ABSTRACT

Machado, A.A. and Calliari, L.J., 2016. Synoptic systems generators of extreme wind in southern Brazil: atmospheric conditions and consequences in the coastal zone. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1182 - 1186. Coconut Creek (Florida), ISSN 0749-0208.

The coast of Rio Grande do Sul (RS), southern Brazil, suffers a seasonal variation due to the dynamics associated with the frequency and intensity of storms. These storms are mostly associated with high intensity extratropical cyclones that generate wind waves which can change a beach profile from its maximum accretion state to complete erosion during a period that can vary from few hours to a few days. Using the Generalized Pareto Distribution, we observe that the 0.01 probability density value of all the wind speed values studied was 17 ms−1. Analyzing the storms that generate extreme winds (ie ≥ 17 m s−1), an increase in the number of extreme events to the coast of RS was observed over the past 66 years (1948–2013). The increase in the frequency of extreme events of wind, will modify and increase flooding, storm surge, and erosion along the coast. It was observed that the main weather systems generating strong winds to the shore of the RS are extratropical cyclones, which are mainly formed between parallels 30°S to 40°S, with two preferred trajectories, east and southeast, generating both erosion and storm surges. The majority of extratropical cyclones presentend propagation velocities between 20–40 km h−1 (61.97%). The months with the highest number of extreme events were June (22), followed by October (16). The consequences of storms in RS coast were: erosion of 45 m3m−1, storm surge of 1.88 m, wind speed of 26.21 m s−1 and significant wave height of 8.79 m.

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