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
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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
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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
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Mauro Hermann, Matthias Röthlisberger, Arthur Gessler, Andreas Rigling, Cornelius Senf, Thomas Wohlgemuth, and Heini Wernli
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Alexander Scherrmann, Heini Wernli, and Emmanouil Flaounas
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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
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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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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.
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
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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
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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
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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.
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.
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
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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
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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
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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
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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
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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
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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
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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
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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.
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...
