Our group works on various aspects of atmospheric dynamics and transport related to internal gravity waves (GWs) in the atmosphere and their representation in models. Using a synergy of theory, observations, existing data mining and experiments with a a hierarchy of numerical models (spanning from idealized to GW resolving and chemistry-climate models) we want to revisit and advance our understanding of the climate impacts of GWs and improve their current parameterizations.

An animation of specific kinetic energy in the stratosphere from a regional (southern tip of Andes) high-resolution model simulation. Note the synoptic evolution of the jet overlaid with GW induced oscillations.

Current research objectives

  • Evaluation of the parameterized GW drag-resolved dynamics interaction in chemistry-climate models based on GW resolving simulations.
  • Revision of climate impact of GWs deduced from their parameterizations based on GW resolving simulations.
  • Development of GW parameterizations without artificial effects on model dynamics and transport.
A sketch illustrating the current understanding of GW climate impacts and the information source it is based on. The level of uncertainty connected with all of the aspects highlights that this is still an open question with high societal relevance.

Workshop on internal gravity waves and atmospheric dynamics

Since 2021, each Summer we organize a small GW workshop in Prague. The program and agenda from previous years can be found here (2021, 2022). Group foto (2022, roof of the faculty building)

In 2023 the workshop took place 28.8.2023-30.8.2023 in a larger format (around 20 participants), with talks by Ulrich Achatz, Christoph Jacobi, Corwin Wright, Claudia Stephan, George Sebastian Völker and many others! For more information on 2023, see the workshop website.

Group foto (2023, venue of the workshop)

We are starting to organize the 2024 GW workshop, the list of invited speakers and information about registration and abstract submission can be found here.

Tools

  • Theoretical research of internal gravity waves and wave-mean flow interaction.
  • Lagrangian (FLEXPART), idealistic (ICAR), high-resolution (WRF) and chemistry-climate models (EMAC)
  • Reanalyses (ERA 5.1) and mining of observational (AIRS, GPS RO) and model data (DYAMOND initiative, CMIP6)

Publications

Hájková, D., and Šácha, P. Parameterized orographic gravity wave drag and dynamical effects in CMIP6 models. Climate Dynamics, 2023.https://doi.org/10.1007/s00382-023-07021-0.

Procházková, Z., Kruse, C. G., Alexander, M. J., Hoffmann, L., Bacmeister, J. T., Holt, L., Wright, C., Sato, K., Gisinger, S., Ern, M., Geldenhuys, M., Preusse, P., & Šácha, P. (2023). Sensitivity of mountain wave drag estimates on separation methods and proposed improvements. Journal of the Atmospheric Sciences. https://doi.org/10.1175/JAS-D-22-0151.1.

Preprints

Fujiwara, M., Martineau, P., Wright, J. S., Abalos, M., Šácha, P., Kawatani, Y., Davis, S. M., Birner, T., and Monge-Sanz, B. M.: Climatology of the terms and variables of transformed Eulerian-mean (TEM) equations from multiple reanalyses: MERRA-2, JRA-55, ERA-Interim, and CFSR, EGUsphere [preprint], 2023. https://doi.org/10.5194/egusphere-2023-2917

Petr Šácha, Radek Zajíček, Ales Kuchar, et al. Unravelling the kinematics of the Brewer-Dobson circulation change. ESS Open Archive . August 17, 2023.
 https://doi.org/10.22541/essoar.169230312.27488559/v1

Faculty

Postdoctoral Scholars

  • Dr. Anahí Villalba Pradas – Responsible for dedicated WRF simulations and leading the research on the role of GWs in the upper troposphere – lower stratosphere region, especially for irreversible mixing in this region. See my full list of publications here.
  • Open position – full time postdoc for 3 years in climate modelling! Contact petr.sacha(at)matfyz.cuni.cz for further details or expressions of interest.

Students

  • Mgr. Zuzana Procházková – Diagnoses resolved GW effects in high-resolution simulations and analyses the GW influence on the polar stratospheric vortices in both hemispheres. See my personal website here.
  • Mgr. Radek Zajíček – Looks at the contribution of GWs to transport processes in the middle atmosphere, particulary how the wave driving of the BDC changes in GW resolving datasets.
  • MSc. Massimo Martina – Uses Lagrangian models to study the stratosphere-troposphere exchange and transport processes in mountainous terrain.
  • Bc. Dominika Hájková – Works on modifications of the traditional GW parameterization schemes and their coupling with the models to achieve a similar mechanism of interaction with resolved processes in CCMs as constrained by GW resolving datasets. See my ResearchGate profile here.
  • Open position (partly funded with a further possibility to apply for your own project in the internal Charles University grant competition) – we welcome applications from MSc or fresh doctoral students to work with us on deriving a relationship between GW parameters, background state and type of instability with the efficiency of turbulent GW induced mixing. With the goal to parameterize this process in chemistry-climate models. Contact petr.sacha(at)matfyz.cuni.cz for further details or expressions of interest.

External Collaborators

  • Prof. Ulrich Achatz (Goethe University Frankfurt)
  • Dr. Manfred Ern (Research Centre Jülich)
  • Dr. Hella Garny (DLR)
  • Dr. Christopher Kruse (NWRA)
  • Prof. Kaoru Sato (University of Tokyo)
  • Prof. Harald Rieder (BOKU Wien)
  • Dr. Corwin Wright (University of Bath)
  • Dr. Claudia Stephan (IAP)

Funding

The group is funded by the Czech Science Foundation under the Junior Star grant 23-04921M „Unravelling climate impacts of atmospheric internal gravity waves.“ awarded to Petr Šácha. Period of funding (1.1.2023-31.12.2027).