Tropical Cyclone-Induced Gravity Wave Perturbations in the Upper Atmosphere: GITM-R Simulations

The tropical cyclone (TC)-induced concentric gravity waves (CGWs) are capable of propagating upward from convective sources in the troposphere to the upper atmosphere and creating concentric traveling ionospheric disturbances (CTIDs). To examine the CGWs propagation, we implement tropical cyclone-induced CGWs into the lower boundary of global ionosphere-thermosphere model with local-grid refinement (GITM-R) and simulate the influence of CGWs on the ionosphere and thermosphere. GITM-R is a three-dimensional non-hydrostatic general circulation model for the upper atmosphere with the local-grid refinement module to enhance the resolution at the location of interest. In this study, CGWs induced by the typhoon Meranti in 2016 have been simulated. Information of the TC shape and moving trails is obtained from the TC best-track dataset, and the gravity wave patterns are specified at the lower boundary of GITM-R (100 km altitude). The horizontal wavelength and phase velocity of wave perturbation at the lower boundary are specified to be consistent with the TEC observations. The simulation reveals a clear evolution of CTIDs, which shows reasonable agreement with the GPS-TEC observations. This is the first time the typhoon-driven TEC perturbation has been simulated in a general circulation model. To further examine the dependence of the CTIDs on the wavelength and frequency of the gravity wave perturbation at the lower boundary, different waveforms have been tested as well. The magnitude of CTIDs has a negative correlation with the period but a positive correlation with the wavelength when the horizontal phase velocities are sufficiently fast against the critical-level absorption.