CONICET | Buscador de Institutos y Recursos Humanos

Seasonality in Argentina is examined using precipitation observations from 56 weather stationsnorth of 42°S and CRU gridded precipitation. The Walsh and Lawler Seasonality Index (SI) andPrecipitation Concentration Index (PCI) are calculated to determine the different seasonalityregimes. The main characteristic is an east west gradient, where precipitation tends to bemore evenly distributed throughout the different months of the year in the east while rainfallin the west, is concentrated in 3 months or less. High replicability values indicate that thewettest month generally occurs during a same period of months in central and northernArgentina.Several stations in eastern humid Argentina have significant positive changes in the mean ofseasonality indices between 1961-1985 and 1986-2010, and increasing trend. In most casesthis lead to a change in the regime from rather seasonal with a short dry season to a seasonalregime. Through a PAM Clustering technique a new regionalization of precipitation seasonalityis obtained. The mean series in each cluster show a tendency towards more seasonal andhighly season regimes in all regions.The SI and PCI indices were calculated using the precipitation outputs of 18 global climatemodels from the Coupled Model Inter-comparison Project Phase 5 (CMIP5) to examine theability of these models to represent seasonality spatial distribution and changes in Argentina.To some extent the spatial distribution of seasonality are captured by models, however thereare considerable discrepancies in the location and extension of the east west gradient. Thesign and location of trends and changes in the mean SI and PCI are adequately reproduced inonly a few models. The low ability of GCMs to represent seasonality and its changes is aconsequence of the difficulties GCMs have simulating precipitation characteristics in Argentinareported by different authors.