Abstract
Tide gauge data were used to identify the occurrence, characteristics, and cause of tsunamis of meteorological origin (termed ‘meteotsunamis’) along the Western Australian coast. This is the first study to identify meteotsunamis in this region, and the results indicated that they occur frequently. Although meteotsunamis are not catastrophic to the extent of major seismically induced basin-scale events, the wave heights of meteotsunamis examined at some local stations in this study were higher than those recorded through seismic tsunamis. In June 2012, a meteotsunami contributed to an extreme water-level event at Fremantle, which recorded the highest water level in over 115 years. Meteotsunamis (wave heights >0.4 m, when the mean tidal range in the region is ~0.5 m) were found to coincide with thunderstorms in summer and the passage of low-pressure systems during winter. Spectral analysis of tide gauge time series records showed that existing continental seiche oscillations (periods between 30 min and 5 h) were enhanced during the meteotsunamis, with a high proportion of energy transferred to the continental shelf oscillation period. Three recent meteotsunami events (22 March 2010, 10 June 2012, and 7 January 2013) two due to summer thunderstorms and one due to a winter frontal system were chosen for detailed analysis. The meteotsunami amplitudes were up to a factor 2 larger than the local tidal range and sometimes contributed up to 85 % of the non-tidal water signal. A single meteorological event was found to generate several meteotsunamis along the coast, up to 500 km apart, as the air pressure disturbance propagated over the continental shelf; however, the topography and local bathymetry of the continental shelf defined the local sea-level resonance characteristics at each location. With the available data (sea level and meteorological), the exact mechanisms for the generation of the meteotsunamis could not be isolated.
Highlights
Meteorological tsunamis, or meteotsunamis, are similar to tsunami waves that are generated by seismic activity, except they have a meteorological origin (Rabinovich and Monserrat 1998; Rabinovich 2009; Rabinovich et al 2009; Pasquet et al 2013)
A single meteorological event was found to generate several meteotsunamis along the coast, up to 500 km apart, as the air pressure disturbance propagated over the continental shelf; the topography and local bathymetry of the continental shelf defined the local sea-level resonance characteristics at each location
This study used data from coastal tide gauges located along the south-west coast of Western Australia to examine the occurrence of meteotsunamis, defined as waves with periods \6 h that were related to local weather conditions
Summary
Meteorological tsunamis, or meteotsunamis, are similar to tsunami waves (defined as long or shallow-water waves, where the wave length, L, is much greater than the water depth, h) that are generated by seismic activity, except they have a meteorological origin (Rabinovich and Monserrat 1998; Rabinovich 2009; Rabinovich et al 2009; Pasquet et al 2013). Meteotsunamis have similar periods to seismic tsunamis (Monserrat et al 2006). Meteorological disturbances, such as squalls, tornadoes, thunderstorms, frontal passages, and atmospheric gravity waves, can produce these longer-period surface waves, either locally or remotely. The main forcing mechanism of a meteotsunami is the propagation of an abrupt change in sea surface atmospheric pressure and/or associated wind gusts. Monserrat et al (2006) described several large meteotsunamis, which occurred worldwide, and their generating mechanisms in their study on meteotsunamis
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