L4: Energy-Consistent Ocean-Atmosphere Coupling

Principal investigators: Dr. Nils Brüggemann (Max Planck Institute for Meteorology), Dr. Cathy Hohenegger (Max Planck Institute for Meteorology), Dr. Stephan Juricke (Constructor University), Dr. Lars Umlauf (Leibniz Institute for Baltic Sea Research Warnemünde)

Figure 1

Recent studies highlight the importance of small-scale coherent structures associated with atmospheric convection and (sub-)mesoscale ocean dynamics on atmosphere-ocean feedbacks in key regions of the climate system. In state-of-the-art coupled climate models, such small-scale atmosphere-ocean feedbacks are either ignored or rely on parameterizations, which may lead to model biases and energetic inconsistencies. In this subproject, we investigate these small-scale coupling mechanisms using coupled simulations on a global scale, based on resolutions allowing us, for the first time, to directly simulate the underlying key processes. More specifically, we focus on the following topics:

(i) With the help of storm-resolving coupled simulations and data from a large-scale field experiment conducted in the tropical Atlantic, we investigate the interaction of shallow atmospheric convection and near-surface processes in the ocean. A special focus here is on the dynamics of thin (meter-scale) "diurnal warm layers" and "rain layers" at the ocean surface, their role in mediating air-sea fluxes, and their feedback with atmospheric convection (see figure 1).

Figure 2

(ii) We also study the effect of parameterized submesoscale dynamics like baroclinic instability and symmetric instability on atmosphere-ocean coupling (see figure 2). To this end, the role of submesoscale dynamics on atmosphere-ocean feedbacks in selected key regions of the climate system is investigated with the help of coupled global simulations at unprecedented resolution (see figure 3). These simulations are also used to develop and test parameterizations of these effects in more coarsely resolved global ocean-atmosphere models. Our final goal is to obtain an integral estimate of the role of submesoscale dynamics on the coupling between the atmosphere and the ocean.

(iii) Finally, we aim to clarify the effect of resolved mesoscale eddies on air-sea coupling (see figure 2), develop a new stochastic parameterization that represents such effects in surface fluxes of heat and momentum, and investigate the global and regional impact of the parameterization in coupled atmosphere-ocean simulations that cannot use high enough resolution to represent those processes explicitly.

Figure 3

Research Stay in Perth by Mira Schmitt (Oct 23)

At the end of last year, I spent two months in Perth, Western Australia, to work on a collaborative project with Jen-Ping Peng, who was a PhD in TRR181’s first phase and is now a PostDoc in the working group of Nicole Jones at the Indian Ocean Marine Research Centre of the University of Western Australia. For the most part, my stay in Perth was covered by the Australia–Germany Joint Research Cooperation Scheme, with the TRR kindly providing some additional financial support. The above scheme is an initiative of Universities Australia and the German Academic Exchange Service (DAAD) for the support of international academic cooperation. Early-career researchers from Australia and Germany are encouraged to hand in proposals for a joint research topic, and, if approved, the grant covers the expenses for a research stay at the partner institute. For our project, Jen-Ping and I decided that we want to combine our two fields of research and investigate the interactions of diurnal warm layers, submesoscale fronts and other turbulent processes in the surface mixed layer. For this, we firstly extended the 1D turbulence model GOTM to include 3D frontal effects and validated our model results by comparing them to published LES studies. Then, we used our model to recreate measurements taken previously during two campaigns in the Baltic Sea and the Indian Ocean and use the results to understand the governing processes involved. We found nice agreements between the measurements and our simple model and are planning on publishing two joint papers on these topics.

But besides the work aspect, Western Australia was also a great place to explore and spend time. Jen-Ping was an excellent host (I think we went to every great Asian restaurant in all of Perth) and the weather was pleasant from beginning to end (basically nothing but sunshine for two months). I stayed in a researcher accommodation on campus, which is located a few kilometres away from the city centre directly at the Swan river estuary with lots of green areas and beautiful old trees. Moreover, I got to go on two nice road trips up and down the coast, explore the Margaret River wine region, see quokkas on Rottnest Island and snorkel in the beautiful Ningaloo Reeve national reserve with an infinite amount of fish, stingrays and even a big sea turtle. I also got to see a living colony of stromatolites, microorganisms that are believed to be the oldest form of life on earth dating back 3 billion years, and that can only survive in hypersaline estuaries like Shark Bay in Western Australia. And while there were a few snake and spider sightings, I didn’t have the heart to look up their level of toxicity, so I like to believe it was all safe and sound.

I can definitely recommend looking into the Joint Research Cooperation Scheme (it exists not only between Germany and Australia, but also other countries) and would strongly encourage others to take the opportunity to extend their network and travel, maybe to Perth, it’s a lovely corner of the world. I would like to thank Jen-Ping, Nicole Jones and all other members of this working group for hosting me, showing interest in my research and teaching me about their fields of research.

Diurnal Warm Layers and Rain Layers: Dynamics, Turbulence and Atmospheric Feedbacks

My work so far has been to simulate idealized cases using a 1D turbulence model.

Mira Schmitt, PhD L4

Hello everyone, my name is Mira, I am a PhD at the Institute for Baltic Sea Research in Warnemünde and working in subproject L4, supervized by Lars Umlauf. To start off with something about myself: I studied physics at the University of Göttingen with a focus on Astro- and Geophysics during my masters. After an internship on sea ice physics at the University of Otago in New Zealand, I studied double-diffusive convection during my master thesis.

I love hiking and backpacking, so before, during and after my studies I spent a lot of time abroad, travelling, discovering new countries and meeting interesting people. When the pandemic started I had to change my plans and, by a chain of coincidences, started this phd position, which I am very happy about. I very much enjoy to live this close to the ocean and I spend a lot of time by the beach.

The focus of my project is on diurnal warm layers and rain layers on the ocean surface. These thin, stratified layers influence air-sea fluxes and turbulence in the ocean interior, but are usually not resolved in climate models. My work so far has been to simulate idealized cases using a 1D turbulence model. With that I can identify the non-dimensional parameters that govern these processes and perform parameter space studies, which can be the basis for a parameterization. I also work in close collaboration with Mira Shevchenko and Cathy Hohenegger, who study diurnal warm layers and their effect on the atmosphere using the coupled ICON model.

  • Schmitt, M., Pham, H.T., Sarkar, S., Klingbeil, K. & Umlauf, L. (2024). Diurnal warm layers in the ocean: energetics, non-dimensional scaling, and parameterization. J. Phys. Oceanogr. 54(4), 1037–1055, doi: https://doi.org/10.1175/JPO-D-23-0129.1.

  • Shevchenko, R., Hohenegger, C., & Schmitt, M. (2023). Impact of diurnal warm layers on atmospheric convection. J. Geophys. Res. - Atmospheres 128(14), e2022JD038473, doi: https://doi.org/10.1029/2022JD038473

  • Umlauf, L., Klingbeil K., Radke, H., Schwefel, R., Bruggeman, J. & Holtermann, P.L. (2023). Hydrodynamic control of sediment-water fluxes: Consistent parameterization and impact in coupled benthic-pelagic models. J. Geophys. Res. - Oceans 128, e2023JC019651, doi: https://doi.org/10.1029/2023JC019651

  • Shi, J., Stepanek, C., Sein, D., Streffing, J., & Lohmann, G. (2023). East Asian summer precipitation in AWI-CM3: Comparison with observations and CMIP6 models. International Journal of Climatology, 1– 16, doi: https://doi.org/10.1002/joc.8075

  • Pithan, F., Athanase, M., Dahlke, S., Sánchez-Benítez, A., Shupe, M. D., Sledd, A., Streffing, J., Svensson, G., & Jung, T. (2023). Nudging allows direct evaluation of coupled climate models with in situ observations: a case study from the MOSAiC expedition. Geosci. Model Dev. 16(7), 1857–1873, doi: https://doi.org/10.5194/gmd-16-1857-2023

  • Hohenegger, C., Korn, P., Brüggemann, N., Gutjahr, O., Jungclaus, J., Shevchenko, R., von Storch, J.S. et al. (2023). ICON-Sapphire: simulating the components of the Earth system and their interactions at kilometer and subkilometer scales. Geosci. Model Dev. 16, 779–811, doi: https://doi.org/10.5194/gmd-16-779-2023.

  • Chrysagi, E., Basdurak, N.B., Umlauf, L., Gräwe, U. & Burchard, H. (2022). Thermocline Salinity Minima Due To Wind-Driven Differential Advection. J. Geophys. Res.- Oceans 127(11), doi: https://doi.org/10.1029/2022JC018904

  • Streffing, J., Scholz, P., Koldunov, N., Danilov, S., Juricke, S., Jung, T. et al. (2022). AWI-CM3 coupled climate model: description and evaluation experiments for a prototype post-CMIP6 model. Geosci. Model Dev. 15, 6399–6427, doi: https://doi.org/10.5194/gmd-15-6399-2022

  • Strommen, K., Juricke, S. & Cooper, F. (2022). Improved teleconnection between Arctic sea ice and the North Atlantic Oscillation through stochastic process representation. Weather Clim. Dynam. 3(3), 951–975, doi: https://doi.org/10.5194/wcd-3-951-2022.

  • Franzke, C.L.E., Gugole, F. & Juricke, S. (2022). Systematic multi-scale decomposition of ocean variability using machine learning. Chaos: An Interdisciplinary Journal of Nonlinear Science 32(7), 073122, doi: https://doi.org/10.1063/5.0090064

  • Kumar, A., Brüggemann, N., Smith, R., & Marotzke, J. (2022). Response of a tropical cyclone to a subsurface ocean eddy and the role of boundary layer dynamics. Q.J.R. Meteorol. Soc. 148, 378-402, doi: https://doi.org/10.1002/qj.4210

  • Peng, J.-P., Dräger-Dietel, J., North, R. P., & Umlauf, L. (2021). Diurnal Variability of Frontal Dynamics, Instability, and Turbulence in a Submesoscale Upwelling Filament, J. Phys.Oceanogr. 51(9), 2825-2843, doi: https://doi.org/10.1175/JPO-D-21-0033.1.

  • Sidorenko, D., Danilov, S., Streffing, J., Juricke, S., Jung, T., Koldunov, N. et al. (2021). AMOC variability and watermass transformations in the AWI climate model. J. Adv. Model Earth Sy. 13, e2021MS002582, doi: https://doi.org/10.1029/2021MS002582.

  • Li, Q., Bruggemann, J., Burchard, H., Klingbeil, K., Umlauf, L. & Bolding, K. (2021). Integrating CVMix into GOTM (v6.0): a consistent framework for testing, comparing, and applying ocean mixing schemes. Geosci. Model Dev., doi: https://doi.org/10.5194/gmd-14-4261-2021.

  • Carpenter, J. R. , Rodrigues, A., Schultze, L. K. P., Merckelbach, L. M., Suzuki, N., Baschek, B. & Umlauf, L. (2020). Shear Instability and Turbulence Within a Submesoscale Front Following a Storm. Geophys. Res. Lett., doi: https://doi.org/10.1029/2020GL090365.

  • Rackow, T., & Juricke, S (2019). Flow‐dependent stochastic coupling for climate models with high ocean‐to‐atmosphere resolution ratio. Q. J. Roy. Meteor. Soc., 1-17, https://doi.org/10.1002/qj.3674.