Squall-line caused meteotsunamis over Finnish sea areas

Meteotsunamis are tsunami-like waves caused by mesoscale atmospheric disturbances that induce a moving air pressure anomaly over water. The speed and direction of the disturbance and the shape and topography of the coastal waters influence the resonance that can increase the wave height. If the speed of the air pressure disturbance is close to the long wave phase speed in shallow water, the resonance increases the wave height. Meteotsunamis can be generated by a phenomenon such as a cold front, a thunderstorm or a squall line.

 

Finland is favorable location for meteotsunami formation because of shallow depths over Finnish coastal waters. A few studies of meteotsunami occurrence have been published in Finland. Pellikka et al. (2020) investigated summer period meteotsunamis on the Finnish side of the Gulf of Finland and Pellikka et al. (2022) made a classification of meteotsunami cases according to season by studying high-frequency sea level variations from 2004–2015 on the Finnish coast.

 

In this study, we analyze occurrence of meteotsunamis over the Finnish sea areas in 17 squall line situations. The radar-observed evolution of the squall lines is analyzed and their movement speeds and tracks are compared to the water depths. Observations from 13 tide gauges operated by the Finnish Meteorological Institute on the Finnish coast are used to analyze meteotsunami events. The motivation of this study is to increase understanding of the squall line speeds, track lengths and directions that may cause meteotsunamis at the Finnish sea areas. These findings may help us to forecast meteotsunami events in the future.