Analysis of extreme wind events in the Weddell Sea region (Antarctica) at Belgrano II Station

Abstract

The objective of the present work is to analyze the wind pattern (direction and speed) at Belgrano II Station, evaluating the influence of large-scale atmospheric systems on extreme wind speed events. The study area is the Weddell Sea, located at the southern end of the Atlantic Ocean, between latitudes of 83° S and 55° S and longitudes of 84° W and 20° E. Daily meteorological data were used in the period from 1979 to 2015, whose variables are: Sea Level Pres-sure (SLP), Wind Speed (WS), Wind Direction (WD) and Air Temperature at 2 Meters (T2M), collected at Belgrano II Station, under the care of the Ar- gentine Antarctic Institute (AAI). To analyze the anomalies in the fields of air temperature, atmospheric circulation and surface pressure on a large scale, we used the reanalysis data obtained from the ERA-Interim database, which are: air temperature at 2 m (oC), geopotential height (m) at the 500 hPa level, and zonal and meridional components of wind (ms−1) on the surface. The ex-treme event was defined as values above the 95% percentile of each month of the year. The results indicate that the wind direction at Belgrano II Station was predominantly southeast. However, when the wind speed was predominant from the northeast, approximately 20% of the cases presented wind speeds above 16 ms−1. Therefore, when there is a change in synoptic conditions near the Belgrano II station, the predominance of the winds becomes northeasterly, with an intensification in its speed. An extra-tropical cyclone approaching the Belgrano II region caused the wind to become of the northeastern on the days before the extreme event, so that two days beforehand there was an increase in air temperature in surface. When we analyzed the wind speed in Belgrano II, we identified that there was not a marked change and over the years, however, we identified that the seasonality presented changes, with more intense winds between the months of May and September.