Aplicación de un índice para el análisis de la características de la estación lluviosa en la región subtropical de Argentina

the main objective of this study is to identify the dates of the onset and end of the rainy season in argentina north of 30°s, through an appropriate index, and to analyze its interannual variability in homogeneous regions with respect to the temporal variability of precipitation. we used daily precipitation data from 19 pluviometric stations in argentina provided by the national weather service for the period 1974-2004, and zonal wind data at the level of 850 hpa derived from ecmwf (era-40) for the period 1979-1999. the dates of the onset and end were established for each station through a rainfall accumulation criterion. this criterion is adequate to analyze regions which have an accentuated rainfall annual cycle. the analysis of the interannual variability of the rainy season's series showed that both regions have a trend towards an extension in length. we found that changes in the low level zonal wind, from positive values (from mid-april to early september) to negative values (early september to mid-april), represent the climatological onset and end of the rainy season.