Atmospheric Wave Trains Due to the Eruption of Hunga Tonga–Hunga Ha’apai on January 15, 2022 Detected by Himawari-8

We analyzed the propagation of atmospheric waves generated by the eruption of Hunga Tonga–Hunga Ha’apai on January 15, 2022 using infrared images acquired by Himawari-8. We used a sequence of high-frequency scanning imagery of the Japan region having a time interval of 2.5 minutes. We calculated the anomaly of the brightness temperature (Tbb) through temporal double integration after taking the second-order time derivative of Tbb. From the temporal–horizontal distribution of the Tbb anomaly, we searched for waveforms by data stacking. As a result, we detected Lamb mode in all infrared channels from Band 7 to Band 16. The Pekeris mode was visualized behind the Lamb mode in Band 12 and the Band 12 − Band 13 difference but was difficult to see in Bands 8, 9, and 10 corresponding to the mid-troposphere. The wave train as an internal gravity wave (IG-train) behind the Pekeris mode was visualized in each band, especially clearly in Band 12 and the Band 12 − Band 13 difference. The IG-train had a period range of 10–15 minutes, corresponding to that of the observed ground pressure. The phase velocity of the IG-train was estimated to be 199.1 ± 10.0 m/s, which is a typical speed of the tsunami phase propagating in the Pacific Ocean. The passage of the IG-train corresponded well with ground pressure variations and the peak tidal oscillations observed as volcanic meteotsunamis along Japan's Pacific coastline.