[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-P19] Medium-Scale Traveling Ionospheric Disturbances Created by Weather Front Gravity Waves

*Masaru Kogure^1,2,3、Min-Yang Chou^2,3、Jia Yue^3,2、Yuichi Otsuka⁴、Huixin Liu¹、Fabrizio Sassi²、Nicholas M Pedatella⁵、Cora E. Randall⁶、Lynn Harvey⁶ (1.Kyushu University、2.NASA/GSFC、3.Department of Physics, Catholic University of America、4.Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan.、5.High Altitude Observatory, National Center for Atmospheric Research, Boulder, USA、6.Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA)

キーワード：Gravity wave, Weather front, Medium-Scale Traveling Ionospheric Disturbances

This study explores the meteorological source and vertical propagation of gravity waves (GWs) that drive daytime traveling ionospheric disturbances (TIDs), using SD-WACCM-X and SAMI3 simulations driven by SD-WACCM-X neutral wind and composition. A weather front occurred over the northern-central U.S.A. with strong upward airflow during the daytime of 20th October 2020. GWs with ~500-700 km horizontal wavelengths propagated southward/northward in the thermosphere over the north-central U.S.A. Also, the perturbations were coherent from the surface to the thermosphere; therefore, the GWs were likely generated by the strong upward airflow associated with the weather front. The front-generated GWs had almost infinite vertical wavelengths below ~100 km due to being the evanescent, implying that the GWs tunneled through their turning level where a squared vertical wavenumber is equal to/smaller than 0 (below ~100 km) in the middle atmosphere and became freely propagating in the thermosphere and ionosphere. Medium-scale TIDs (MSTIDs) also propagated southward together with the GWs, suggesting that the MSTIDs were created by the frontal GWs. Comparisons between GNSS TEC observations and MSTIDs modeled by SD-WACCM-X and SAMI3 are conducted. MSTIDs with concentric structures propagated southward in the GNSS TEC observations, and their apparent epicenter was over the front. However, the observed MSTIDs are not in one-to-one correspondence with the model simulations, e.g., MSTIDs over the central U.S.A. in the models prefer to propagate southwestward while the MSITDs in the observations prefer to propagate southeastward. These discrepancies in TIDs are attributed to different upward airflow at the GW source and different background winds that influence propagation of the simulated GWs although the frontal large-scale structure in SD-WACCM-X is consistent with that in the North American Mesoscale Forecast System analysis.