Identification of Meteotsunami through GNSS Traveling Ionospheric Disturbance Observations

Ionospheric total electron content (TEC) derived from dual-frequency GNSS receiver measurements has been used to detect and characterize ionospheric disturbances with forcing originated from ground seismic motion, open ocean tsunami events, and atmospheric waves. This paper will focus on the detection and characterization of ionospheric disturbances due to meteorological tsunamis (meteotsunamis). A meteotsunami is a fast-moving tsunami caused by atmospheric disturbances along the water surfaces of coastal areas of oceans and lakes. It is the result of energy coupling between the atmosphere and water surface driven by air pressure perturbations and wind stress and is constrained by the coastline shape and bathymetric conditions. Understanding of meteotsunami’s characteristics such as the ionospheric TEC disturbance magnitude and propagation speed will enable the development of detection and forecasting techniques and early warning systems.

This study investigates the meteorological and ionospheric responses of a possible meteotsunami 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 ~100 cm. Such perturbations of both sea level and sea-level pressure are likely associated with two subsequent traveling ionospheric disturbance events (TIDs) which were observed in TEC derived from ground-based Global Navigation Satellite System (GNSS) networks in Japan. The first TID occurred at ~11:41 UT. It has a wave front aligned in the northwest-southeast direction and propagated in the direction of southwest. This TID is more likely seeded by a gravity wave which might accelerate the growth rate of Perkins-type nighttime medium-scale traveling ionospheric disturbances (MSTIDs). The second TID took place at ~21:42 UT. Its wave front is characterized by concentric rings (referred to as CTID), likely corresponding to concentric gravity waves (CGWs). The characteristics of the CTIDs are corrobated with radar echo intensity measurements obtained from the Automated Meteorological Data Acquisition System (AMeDAS). Further studies using the optimal waves source searching technique suggest that the CTID is possibly induced by a meteotsunami. Currently there exists no reliable early warning system for meteotsunamis; the science community requires new technological advancements to overcome current limitations.