A CHARACTERIZATION OF WIND VARIABILITY FROM SEASONAL TO INTERANNUAL SCALES IN THE VICINITY OF THE RíO DE LA PLATA

SIMIONATO, C. G.; VERA, C. S.; SIEGISMUND, F.

Mar del Plata, Argentina

Congreso; Joint Assembles of the International Association for Physical Sciences of the Oceans and International Association for Biological Oceanography - XII Coloquio Argentino de Oceanografía; 2001

IInternational Association for the Physical Sciences of the Oceans

Previous works have indicated that the Río de la Plata estuary variability is highly dominated by the surface winds. However not much is known either about the wind seasonal cycle or its interannual variability in that small but important area. In this paper the wind variability on those scales at the Río de la Plata influence area is characterized using 50 years NCEP 10-m wind reanalyses. The mean seasonal cycle, its interannual variability and the long period trends observed along the year as well as their effect on the estuarine circulation have been analyzed. It was found that over that particular area winds exhibit an intense seasonal cycle characterized by onshore winds during austral summer and offshore winds during austral winter. The pattern for spring has a feature that resembles the summer, but with lower velocities while the fall is clearly a transition season with relatively small winds. On interannual time scales, three distinctive modes of variability have been found with periods of around 5, between 8 and 10 and around 16-17 years. Those modes seem to be related to characteristic signals on sea surface temperature and sea level pressure. On longer time scales, an increase on both winter and summer wind speeds has been detected over the last 50 years, meanwhile during the intermediate seasons the data display an important change on the wind direction. The impact of those modes on the local oceanic circulation as simulated with HamSOM numerical model will be discussed in the presentation.