Trends and jumps in the annual precipitation in South America, south of the 15°S

Abstract

Different types of South American annual precipitation series are analyzed for stations located south of the parallel 15ºS. It has been found that the most typical pattern of change in the long-term averages for 30-years consecutive series, corresponding to meteorological stations eastward of the Andes Cordillera, is represented by a "jump" or discontinuity which, for these stations, is always positive. The maximum signal is spotted between the 1950's and the 1960's, showing the largest values on the continental zone of Argentina's territory. On the other hand, for stations on the windward side of the Andes, in Chile, the change is characterized by a decreasing tendency during the years, being steeper over the Northern dessert. Evidences of impacts produced by these changes are shown and possible physical causes of these long-term changes are inferred.