Identification of Meteotsunami through GNSS Traveling Ionospheric Disturbance Observations

This study investigates the meteorological and ionospheric responses of a meteorological tsunamis (meteotsunamis) event that impacted southwest Kyushu, Japan on 25 February 2009. This event is identified by local sea-level pressure anomalies started at ~11:27 UT and lasted 18 hours with a maximum air pressure disturbance of ~1.5 hpa. Sea surface height anomalies were observed at ~13:00 UT and lasted for about 26 hours with a maximum perturbation of ~290 cm. Such perturbations of both sea level and sealevel pressure are likely associated with two subsequent traveling ionospheric disturbances (TIDs) events which were observed in total electron content (TEC) derived from ground-based Global Navigation Satellite System (GNSS) networks in Japan. The first TIDs occurred at ~11:41 UT which is 1.5 hr before the meteotsunami could be an early warning of meteotsunami. It has a wave front aligned in the northwest-southeast direction and propagated in the direction of southwest. This TIDs is more likely a manifestation of gravity waves (GWs) which might accelerate the growth rate of Perkins-type nighttime medium-scale TIDs (MSTIDs). The second TIDs took place at ~21:42 UT. Its wave front is characterized by concentric rings (referred to as CTIDs), likely corresponding to concentric GWs (CGWs). The characteristics of the CTIDs are corroborated with radar echo intensity measurements obtained from the Automated Meteorological Data Acquisition System (AMeDAS) and with the optimal waves source searching technique. Based on the radar echo intensity and optimal waves source searching results, the generation mechanism of the CTIDs could be meteotsunami and/ or deep convection. This suggests further investigation of ionospheric responses due to meteotsunami is needed.