Working Group: Atmosphere, Ice and Ocean


Ha Hagemann

Wikis 🔑 AIO

Overall Objective

The main general aim is to improve the representation of the regional ocean and its interaction with the atmosphere in the COSMO-CLM and ICON-CLM.

State of the art, scientific developments

Regional climate models (RCMs) are tools for dynamical downscaling coarse results from global climate circulation models (GCMs), which are nowadays mainly coupled atmosphere-ocean models (AOGCMs). Ideally, RCMs should be able to determine the regional climate without the influence of the GCMs, except at the lateral boundaries. However, presently this is not the case for COSMO-CLM/ICON-CLM, since the lower boundary values over the sea are taken from the AOGCMs. This has a major impact on the quality of the regional model simulations as shown already for the Baltic Sea, the North Sea and the Mediterranean Sea. To overcome this problem regional coupled atmosphere-ocean models may be used for climate simulations. Several groups in the CLM-Community are working on the coupling of a regional ocean to COSMO-CLM/ICON-CLM.

Objectives of participating groups

  • Improve the representation of the ocean and the interaction with the atmosphere in the COSMO-CLM (Goethe University Frankfurt, BiK-F)

  • Better regional representation of the North Sea and Baltic Sea in climate simulations in the COSMO-CLM and ICON-CLM (Hereon, DWD)

  • Simulating polynya processes in the Laptev Sea and the Weddell Sea with a fully coupled A-I-O model (University Trier)

  • Assess the added value of high-resolution climatic hindcasts and scenarios for the Mediterranean when using coupled atmosphere-ocean models (IMK-TRO (KIT))

  • To get better accuracy, since in the CIRA simulations the lower boundary values over the sea are taken from the global coupled model CMCC-MED. A better regional representation of the Mediterranean Sea is also important in order to increase the accuracy also for climate simulations of the Alpine space (CIRA)

  • Carry out simulations over the Southern Ocean to investigate seasonal simulations covering the confluence region of the Brazil and Malvinas currents, where many oceanic eddies occur (C2SM-ETHZ). Thereby two major questions are addressed:
    - What is the impact of the highly resolved SST on fluxes between the atmosphere and the ocean and on the lower troposphere? Are highly resolved SSTs required to realistically represent fluxes of heat and freshwater in that region?
    - How are these processes affected by the coupling between the atmosphere and the ocean?


The red boxes give a rough idea of the domains, however, they do not represent the exact boundaries.

Models: Ocean / Ice / Runoff / Wave






Mediterranean Sea, North Sea, Baltic Sea

Jennifer Brauch, Bodo Ahrens, Trang van Pham, Naveed Akhtar


no update available

NEMO / (SI3)

North Sea, Baltic Sea

Vera Maurer




North Sea, Baltic Sea

Ha Hagemann, Burkhardt Rockel




North Sea, Baltic Sea

Ha Hagemann, Burkhardt Rockel


development stopped


North Sea, Baltic Sea

Anne Wiese




Arctic, Laptev Sea, Svalbard

Oliver Gutjahr


no update available

NEMO?/ (LIM) /

(Western) Mediterranean, Northeast Atlantic

Hendrik Feldmann, Gerd Schädler, Hans-Jürgen Panitz


no update available

NEMO / (LIM) /

Mediterranean Sea

Andreas Will

BTU Cottbus

no update available

NEMO / (LIM) /

Mediterranean Sea

Leone Cavicchia, Antonella Sanna, Silvio Gualdi and Paolo Oddo


no update available

ROMS / /

Southern Atlantic

David Byrne, Lukas Papritz


no update available


Baltic Sea

Markus Meier, Hagen Radtke, Sven Karsten



Ocean model /

Pavel Khain



Ocean model /

CORDEX East Asia

Donghyun Lee

Pohang University of Science and Technology, South Korea




Meeting and Location



CLM-Assembly Online Meeting


CLM-Assembly Online Meeting

🔑 Minutes


ICCARUS online

🔑 Minutes


CLM-Assembly Online Meeting

🔑 Minutes


CLM-Assembly in Karlsruhe

🔑 Minutes


ICCARUS in Offenbach

🔑 Minutes


CLM-Assembly in Graz

🔑 Minutes


ICCARUS in Offenbach

🔑 Minutes


CLM-Assembly in Lüneburg

🔑 Minutes


CLM-Community Assembly in Zürich


COSMO/CLM Seminar in Offenbach


CLM-Community Assembly in Leuven

🔑 Minutes


COSMO/CLM Seminar in Offenbach


CLM-Community Assembly in Cava de' Tirreni


COSMO/CLM Seminar in Langen


Startup Meeting in Berlin


2018 🔑 Annual WG Presentation at Assembly

2017🔑 Annual WG Presentation at Assembly

2011/08/26 Annual report 2011

2012/09/13   Annual report 2012

2013/09/17   Annual report 2013 


Akhtar, N., J. Brauch, B. Ahrens (2017): Climate Modeling over the Mediterranean Sea: Impact of Resolution and Ocean Coupling. Clim. Dyn. DOI 10.1007/s00382-017-3570-8

Akhtar, N.J., J. Brauch, A. Dobler, K. Béranger, B. Ahrens (2014): Medicanes in an ocean-atmosphere coupled regional climate model. Nat. Hazards Earth Syst. Sci., 14, 2189-2201, doi:10.5194/nhess-14-2189-2014

Byrne, D., M. Münnich, I. Frenger, N. Gruber (2016): Mesoscale atmosphere-ocean coupling enhances the transfer of wind energy into the ocean, Nature Communications 7, doi:10.1038/ncomms11867

Gröger, M., Dieterich, C., Haapala, J., Ho-Hagemann, H.T.M., Hagemann, S., Jakacki, J., May, W., Meier, H.E.M., Miller, P.A., Rutgersson, A., & Wu, L. (2021): Coupled regional Earth system modeling in the Baltic Sea region. Earth Syst. Dynam., 12, 939–973, doi:10.5194/esd-12-939-2021

Hagemann, Stefan, & Ho-Hagemann, Ha T.M. (2021). The Hydrological Discharge Model - a river runoff component for offline and coupled model applications (5.1.0). Zenodo.

Ho-Hagemann, H.T.M. (2022). The OASIS3-MCT Coupling Interface for ICON-CLM (1.0.0). Zenodo.

Ho-Hagemann, H.T.M., Hagemann, S., Grayek, S., Petrik, R., Rockel, B., Staneva, J., Feser, F., & Schrum, C. (2020): Internal Model Variability of the Regional Coupled System Model GCOAST-AHOI. Atmosphere 2020, 11, 227, doi:10.3390/atmos11030227

Ho-Hagemann, H.T.M., & Rockel, B. (2018): Einfluss von Atmosphäre-Ozean Wechselwirkungen auf Starkniederschläge über Europa. In: Lozán, J.L., Breckle, S.-W., Graßl, H., Kasang, D., & Weisse, R. (Hsg.): Warnsignal Klima: Extremereignisse,

Ho-Hagemann, H., Gröger, M., Rockel, B., Zahn, M., Geyer, B., Meier, M., 2017: Effects of air-sea coupling over the North Sea and the Baltic Sea on simulated summer precipitation over Central Europe, Climate Dynamics, pp 1–26, doi:10.1007/s00382-017-3546-8.

Ho-Hagemann, H.T.M., S. Hagemann, B. Rockel (2015): On the role of soil moisture in the generation of heavy rainfall during the Oder flood event in July 1997. Tellus A, 67, 28661. DOI:10.3402/tellusa.v67.28661.

Ho-Hagemann H, Rockel B, Kapitza H and Geyer B (2013): COSTRICE-an atmosphere-ocean-sea ice model coupled system using OASIS3, HZG Report (2013-5), 24pp

Pham, Trang Van; J. Brauch, B. Früh, B. Ahrens (2017): Simulation of snowbands in the Baltic Sea area with the coupled atmosphere-ocean-ice model COSMO-CLM/NEMO. Met. Z., doi: 10.1127/metz/2016/0775

Pham, T.V., J. Brauch, C. Dieterich, B. Früh, B. Ahrens (2014): New coupled atmosphere-ocean-ice system COSMO-CLM/NEMO: On the air temperature sensitivity on the North and Baltic Seas. Oceanologia, 56(2), 167-189, doi:10.5697/oc.56-2.167

Rockel, B., J. Brauch, O. Gutjahr, N. Akhtar, H.T.M. Ho-Hagemann (2017): Gekoppelte Modellsysteme: Atmosphäre und Ozean. Promet - Meteorologische Fortbildung, 99, 65-75

Rockel, B. (2022). SPICE (Starter Package for ICON-CLM Experiments) (1.1). Zenodo.

Ruti P.M., S. Somot, F. Giorgi, C. Dubois, E. Flaounas, A. Obermann, A. Dell'Aquila, G. Pisacane, A. Harzallah, E. Lombardi, B. Ahrens, N. Akhtar, A. Alias, T. Arsouze, R. Aznar, S. Bastin, J. Bartholy, K. Béranger, J. Beuvier, S. Bouffies-Cloché, J. Brauch, W. Cabos, S. Calmanti, J.-C. Calvet, A. Carillo D. Conte, E. Coppola, V. Djurdjevic, P. Drobinski, A. Elizalde-Arellano, M. Gaertner, P. Galàn, C. Gallardo, S. Gualdi, M. Goncalves, O. Jorba, G. Jordà, B. L'Heveder, C. Lebeaupin-Brossier, L. Li, G. Liguori, P. Lionello, D. Maciàs-Moy, P. Nabat, B. Onol, B. Rajkovic, K. Ramage, F. Sevault, G. Sannino, M.V. Struglia, A. Sanna, C. Torma, V. Vervatis (2016): MED-CORDEX initiative for Mediterranean Climate studies. Bull. of the American Meteorological Society, 97(7), 1187-1208, doi: 10.1175/BAMS-D-14-00176.1

Wahle, K.; Staneva, J.; Koch, W.; Fenoglio-Marc, L.; Ho-Hagemann, H.T.M.; Stanev, E.V.: An atmosphere-wave regional coupled model: improving predictions of wave heights and surface winds in the southern North Sea. In: Ocean Science. Vol. 13 (2017) 2, 289 - 301. (DOI: 10.5194/os-13-289-2017)

Wiese, A., Staneva, J., Ho-Hagemann, H.T.M., Grayek, S., Koch, W., & Schrum, C. (2020): Internal Model Variability of Ensemble Simulations With a Regional Coupled Wave-Atmosphere Model GCOAST. Front. Mar. Sci. 7:596843, doi:10.3389/fmars.2020.596843

Will, A., N. Akhtar, J. Brauch, M. Breil, E. Davin, H. T. M. Ho-Hagemann, E. Maisonnave, M. Thürkow, and S. Weiher (2017): The COSMO-CLM 4.8 regional climate model coupled to regional ocean, land surface and global earth system models using OASIS3-MCT: description and performance. Geoscientific Model Development, 10:1549–1586, doi:10.5194/gmd-10-1549-2017


List of WG AIO members 🔑

Bodo Ahrens, Naveed Akhtar, Jennifer Brauch, Alberto Elizalde, Imoleayo Ezekiel Gbode, Ha Hagemann, Mostafa Hamouda, Shabeh Ul Hasson, Günther Heinemann, Samuel Helsen, Ines Hoeschel, Sven Karsten, Astrid Kerkweg, Moritz Kirschner, Svenja Kohnemann, Melissa Körlin, Donghyun Lee, Yunfei Li, Tania Liartsi, Xiao Luo, Sylvain Marchi, Vera Maurer, Sofia Papadogiannaki, Lukas Papritz, Charles Pelletier, Trang Van Pham, Cristina Primo Ramos, Hagen Radtke, Burkhardt Rockel, Harald Sodemann, Het Thakkar, Nele Tim, Alexandra Touzeau, Anne Wiese, Andreas Will, Rolf Zentek

Mailing List

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Coordinator Alumni List

Jennifer Brauch (2016 - 2021)

Bodo Ahrens (2014 - 2016)

Burkhardt Rockel (2010 - 2014)

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