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Meteorological Tsunami of 19 March 2017 in the Persian Gulf: Observations and Analyses

On 19 March 2017, destructive tsunami-like waves impacted the northeast shore of the Persian Gulf (PG). The maximum surveyed runup of about 3 m was observed at Dayyer in southern Iran, where damaging waves inundated the land for a distance of * 1 km and resulted in the deaths of five people. Because the PG has always been considered safe from extreme oceanic waves, the event was totally unexpected. In this study, we examined sea level data from 12 stations across the PG and a variety of meteorological information, including satellite imagery, high-altitude isohypse maps and high- resolution air pressure records from 47 instruments along the PG. Our results show that the event was very local, with recorded maximum trough-to-crest wave heights of 197 cm at Dayyer and 234 cm at Asaluyeh, nearfield cities in Iran located * 80 km apart. The dominant wave periods were in the range of 15–20 min. At all distant tide gauges, the observed wave heights were \35 cm. No earthquakes or landslides were evident at the time of the event. On the other hand, atmospheric processes during 18–22 March were very active and 10 distinctive tsunamigenic air pressure disturbances were observed propagating over the PG, suggesting that the event of 19 March 2017 was a ‘‘meteorological tsunami’’. Atmospheric conditions over the PG were highly favourable for the generation of meteotsunamis and very similar to those that caused a chain of strong meteotsunamis in the Mediterranean and Black Sea regions during 23–27 June 2014. Based on the 500 hPa wind, we evaluated that the disturbances had propagation speeds of 21–38 m/s, with the disturbance at Dayyer having a speed of * 26 m/s toward 77 True. The Froude number, Fr (estimated as the ratio of the air disturbance speed to the long wave speed), on 19 March 2017 in the Dayyer/Asaluyeh region was close to resonance, Fr * 0.9 to 1.1, which is highly favourable for meteotsunami generation. Our findings indicate that the Dayyer/Asaluyeh area is a ‘‘hot spot’’ that is highly vulnerable to extreme, weather-induced tsunami-like waves.

Persian Gulf, meteotsunami, extreme waves, atmospheric waves, tide gauge data, wavelet analysis, remote sensing

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