[A-AS21_30AM1] Stratospheric Processes And their Role in Climate

[AAS21-03] Tropical non-migrating tides appearing in a high vertical resolution GCM

*Takatoshi SAKAZAKI¹, Kaoru SATO², Yoshio KAWATANI³, Shingo WATANABE³ (1.Research Institute for Sustainable Humanosphere, Kyoto University, 2.Graduate School of Science, The University of Tokyo, 3.JAMSTEC)

Keywords:nonmigrating tides, KANTO, SABER, COSMIC

Atmospheric tides are global scale waves with periods that are harmonics of a solar day. They are primarily excited in the troposphere and the stratosphere, and then, propagate upward. Tides are generally classified into two components: migrating (Sun-synchronous) and non-migrating (non-Sun-synchronous) tides. Although migrating tides were examined by many previous studies, a much fewer studies considered non-migrating tides particularly in the troposphere and the stratosphere. The purpose of this study is to reveal the horizontal and vertical structure of non-migrating tides and its seasonal variations in the region from the troposphere to the mesosphere, as well as to clarify the underlying physical processes. In this study, data from a high-resolution (T213L256) global spectral climate model (Watanabe et al., 2008) are analyzed. This model covers quite a wide height range from the ground surface to the upper mesosphere (80 km in altitude), enabling us to investigate the full tidal coupling between the lower and upper atmosphere. Also, the vertical resolution is ~300 m in the vertical, which is almost sufficient to simulate realistic propagation and momentum deposition of gravity waves including tides. We compared the model data with data from COSMIC GPS-RO measurements and TIMED/SABER satellite measurements, and confirmed that the model captures the observed characteristics at least qualitatively. In the model data, we clearly see that non-migrating tides are mainly excited over the two large continents: over Africa and South America. The excited tides are propagating three-dimensionally like internal inertia-gravity waves. During the propagation, tides with small wavenumbers are filtered out by background zonal wind (e.g., stratospheric semiannual oscillation (SAO)). Thus, both excitation and filtering processes are important for understanding the tidal variability.