Synoptic characterization of extreme wind-wave events in Chile

Storm surges are phenomena caused by wind conditions of greater magnitude than usual, whether local or remote. The ocean-atmosphere interaction is important in the development of these events, since wind is the main factor that increases wave heights, leading to an increase in their energetic potential. For this reason, the study focuses on characterizing the meteorological conditions that triggered swells categorized as M3, M4 and M5 of the Escala de Impactos de Marejadas developed by the MarejadasUV (MUV) of the University of Valparaíso in the northern, central and southern areas of the country.
Three representative points were selected on the coasts of Chile: in the north (-23°S,72°W), in the center (-32°S,75°W) and in the south (-44°S,78°S). Datasets were extracted every 3 [hrs] for significant wave height, mean period, mean direction and wave energy spectra modeled with WaveWatch III forced with surface wind and sea ice area fraction from the ERA5 reanalysis. With these data, thresholds related to 2, 5 and 10 years of return period were obtained to categorize the events into M3, M4 and M5, respectively, that occurred between May and October from 1979 to 2022, obtaining 29 cases in the north, 28 in the center and 21 in the south.
The northern area was characterized by more remote swell events (24) than local (5). The latter have a similar configuration where the south winds (more commonly known as Surazo) developed swells of the three categories, with different wind magnitude. The remote events were generated by low pressure (LP) formed at different points of the study area mainly located below the 40°S in deep water. In the center area, there were a greater number of local events (8), which in addition to being formed by south winds were also formed by LPs developed near the study point and the shore. This last configuration being similar for the remote events (20), but the distance which they were developed was greater. In the southern area, there were more local events (17) than remote events (4), mainly formed by a LP that were formed nearly the study point.
In conclusion, the categorization of these events depends on the wave climate. Most of the local events in the north and center were formed by winds from the south. The rest of the events are developed by LPs originated in different parts of the study area.