrangian-based analysis of extratropical
cyclones. I: The method and some applications, Q. J. Roy. Meteorol. Soc., 123, 467–489, https://doi.org/10.1002/qj.49712353811, 1997.
a, b
Wernli, H. and Schwierz, C.: Surface cyclones in the ERA-40 dataset (1958–2001). Part I: Novel identification method and global climatology, J. Atmos. Sci., 63, 2486–2507, https://doi.org/10.1175/JAS3766.1, 2006. a
Willison, J., Robinson, W. A., and Lackmann, G. M.: The importance of resolving mesoscale latent heating in the North Atlantic storm track, J. Atmos. Sci., 70, 2234–2250, https://doi.org/10.1175/JAS-D-12-0226.1, 2013. a
Short summary
Diabatic processes affect the development of extratropical cyclones. This work provides a systematic assessment of the diabatic processes that modify potential vorticity (PV) in model simulations. PV is primarily produced by condensation and convection. Given favorable environmental conditions, long-wave radiative cooling and turbulence become the primary process at the cold and warm fronts, respectively. Turbulence and long-wave radiative heating produce negative PV anomalies at the fronts.
Diabatic processes affect the development of extratropical cyclones. This work provides a...
