Drivers of Tropical Circulation

Close to the equator, the deep tropics are the home of extensive cloud systems and towering clouds with heavy precipitation. In the neighboring subtropics vast areas of cloud-free sky or shallow puffy clouds prevail. The two areas do not only differ in their visual appearance but also in their atmospheric structures, e.g. in terms of temperature and humidity profiles. Another difference is how they contribute to the tropical heat budget, i.e. the balance of incoming and outgoing energy fluxes. Yet the deep tropics and the subtropics are not two separate systems but they live on different branches of a common circulation that connects both regions. Our group aims to better understand how both regions contribute to the overall tropical heat budget, how they link through the circulation system, and how sensitive the system is to perturbations. Understanding of these processes will help to anticipate how the circulation and the associated precipitation patterns in this key region will respond to warming.

Our group focuses on process understanding and the interplay between the tropical circulation and its different drivers of heat exchange (diabatic drivers). These include radiation, cloud microphysics (cloud processes such as droplet growth, evaporation, etc. taking place on the scale of individual water drops or ice particles that form clouds), and surface heat fluxes. All of these drivers fundamentally act on very small scales. While some of the underlying processes are relatively well understood, limitations in our understanding of other processes might blur the big picture. Our group therefore tries to better understand how much of the heat budget of the tropics is controlled by circulations and dynamics as compared to by these small-scale diabatic drivers.

Climate scientists have applied numerical models of the atmosphere for decades. But only recently kilometer-scale global storm-resolving climate models became feasible. The possibility to study the climate system with these storm-resolving models presents exciting opportunities and new science challenges. Storm-resolving models apply grid meshes that are fine enough to resolve the vertical parts of the circulation which directly couples microphysical processes to the circulation – something that conventional climate models were not able to do. Building on the combination of storm-resolving modelling with observations and conceptual approaches, we ask: to what extent do microphysical processes influence the energy budget of the tropics, and its sensitivity to perturbations? Even at grid scales of a few hundred meters microphysical processes itself will be crudely represented, raising the question as to whether it matters, and if it matters to what extent they can be constrained by observations.

The CLICCS joint working group on Drivers of Tropical Circulation is funded through the cluster of excellence CLICCS, and is run as a joint working group of the Max Planck Institute for Meteorology and the Universität Hamburg.

Group webpage at the Meteorological Institute of the Universität Hamburg

Group members and publications

Phd Candidate
B 424
  • Fons, E., Naumann, A., Neubauer, D., Lang, T. & Lohmann, U. (2024). Investigating the sign of stratocumulus adjustments to aerosols in the global storm-resolving model ICON. Under open review for Atmospheric Chemistry and Physics. Atmospheric Chemistry and Physics. doi:10.5194/egusphere-2024-195 [Preprint]
  • Hohenegger, C., Korn, P., Linardakis, L., Redler, R., Schnur, R., Adamidis, P., Bao, J., Bastin, S., Behravesh, M., Bergemann, M., Biercamp, J., Bockelmann, H., Brokopf, R., Brüggemann, N., Casaroli, L., Chegini, F., Datseris, G., Esch, M., George, G., Giorgetta, M., Gutjahr, O., Haak, H., Hanke, M., Ilyina, T., Jahns, T., Jungclaus, J., Kern, M., Klocke, D., Kluft, L., Kölling, T., Kornblueh, L., Kosukhin, S., Kroll, C., Lee, J., Mauritsen, T., Mehlmann, C., Mieslinger, T., Naumann, A., Paccini, L., Peinado, A., Praturi, D., Putrasahan, D., Rast, S., Riddick, T., Roeber, N., Schmidt, H., Schulzweida, U., Schütte, F., Segura, H., Shevchenko, R., Singh, V., Specht, M., Stephan, C., von Storch, J., Vogel, R., Wengel, C., Winkler, M., Ziemen, F., Marotzke, J. & Stevens, B. (2023). ICON-Sapphire: simulating the components of the Earth System and their interactions at kilometer and subkilometer scales. Geoscientific Model Development, 16, 779-811. doi:10.5194/gmd-16-779-2023 [publisher-version]
  • Lang, T., Naumann, A., Buehler, S., Stevens, B., Schmidt, H. & Aemisegger, F. (2023). Sources of uncertainty in mid-tropospheric tropical humidity in global storm-resolving simulations. Journal of Advances in Modeling Earth Systems, 15: e2022MS003443. doi:10.1029/2022MS003443 [publisher-version]
  • Lang, T. (2023). On the uncertainty in modelling tropical relative humidity. Phd Thesis, Hamburg: Universität Hamburg. Berichte zur Erdsystemforschung, 263. doi:10.17617/2.3501977 [publisher-version]
  • Radtke, J., Vogel, R., Ament, F. & Naumann, A. (2023). Spatial organisation affects the pathway to precipitation in simulated trade-wind convection. Geophysical Research Letters, 50: e2023GL103579. doi:10.1029/2023GL103579 [publisher-version]
  • Radtke, J., Naumann, A., Hagen, M. & Ament, F. (2022). The relationship between precipitation and its spatial pattern in the trades observed during EUREC(4)A. Quarterly Journal of the Royal Meteorological Society, 148, 1913-1928. doi:10.1002/qj.4284
  • Shi, L., Schreck III, C., John, V., Chung, E.-S., Lang, T., Buehler, S. & Soden, B. (2022). Assessing the consistency of satellite-derived upper tropospheric humidity measurements. Atmospheric Measurement Techniques, 15, 6949-6963. doi:10.5194/amt-15-6949-2022 [publisher-version]
  • George, G., Stevens, B., Bony, S., Pincus, R., Fairall, C., Schulz, H., Kölling, T., Kalen, Q., Klingebiel, M., Konow, H., Lundry, A., Prange, M. & Radtke, J. (2021). JOANNE: Joint dropsonde Observations of the Atmosphere in tropical North atlaNtic mesoscale Environments. Earth System Science Data, 13, 5253-5272. doi:10.5194/essd-13-5253-2021 [publisher-version]
  • Konow, H., Ewald, F., George, G., Jacob, M., Klingebiel, M., Kölling, T., Luebke, A., Mieslinger, T., Pörtge, V., Radtke, J., Schäfer, M., Schulz, H., Vogel, R., Wirth, M., Bony, S., Crewell, S., Ehrlich, A., Forster, L., Giez, A., Gödde, F., Groß, S., Gutleben, M., Hagen, M., Hirsch, L., Jansen, F., Lang, T., Mayer, B., Mech, M., Prange, M., Schnitt, S., Vial, J., Walbröl, A., Wendisch, M., Wolf, K., Zinner, T., Zöger, M., Ament , F. & Stevens, B. (2021). EUREC4A's HALO. Earth System Science Data, 13, 5545-5563. doi:10.5194/essd-13-5545-2021 [publisher-version][supplementary-material]
  • Lang, T., Naumann, A., Stevens, B. & Buehler, S. (2021). Tropical free-tropospheric humidity differences and their effect on the clear-sky radiation budget in global strom-resolving models. Journal of Advances in Modeling Earth Systems, 13: e2021MS002514. doi:10.1029/2021MS002514 [publisher-version]
  • Stevens, B., Bony, S., Farrell, D., Ament, F., Blyth, A., Fairall, C., Karstensen, J., Quinn, P., Speich, S., Acquistapace, C., Aemisegger, F., Albright, A., Bellenger, H., Bodenschatz, E., Caesar, K.-A., Chewitt-Lucas, R., de Boer, G., Delanoë, J., Denby, L., Ewald, F., Fildier, B., Forde, M., George, G., Gross, S., Hagen, M., Hausold, A., Heywood, K., Hirsch, L., Jacob, M., Jansen, F., Kinne, S., Klocke, D., Kölling, T., Konow, H., Lothon, M., Mohr, W., Naumann, A., Nuijens, L., Olivier, L., Pincus, R., Pöhlker, M., Reverdin, G., Roberts, G., Schnitt, S., Schulz, H., Siebesma, A., Stephan, C., Sullivan, P., Touzé-Peiffer, L., Vial, J., Vogel, R., Zuidema, P., Alexander, N., Alves, L., Arixi, S., Asmath, H., Bagheri, G., Baier , K., Bailey, A., Baranowski, D., Baron, A., Barrau, S., Barrett, P., Batier, F., Behrendt, A., Bendinger, A., Beucher, F., Bigorre, S., Blades, E., Blossey, P., Bock, O., Böing, S., Bosser, P., Bourras, D., Bouruet-Aubertot, P., Bower, K., Branellec, P., Branger, H., Brennek, M., Brewer, A., Brilouet, P.-E., Brügmann, B., Buehler, S., Burke, E., Burton, R., Calmer, R., Canonici, J.-C., Carton, X., Cato, G., Charles, J., Chazette, P., Chen, Y., Chilinski, M., Choularton, T., Chuang, P., Clarke, S., Coe, H., Cornet, C., Coutris, P., Couvreux, F., Crewell, S., Cronin, T., Cui, Z., Cuypers, Y., Daley, A., Damerell, G., Dauhut, T., Deneke, H., Desbios, J.-P., Dörner, S., Donner, S., Douet, V., Drushka, K., Dütsch, M., Ehrlich, A., Emanuel, K., Emmanouilidis, A., Etienne, J.-C., Etienne-Leblanc, S., Faure, G., Feingold, G., Ferrero, L., Fix, A., Flamant, C., Flatau, P., Foltz, G., Forster, L., Furtuna, I., Gadian, A., Galewsky, J., Gallagher, M., Gallimore, P., Gaston, C., Gentemann, C., Geyskens, N., Giez, A., Gollop, J., Gouirand, I., Gourbeyre, C., de Graaf, D., de Groot, G., Grosz, R., Güttler, J., Gutleben, M., Hall, K., Harris, G., Helfer, K., Henze, D., Herbert, C., Holanda, B., Ibanez-Landeta, A., Intrieri, J., Iyer, S., Julien, F., Kalesse, H., Kazil, J., Kellman, A., Kidane, A., Kirchner, U., Klingebiel, M., Körner, M., Kremper, L., Kretzschmar, J., Krüger, O., Kumala, W., Kurz, A., L'Hégaret, P., Labaste, M., Lachlan-Cope, T., Laing, A., Landschützer, P., Lang, T., Lange, D., Lange, I., Laplace, C., Lavik, G., Laxenaire, R., Le Bihan, C., Leandro, M., Lefevre, N., Lena, M., Lenschow, D., Li, Q., Lloyd, G., Los, S., Losi, N., Lovell, O., Luneau, C., Makuch, P., Malinowski, S., Manta, G., Marinou, E., Marsden, N., Masson, S., Maury, N., Mayer, B., Mayers-Als, M., Mazel, C., McGeary, W., McWilliams, J., Mech, M., Mehlmann, M., Meroni, A., Mieslinger, T., Minikin, A., Minnett, P., Möller, G., Morfa Avalos, Y., Muller, C., Musat, I., Napoli, A., Neuberger, A., Noisel, C., Noone, D., Nordsiek, F., Nowak, J., Oswald, L., Parker, D., Peck, C., Person, R., Philippi, M., Plueddemann, A., Pöhlker, C., Pörtge, V., Pöschl, U., Pologne, L., Posyniak, M., Prange, M., Meléndez, E., Radtke, J., Ramage, K., Reimann, J., Renault, L., Reus, K., Reyes, A., Ribbe, J., Ringel, M., Ritschel, M., Rocha, C., Rochetin, N., Röttenbacher, J., Rollo, C., Royer, H., Sadoulet, P., Saffin, L., Sandiford, S., Sandu, I., Schäfer, M., Schemann, V., Schirmacher, I., Schlenczek, O., Schmidt, J., Schröder, M., Schwarzenboeck, A., Sealy, A., Senff, C., Serikov, I., Shohan, S., Siddle, E., Smirnov, A., Späth, F., Spooner, B., Stolla, M., Szkółka, W., de Szoeke, S., Tarot, S., Tetoni, E., Thompson, E., Thomson, J., Tomassini, L., Totems, J., Ubele, A., Villiger, L., von Arx, J., Wagner, T., Walther, A., Webber, B., Wendisch, M., Whitehall, S., Wiltshire, A., Wing, A., Wirth, M., Wiskandt, J., Wolf, K., Worbes, L., Wright, E., Wulfmeyer, V., Young, S., Zhang, C., Zhang, D., Ziemen, F., Zinner, T. & Zöger, M. (2021). EUREC4A. Earth System Science Data, 13, 4067-4119. doi:10.5194/essd-13-4067-2021 [publisher-version]
  • Fiedler, S., Crueger, T., D'Agostino, R., Peters, K., Becker, T., Leutwyler, D., Paccini, L., Burdanowitz, J., Buehler, S., Uribe, A., Dauhut, T., Dommenget, D., Fraedrich, K., Jungandreas, L., Maher, N., Naumann, A., Rugenstein, M., Sakradzija, M., Schmidt, H., Sielmann, F., Stephan, C., Timmreck, C., Zhu , X. & Stevens, B. (2020). Simulated tropical precipitation assessed across three major phases of the Coupled Model Intercomparison Project (CMIP). Monthly Weather Review, 148, 3653-3680. doi:10.1175/MWR-D-19-0404.1 [publisher-version][supplementary-material]
  • Naumann, A. & Kiemle, C. (2020). The vertical structure and spatial variability of lower tropospheric water vapor and clouds in the trades. Atmospheric Chemistry and Physics, 20, 6129-6145. doi:10.5194/acp-20-6129-2020 [publisher-version]
  • Stevens, B., Acquistapace, C., Hansen, A., Heinze, R., Klinger, C., Klocke, D., Schubotz, W., Windmiller, J., Adamidis, P., Arka, I., Barlakas, V., Biercamp, J., Brueck, M., Brune, S., Buehler, S., Burkhardt, U., Cioni, G., Costa-Surós, M., Crewell, S., Crueger, T., Deneke, H., Friederichs, P., Henken, C., Hohenegger, C., Jacob, M., Jakub, F., Kalthoff, N., Köhler, M., van Laar, T., Li, P., Lohnert, U., Macke, A., Madenach, N., Mayer, B., Nam, C., Naumann, A., Peters, K., Poll, S., Quaas, J., Röber, N., Rochetin, N., Rybka, H., Scheck, L., Schemann, V., Schnitt, S., Seifert, A., Senf, F., Shapkalijevski, M., Simmer, C., Singh, S., Sourdeval, O., Spickermann, D., Strandgren, J., Tessiot, O., Vercauteren, N., Vial, J., Voigt, A. & Zängl, G. (2020). The added value of large-eddy and storm-resolving models for simulating clouds and precipitation. Journal of the Meteorological Society of Japan, 98, 395-435. doi:10.2151/jmsj.2020-021 [publisher-version]
  • Stevens, B., Bony, S., Brogniez, H., Hentgen, L., Hohenegger, C., Kiemle, C., L'Ecuyer, T., Naumann, A., Schulz, H., Siebesma, P., Vial , J., Winker, D. & Zuidema, P. (2020). Sugar, gravel, fish, and flowers: Mesoscale cloud patterns in the tradewinds. Quarterly Journal of the Royal Meteorological Society, 146, 141-152. doi:10.1002/qj.3662 [publisher-version][supplementary-material]
  • Klingebiel, M., Ghate, V., Naumann, A., Ditas, F., Pöhlker, M., Pöhlker, C., Kandler, K., Konow, H. & Stevens, B. (2019). Remote sensing of sea salt aerosol below trade wind clouds. Journal of the Atmospheric Sciences, 76, 1189-1202. doi:10.1175/JAS-D-18-0139.1 [publisher-version]
  • Naumann, A., Stevens, B. & Hohenegger, C. (2019). A moist conceptual model for the boundary layer structure and radiatively driven shallow circulations in the trades. Journal of the Atmospheric Sciences, 76, 1289-1306. doi:10.1175/JAS-D-18-0226.1 [supplementary-material][publisher-version]
  • Vial, J., Vogel , R., Bony, S., Stevens, B., Winker, D., Cai, X., Hohenegger, C., Naumann, A. & Brogniez, H. (2019). A new look at the daily cycle of trade wind cumuli. Journal of Advances in Modeling Earth Systems, 11, 3148-3166. doi:10.1029/2019MS001746 [supplementary-material][publisher-version]


Dr. Ann Kristin Naumann

Group leader
Phone: +49 (0)40 41173-424
ann-kristin.naumann@we dont want

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