Atmospherically induced large amplitude sea-level oscillations on October 29, 2019 at Santa Catarina, Brazil
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Atmospherically induced large amplitude sea‑level oscillations on October 29, 2019 at Santa Catarina, Brazil C. E. S. Araujo1 · M. G. Boll1 · L. H. P. Garbossa1 · A. Vanz1 · R. N. Candella2 Received: 31 January 2020 / Accepted: 9 October 2020 © Springer Nature B.V. 2020
Abstract Several strong sea-level oscillations in the southern region of Brazil with periods in the range of tsunamis, but attributed to atmospheric disturbances, have been publicized in the media or in scientific articles in recent years. However, only a few were registered by instruments. On October 29, 2019, a squall line, linked to an atmospheric storm and a positive jump in atmospheric pressure, spread from south to north along the coast of Santa Catarina. The atmospheric disturbance generated, through Proudman’s resonance mechanism, at least two tsunami-like waves with heights greater than 0.70 m and periods around 15 min. These waves were recorded by a network of tide gauges, allowing to monitor their evolution and transformations for more than 200 km. Although there were no reported fatalities, there were significant material losses linked to this occurrence. The objective of the present work is to analyze and connect atmospheric conditions and wave signals in order to further understand the circumstances leading to the formation of this type of event in the southern coast of Brazil. Keywords Tsunami-like waves · Brazil · Southern region · Squall line
1 Introduction Meteotsunamis are sea-level oscillations with the same temporal and spatial scales as ordinary tsunami waves and can sometimes affect coastal areas in a similarly destructive way (Monserrat et al. 2006). They are generated by traveling atmospheric disturbances such as frontal passages, gravity waves, squall lines and significant pressure jumps (Bailey et al. 2014). Due to the inverted barometer effect, sudden atmospheric pressure jumps cause changes in sea level and create propagating ocean waves. When the propagation speed of the pressure perturbation matches the speed of the ocean wave, resonant energy transfer mechanisms induce an increased sea-level response (Vilibic et al. 2016; Bailey et al. 2014). The * C. E. S. Araujo [email protected] 1
Empresa de Pesquisa Agropecuária e, Extensão Rural de Santa Catarina EPAGRI, Florianopolis, SC, Brazil
2
Instituto de Estudos do Mar Almirante Paulo Moreira, Arraial do Cabo, RJ, Brazil
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Vol.:(0123456789)
Natural Hazards
main mechanisms at the generation areas are the Proudman resonance (Proudman 1929) and the Greenspan resonance (Greenspan 1956). Pattiaratchi and Wijeratne (2014) noticed that stronger amplification could also be due to topographical resonance, which occurs when the natural oscillating period of continental shelf or enclosed or semi-enclosed bays and harbors is equal to the periods contained in a meteotsunami. The southern South America Atlantic continental shelf (including the southern Brazil coast) is wide, relatively shallow and aligned with the displacement direction of the lowpressure
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