[A-AS06] Atmospheric (Stratosphere-troposphere) Processes And their Role in Climate

[AAS06-05] The development of a three-dimensional spectral mechanistic circulation model and its application to the study of atmospheric dynamics

★Invited Papers

*Keiichi Ishioka¹ (1.Graduate School of Science, Kyoto University)

Keywords:spectral method, mechanistic circulation model, atmospheric dynamics, atmospheric free oscillation

For many years, the speaker has developed and published a numerical library (ISPACK) focusing on the spherical harmonic transform, and recently, the speaker's group has proposed a formulation of a three-dimensional spectral mechanistic circulation model as an application of ISPACK. This model has a feature that, by discretising not only in the horizontal direction but also in the vertical direction using the spectral method, a highly accurate numerical solution can be obtained with fewer degrees of freedom compared to conventional models that use the finite difference method in the vertical direction. Taking advantage of this feature, the speaker's group has carried out several studies of atmospheric dynamics using or motivated by this numerical model. The first is a study of how the meridional and the vertical structure of zonal wind and temperature fields affects the eigenfrequencies of atmospheric free oscillation modes and the meridional/vertical structure. The second is a study of QBO-like zonal wind fluctuations in dry atmospheric dynamical cores and how the difference in the vertical discretisation and the different resolutions affect their occurrence. The third is a study on the estimation of the equivalent depth of Pekelis waves observed during the eruption of Hunga Tonga-Hunga Haʻapai in 2022. This presentation will briefly introduce the formulation of the proposed three-dimensional spectral mechanistic circulation model and review the main results of the above three studies.