Vorticity and pressure anomalies in the western Mediterranean during El NiñO/Southern Oscillation extremes

Abstract

By means of a statistical study of percentiles, applied to bi-monthly seasons of composite 2-year periods centred in the year of occurrence of a warm or cold ENSO extreme, we show the climatic influence of these events on the western Mediterranean area. The study is developed over a 30-year period (1961–1990). The variables used are the number of cyclonic days and the number of days having negative pressure anomalies in the area. Daily sea-level atmospheric pressure data have been used to estimate both daily mean wind and vorticity in the study zone. The main influence found is that after a warm extreme year, during the March–April bi-month, there is a decrease in the number of days with both cyclonic circulation and negative pressure anomaly. © 1997 by the Royal Meteorological Society. Int. J. Climatol. 17: 475–482, 1997.