Project B07:
Impact of cirrus clouds on tropopause structure

Brief Summary

Cirrus clouds, i.e. clouds containing exclusively of ice particles, occur quite frequently in the tropopause region. They have a crucial impact on the thermodynamic structure of the UTLS region by diabatic processes, i.e. latent heating due to phase transitions and radiative effects due to absorption and emission of radiation; actually, temperature gradients and water vapor distributions are actively changed by the formation and evolution of these clouds. On the other hand, ice clouds in the cold temperature regime in the tropopause region are crucially affected by local dynamics. Gravity waves as well as dynamic and convective instabilities may have a strong impact on the life cycle of cirrus clouds, thus affecting also indirectly the tropopause region. The main goal of this project is the investigation of the interaction of dynamical processes and ice clouds in the tropopause region and their impact on the thermodynamic structure and composition of the tropopause region. Using theoretical investigations as well as numerical modeling, we will be able to develop a consistent parameterisation of these interactions and their impacts on the tropopause region for the use in coarse grid models.

The following central questions are addressed in this project:

• What are the dominant processes of interaction between cirrus clouds and dynamics for changing tropopause properties?
• How can theory and model approaches be used for developing state-of-the-art parameterisations of tropopause ice-cloud processes in coarse resolution models?

For addressing these questions we propose a two-fold approach combining theoretical investigations and numerical model simulations. We will use sophisticated mathematical methods in order to determine dominant processes and interactions between ice clouds and dynamical processes. These methods will also be used for deriving reduced order models. Complementary, we will use numerical simulations of relevant ice cloud scenarios in the tropopause region, using a hierarchy of models. Combining these two approaches we will develop prototype parameterisations, which will be implemented into the ICON model on the basis of an existing framework, developed for gravity wave parameterisations.

Members

Publications

Achatz, U., M. J. Alexander, E. Becker, H.-Y. Chun, A. Dörnbrack, L. Holt, R. Plougonven, I. Polichtchouk, K. Sato,
A. Sheshadri, C. C. Stephan, A. van Niekerk, and C. J. Wright (2024): Atmospheric Gravity Waves: Processes and
Parameterization. Journal of the Atmospheric Sciences 81 (2), 237–262. https://doi.org/10.1175/JAS-D-23-0210.1

Achatz, U., Y.-H. Kim, and G. S. Voelker (Nov. 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. Journal
of Mathematical Physics 64 (11), 111101. doi: 10.1063/5.016518

Dolaptchiev, S. I., P. Spichtinger, M. Baumgartner, and U. Achatz (2023): Interactions between gravity waves and cirrus clouds: asymptotic modeling of wave induced ice nucleation. doi: https://doi.org/10.1175/JAS-D-22-0234.1.

C. Listowski, C. C. Stephan, A. Le Pichon, A. Hauchecorne, Y.-H. Kim, U. Achatz, and G. Bölöni, 2024: Stratospheric gravity waves impact on infrasound transmission losses across the International Monitoring System. Pure and Applied Geophysics, accepted

Spichtinger, P., P. Marschalik, and M. Baumgartner (2023): Impact of formulations of the homogeneous nucleation
rate on ice nucleation events in cirrus. Atmospheric Chemistry and Physics 23 (3), 2035–2060. doi: 10.5194/acp-
23-2035-2023