Spatio-temporal rainfall patterns in Southern South America

The dominant spatial and temporal patterns of a network of 23 homogenous instrumental rainfall records of Southern South America were analysed and used to define four regional annual precipitation series: (1) Northwestern Patagonia (1950-2000) with nine stations from both side of the Andes between 41 and 44 degrees S; (2) Central Patagonia (1950-2000) with five Chilean stations between 45 and 47 degrees S; (3) Patagonian plains-Atlantic (1961-2000) with five Argentinean stations spread between 43 and 50 degrees S and from the eastern foothills of the Andes to the Atlantic coast and (4) Southern Patagonia (1950-2000) with four stations cast of the Andes, near the Strait of Magellan between 51 and 53 degrees S. Unique patterns were also identified for two of the southernmost stations in Ushuaia and Evangelistas (EVA). Time series analysis of these regional patterns shows marked decadal variability for Northwestern and Central Patagonia, 3-7 years oscillations for the Patagonian plains-Atlantic region and a strong biannual oscillation mode for Southern Patagonia. Regional annual rainfall appears to be strongly influenced by Antarctic circulation modes (Antarctic Oscillation Index), whereas the El Nino-Southern Oscillation (ENSO) influence on rainfall variability is less evident. Highly significant correlation of precipitation on the west coast of Patagonia with the pressure gradient between the subtropical eastern Pacific and the high-latitude south eastern Pacific is confirmed. Copyright (C) 2008 Royal Meteorological Society