Meteorological Tsunami Generation Due to Sea‐Surface Pressure Change: Three‐Dimensional Theory and Synthetics of Ocean‐Bottom Pressure Change

Abstract

While disastrous tsunamis are mostly generated by large earthquakes, some tsunamis are excited by pressure disturbances at sea surfaces caused by meteorological phenomena such as storms and moving convective systems (e.g., Churchill et al., 1995;Monserrat et al., 2006). Such tsunamis are known as meteorological tsunamis or meteotsunamis. The basic generation mechanism of a meteorological tsunami was theoretically investigated in two-dimensional (2-D) space with long-wave approximations (e.g.,

Global fast-traveling tsunamis by atmospheric pressure waves on the 2022 Tonga eruption

“…We then simulated the generation and propagation of ocean waves driven by the atmospheric pressure waves (11,12) using global bathymetry data (13). We finally calculated the ocean-bottom pressure changes (pbot) as the sum of the atmospheric pressure (patm) and the sea-surface height changes η (peta = ρwg0η, ρw: seawater density, g0: gravity acceleration, 9.8 m/s 2 ): pbot = patm + peta (12,14).…”

“…3B), in which its wavefront spreads at the theoretically predicted tsunami velocity c0 = (g0h0) 0.5 (g0: gravity acceleration, h0: seawater depth). This wave is expected to be a result of water volume conservation (14,15) (fig. S7, Movie S2).…”

“…Because the pressure change at the ocean's bottom caused by this leading wave is a superposition of the pressure changes caused by the Lamb wave and tsunamis, pbot = patm + peta (12,14), the ocean-bottom pressure does not directly represent the tsunami height, whereas the coastal tide gauges observe only the sea height changes but not the atmospheric pressure. This makes it difficult to accurately calculate the tsunami height from global ocean-bottom pressure gauges.…”

“…The external force term, including the atmospheric pressure patm, drives the tsunami. After the calculation, we calculated the ocean-bottom pressure pbot by the sum of the pressure changes due to the atmospheric pressure change patm and because of the sea-surface height change peta = ρwg0η (12,14), expressed as:…”

Characteristics of Tsunamis Observed in Japan due to the Air Wave from the 2022 Tonga Eruption

“…Similar air-sea waves had previously been generated by the Krakatoa volcano eruption in 1882 (Harkrider and Press 1967), and the authors indicated that the air wave propagated at a velocity of 312 m/s. This kind of air-sea coupled waves, which is often called to meteotsunamis, has already been studied without volcanic eruptions (Hibiya and Kajiura 1982; Fukuzawa and Hibiya 2020; Kubota et al 2021). Saito et al…”