W1: Gravity Wave Parameterisation for the Atmosphere

Principal investigators: Prof. Ulrich Achatz (Goethe University Frankfurt), Dr. Gerd Baumgarten (Leibniz Institute of Atmospheric Physics), Prof. Carsten Eden (University of Hamburg)

Objectives

The goal of subproject W1 is the establishment of an energetically consistent approach to gravity-wave parameterisation (GWP) in atmosphere models. GWPs represent the key role of gravity waves (GWs) in the atmospheric energy cycle by their energetic coupling, both to the resolved flow and to turbulence. Moreover, energetically consistent GWPs help us to better understand the role of GWs in the climate system. Subproject W1 develops such GWPs of different complexity and efficiency and validates them with observations and process resolving simulations. MS-GWaM, implemented successfully in ICON-a, is the first, and so far only, GWP representing both transient GW-mean interactions and lateral GW propagation, and hence the resulting development of GW energy spectra and GW interaction with mean flow and turbulence. A conceptually simplified approach, as compared to MS-GWaM, is IDEMIX-a that has also been implemented in ICON-a. It is based on the same theory as MS-GWaM, but the GW spectrum is prescribed, thereby allowing for reduced dimensionality of the closure, less costly simulations, and easier conceptual insights. This model hierarchy represented by MS-GWaM and IDEMIX-a is a unique asset of the atmospheric GWP strategy developed in subproject W1.

The following core themes will be in focus:

MS-GWaM will be coupled to the prognostic turbulence model in ICON-a to allow for a consistent treatment of the energy budget. In parallel the description of the coupling between the resolved flow and GWs shall be further substantially enhanced by making all GW sources in MS-GWaM flow dependent.
IDEMIX-a shall be developed further following MS-GWaM’s example, by including downward and lateral GW propagation, a compartment for orographic waves, and by allowing for a more general evolution of the GW energy spectra.
Both MS-GWaM and IDEMIX-a will be validated against observational data from co-located lidar, radar, and rocket soundings in terms of WP spectra and turbulence levels using previously developed methods.

The development of energetically consistent GWPs for atmosphere models, together with the detailed validation using the new observational data, form an integral part of the CRC work on energetically consistent models.

Reports

Report - Ocean Sciences 2026 in Glasgow by Michael Cox

At the end of February, TRR181 went on tour to Ocean Sciences 2026, the first big conference of the year. Where better to talk marine science than the thriving port city of Glasgow?

Our journey started in the wee hours in Hamburg. We numbered four – Pablo, Belal, Moritz and me. As we travelled, our numbers grew, and we soon had a gaggle of oceanographers in Amsterdam. We resisted the debauchery frequently embraced by my fellow Brits in the Dutch capital, opting instead for a stroll along the canals. Our ferry left in the early evening and we arrived in Newcastle the following morning.

There were blue skies over the cliffs of North-East England as we approached land. This is the closest I have ever come to a research cruise and I was delighted to see a grey seal in the harbour. My Nature paper on the sighting will be available shortly.

At Newcastle, we boarded the train for a picturesque journey along the Northumberland coastline up to Edinburgh. Upon arrival, I introduced our quartet to the Scottish breakfast roll, with haggis, black pudding and tattie scones. Later, Belal paid £8 to kiss an owl. The weather turned as we made our way to Glasgow but despite the rain, our spirits remained high. Belal looked wistfully out of the train window, yearning for his avian companion.

The opening reception for the conference was held in the Glasgow Science Centre which contained interactive exhibitions for Pablo and the other children in attendance. The grown-up science started the following day.

Project members Manita Chouksey, Han Wang, Friederike Pollmann and Pablo Sebastia Saez together convened four sessions on internal and surface gravity waves. There were two oral sessions, a poster session and an eLightning (digital poster) session. All were well attended and the science was riveting. A resounding success! Elsewhere, Nils Brueggemann chaired oral and poster sessions on energy transfers in turbulence, and Knut Klingbeil chaired sessions on the numerical challenges in ocean model development.

The programme ran from 8.30 am to 6 pm every day. In the evenings, we sampled the finest food and drink Glasgow has to offer. For example, we ate at a curry house with a gallery of famous guests on their walls including royalty and presidents. The waiter took an unexpected photograph of us and returned with a framed copy to commemorate our visit.

Somehow, Pablo and I found time in our busy schedule to visit the University of Glasgow alongside friend-of-the-TRR Gaspard Geoffroy. The buildings would have looked quite at home in a certain popular wizardry franchise. The campus houses the Hunterian museum, with an impressive collection of scientific equipment including a tide gauge and Lord Kelvin’s harmonic analyser. As tidal researchers, Gaspard and I found this thrilling.

On Thursday evening, we headed to a party hosted by Scripps oceanographers and watched senior professors get plastered to the tune of Chappell Roan’s Pink Pony Club. Afterwards our group split. Some people went into a basement bar to watch topless men play heavy metal, whilst Yang, Belal and I went to a corner shop and purchased a pint of milk.

After the previous night’s indulgences, it was impressive that we made it to the conference for 8.30 am the following day. As the talks drew to a close, we reflected on a successful week. We all felt enthusiastic to get back to Hamburg and start working on new ideas! For Pablo, Han and I, the fun wasn’t over. We would spend the following week hosted in Edinburgh by TRR181 Mercator fellow, Jacques Vanneste.

The highlights of our second week included visits to the National Museum of Scotland, walks up Arthur’s seat and Blackford Hill, and Pablo’s sensational talk in the Waves & Flows seminar series at the University of Edinburgh. Jacques hosted us for a delicious meal on our final night together. This generous hospitality was a fitting end to our time in the UK – an enjoyable and productive trip for everyone involved.

Research Stay in Lyon by Mohamed Mossad (Oct 23)

Exploring Atmospheric Dynamics

From the 1st of October and until the 14th, I had the opportunity to embark on a short research stay in Lyon, France, funded by the project TRR181 at École Centrale de Lyon. This period was not just a chance to collaborate and learn but also a stepping stone in my understanding of atmospheric dynamics, particularly regarding gravity wave (GW) spectra.

My time in Lyon was spent working alongside Raffaele Marino (scientist at CNRS, France) and the team at the Laboratory Mechanical Des Fluides Et D'acoustique (LMFA). The environment at LMFA was not only academically stimulating but also warmly welcoming, fostering both professional growth and personal connections.

One of the most enlightening aspects of this visit was the shift in my perspective on the processes which contribute to the canonical GW spectra. Discussions about turbulence and the scaling of gravity wave spectra opened my eyes to the broader physics underlying these phenomena. It was a transition from focusing merely on the slope of gravity wave spectra to understanding the vast, open-ended field of their scaling.

A highlight of my stay was exploring the relationship between the Froude number and statistics (kurtosis) of velocity and temperature fields. Although time constraints didn’t allow for its application on lidar data, the concepts presented were inspiring and thought-provoking.

Our work concentrated on validation of spectra from direct numerical simulations (DNS) against lidar data, scrutinizing how different wind regimes affect GW spectra. This involved a detailed comparison of integrated kinetic energy/scalar spectra with lidar data.

Leaving Lyon, I am armed with an array of studies and topics to delve into, especially regarding the comparison with DNS regimes. These studies are pivotal in enhancing our interpretation of GW data from lidar measurements. I am optimistic about the continuation of this collaboration in the future and the potential for significant findings.

Beyond the academic realm, Lyon itself proved to be a delightful experience. The city's transportation system was notably efficient which made commuting a breeze. The streets of Lyon are filled with friendly faces, many of them young students, also the 2023 Rugby World Cup was taking place there which added a lively and diverse vibe to the city. École Centrale de Lyon, nestled in this vibrant environment, struck me as an exceptional place for study and research, providing many chances to do sports as well.

I extend my deepest gratitude to the entire team at LMFA for their hospitality and support. Special thanks go to Rafaello Foldes and Fabio Feraco (IAP) for their invaluable help in answering my questions and assistance with data provision.

My research stay in Lyon was not only productive but also immensely rewarding. It has broadened my understanding and has surely impacted my approach to atmospheric science. I am grateful for this experience and hopeful that my contributions, though a fraction, have added value to our collective research endeavors.

Publications

Mossad, M., Strelnikova, I., Wing, R., Baumgarten, G. & Gerding, M. (2025). Spectral variability of gravity-wave kinetic and potential energy at 69° N: a seven-year lidar study. Atmospheric Chemistry And Physics, 25(21), 14839–14864. https://doi.org/10.5194/acp-25-14839-2025
Brüggemann, N., Losch, M., Scholz, P., Pollmann, F., Danilov, S., Gutjahr, O., Jungclaus, J., Koldunov, N., Korn, P., Olbers, D., Eden, C. (2024). Parameterized Internal Wave Mixing in Three Ocean General Circulation Models. Journal of Advances in Modeling Earth Systems, 16, e2023MS003768. doi: https://doi.org/10.1029/2023MS003768
Listowski, C., Stephan, C.C., Le Pichon, A., Hauchecorne, A., Kim, Y.-H., Achatz, U. & Bölöni, G. (2024). Stratospheric gravity waves impact on infrasound transmission losses across the International Monitoring System. Pure Appl. Geophys., doi: https://doi.org/10.1007/s00024-024-03467-3.
Kim, Y.-H., Voelker, G. S., Bölöni, G., Zängl, G. & Achatz, U. (2024). Crucial role of obliquely propagating gravity waves in the quasi-biennial oscillation dynamics. Atmos. Chem. Phys. 24(5), 3297-3308, doi: https://doi.org/10.5194/acp-24-3297-2024.
Achatz, U., Alexander, M.J., Becker, E. et al. (2024). Atmospheric Gravity Waves: Processes and Parameterization. J. Atmos. Sci. 18, 237-262, doi: https://doi.org/10.1175/JAS-D-23-0210.1.
Mossad, M., Strelnikova, I., Wing, R. & Baumgarten, G. (2024). Assessing Atmospheric Gravity Wave Spectra in the Presence of Observational Gaps. Atmos. Meas. Tech. 17, 783–799, doi: https://doi.org/10.5194/amt-17-783-2024.
Achatz, U., Kim, Y.-H. & Voelker, G.S. (2023). Multi-Scale Dynamics of the Interaction Between Waves and Mean Flows: From Nonlinear WKB Theory to Gravity-Wave Parameterizations in Weather and Climate Models. J. Math. Phys. 64(11), 111101, doi: https://doi.org/10.1063/5.0165180.
Dolaptchiev, S.D., Spichtinger, P., Baumgartner, M. & Achatz, U. (2023). Interactions between gravity waves and cirrus clouds: asymptotic modeling of wave induced ice nucleation. J. Atmos. Sci. 80(12), 2861–2879, doi: https://doi.org/10.1175/JAS-D-22-0234.1.
Schaefer-Rolffs, U. (2023). A Dynamic Mixed Model for General Circulation Models. Meteorol. Z. (Contrib. Atm. Sci.), doi: https://doi.org/10.1127/metz/2023/1160.
Olbers, D., Pollmann, F., Patel, A. & Eden, C. (2023). A model of energy and spectral shape for the internal gravity wave field in the deep-sea – The parametric IDEMIX model. J. Phys.Oceanogr. 53(5), doi: https://doi.org/10.1175/JPO-D-22-0147.1.
Vadas, S. L., Becker, E., Baumgarten, G. et al. (2023). Secondary gravity waves from the stratospheric polar vortex over ALOMAR observatory on 12–14 January 2016: Observations and modeling. J. Geophys. Res. - Atmospheres 128(2), e2022JD036985, doi: https://doi.org/10.1029/2022JD036985.
Schmid, F., Gagarina, E., Klein, R. & Achatz, U. (2021). Toward a Numerical Laboratory for Investigations of Gravity Wave–Mean Flow Interactions in the Atmosphere. Mon. Wea. Rev. 149, 4005–4026, doi: https://doi.org/10.1175/MWR-D-21-0126.1.
Eden, C., Olbers, D. & Eriksen, T. (2021). A closure for lee wave drag on the large-scale ocean circulation. J. Phys. Oceanogr. 51(12), doi: https://doi.org/10.1175/JPO-D-20-0230.1.
Quinn, B., Eden, C. & Olbers, D. (2020). Application of the IDEMIX Concept for Internal Gravity Waves in the Atmosphere. J. Atmos. Sci. 77(10), 3601–3618, doi: https://doi.org/10.1175/JAS-D-20-0107.1.
Olbers, D., Jurgenowski, P., & Eden, C. (2020). A wind-driven model of the ocean surface layer with wave radiation physics. Ocean Dynam. 70, doi: https://doi.org/10.1007/s10236-020-01376-2.
Olbers, D., Eden, C., Becker, E., Pollmann, F., & Jungclaus, J. (2019). The IDEMIX Model: Parameterization of Internal Gravity Waves for Circulation Models of Ocean and Atmosphere. In Energy Transfers in Atmosphere and Ocean (pp. 87-125). Springer, Cham., doi: https://doi.org/10.1007/978-3-030-05704-6_3.
Pollmann, F., Eden, C. & Olbers, D. (2017). Evaluating the Global Internal Wave Model IDEMIX Using Finestructure Methods.Am. Met. Soc., doi: 10.1175/JPO-D-16-0204.1.
Eden, C. & Olbers, D. (2017). A closure for eddy-mean flow effects based on the Rossby wave energy equation. Ocean Model., 114, 59-71, doi: https://doi.org/10.1016/j.ocemod.2017.04.005.
Olbers, D. & Eden, C. (2017). A closure for internal wave-mean flow interaction. Part A: Energy conversion.J. Phys. Oceanogr., doi.org/10.1175/JPO-D-16-0054.1.
Eden, C. & Olbers, D. (2017). A closure for internal wave-mean flow interaction. Part B: Wave drag. J. Phys. Oceanogr., doi: https://doi.org/10.1175/JPO-D-16-0056.1.