A Multi-Platform Investigation of Typhoon-Induced Vertical Atmosphere–Ionosphere Coupling Over Japan Using Himawari-9, ERA5, GEONET GNSS, COSMIC-2, and Swarm Observations

Understanding how energy generated by intense typhoon convection may couple the lower atmosphere to the ionosphere remains an important challenge in atmosphere–ionosphere coupling research. This study presents a multi-platform observational framework to investigate possible vertical atmosphere–ionosphere coupling associated with major typhoons affecting Japan using Himawari-9, ERA5, GEONET GNSS, COSMIC-2, and ESA Swarm observations. Five intense typhoons—Nanmadol (2022), Khanun (2023), Lan (2023), Shanshan (2024), and Krosa (2025)—are selected based on their impact on Japan and the availability of complementary multi-platform observations. Himawari-9 observations are used to characterize cloud-top brightness temperature, convective evolution, and storm development. ERA5 reanalysis provides temperature, pressure, relative humidity, geopotential height, and horizontal and vertical wind fields for characterizing the neutral atmospheric response and estimating atmospheric gravity-wave (AGW) potential energy. The dense GEONET GNSS network is used to derive Vertical Total Electron Content (VTEC) variations and examine spatial and temporal ionospheric responses associated with the selected typhoons. COSMIC-2 radio occultation observations provide vertical electron-density profiles and F-region parameters, including peak electron density (NmF2) and peak height (hmF2), allowing altitude-dependent changes in the ionosphere to be investigated. Independent ESA Swarm observations of electron density, electron temperature, plasma drift, and magnetic-field intensity provide complementary measurements of topside ionospheric variability. By combining observations from the troposphere, middle atmosphere, F-region, and topside ionosphere, the framework enables systematic investigation of the temporal evolution, altitude dependence, spatial distribution, and consistency of atmospheric and ionospheric perturbations during major typhoon events. Particular attention is given to the relationship between enhanced convection, AGW activity, GNSS-derived VTEC variability, F-region plasma redistribution, and topside ionospheric disturbances. The study provides a comprehensive observational approach for assessing possible typhoon-associated atmosphere–ionosphere coupling over Japan while avoiding causal interpretation based solely on temporal coincidence.