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

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.

A Memory of Pre-Pandemic Times and a Glimpse at the hopefully soon-to-be Future: My Visit at MIT and the AGU Fall Meeting 2021

With two successful talks, one on my research at the CRC181 and one on my science policy activities, I am more than happy with the received exposure and appreciation of our work.
Georg Sebastian Voelker, Postdoc in W1, S2

Having been in the home office for a long time during the last two years I am sure everyone wonders: Remember how things were before the virus hit? And how things will be afterwards? I was asking myself the very same questions while having a travel grant available I had won mid 2020 from the DFG research unit MS-GWaves which was still sitting in the accounts waiting to be used. My visit had been planned for a long time but had also been delayed by the pandemic. So when the US started opening up to foreign visitors in late summer 2021 I decided to try to move forward with the plan we had been setting aside for so long. And despite the restrictions and insecurities linked to long distance travel I should very soon be rewarded. On November 8 I boarded an airplane to Cambridge, Massachusetts to visit the long research partner of out group, Prof. Triantaphyllos Akylas at the Massachusetts Institute of Technology.

Our former and ongoing research project with T. R. Akylas is concerned with the background-modulated wave-wave interaction of internal gravity waves. In a previous manuscript we had been able to show that wave modulation by a sheared mean flow can significantly inhibit the energy exchange through a near-resonant triadic interaction. However, the assumptions of Boussinesq dynamics and a constant stratification limited the applicability of the findings to the atmospheric context. We thus took on the task to extend the theory to semi-incompressible dynamics with both a variable stratification and sheared mean winds. Having derived the theory beforehand we used the 5 weeks together at MIT to explore the combined effects of the modulation by the wind and the stratification on the wave interaction. Interestingly the two modulation mechanisms can counteract each other opening up the possibility of strong interactions in regions with both changing stratification and strong shear. As the tropopause region typically exhibits these features it is of particular interest to be studied. A manuscript is now in preparation and planned to be submitted later this year.

Having already traveled to the US another possibility opened for me: the in-person attendance of the fall meeting of the American Geophysical Union in New Orleans. Traveling to conferences has always been one of my favorite parts of being a scientist. I am particular fond of getting to know places and people, exchanging ideas about our research, networking among peers and like-minded people and making friends throughout the world. The idea of attending a conference on site for the first time in two years was therefore especially tempting for me. Even though it came with the huge insecurity of sharing the venue with another 10,000 people during a pandemic the stringent health policies helped keeping the participants safe and the number of infections low.

With two successful talks, one on my research at the CRC181 and one on my science policy activities, I am more than happy with the received exposure and appreciation of our work. Fostering existing connections and forging new ones additionally rendered the conference experience as a very positive one. But maybe most importantly, I also realized what I had been missing out in the past months. Even though video conferences can account for the majority of the scientific collaboration it will not be able to replace the experience of and the human relationships associated to a person to person contact. Partnerships are build on these relationships and I am hoping that there will be a time soon where we can find a way to get back together. Personally I feel motivated to move forward and make progress in ways that I had not expected when I boarded that airplane on November 8. I would therefore like to particularly thank the CRC181, the research group MS-GWaves, the WilhelmHeraeus Visiting Professorship program and not at last Prof. Ulrich Achatz and Prof. Triantaphyllos Akylas for enabling this collaboration and the conference participation for me.

Publications

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.