The aim of this study was to classify and characterize the climate of the Pampas, a vast region in the centre of Argentina. Due to its territorial extension, a climatic zoning of the region was performed, based on the topography and the most relevant climatological parameters. Climate data from 33 stations of the National Meteorological Service were analysed considering the period 1960–2010. A cluster analysis from the hierarchical method of Ward with an interval squared Euclidean distance as a measure of dissimilarity was applied. The obtained clusters responded to the north–south temperature gradient of the Pampas, influenced by geographical features such as the Tandilia and Ventania hills in Buenos Aires Province and the Pampean hills in Córdoba. Precipitation had a northeast–southwest gradient, and the influence of the arid southwest diagonal of the Pampas was appreciated by determining a semi‐arid environment. The proximity to the sea marked the average humidity values, whereas the winds of strong intensity were registered in the south and west of the region. On the other hand, the standard precipitation index was calculated to identify wet and dry cycles in each cluster. It allowed to characterize these events considering frequency, periodicity, duration and intensity, resulting in the definition of eight climatic subregions.

RESUMEN. La Región

The south of , as most of Argentina, is a semiarid region. Its economy is based on rain-fed agriculture and livestock. Traditionally, the climate has been studied considering the analyses of monthly and annual climate parameters, but there is evidence that in this type of areas, the short-term climatic events have a substantial impact on the climate. Therefore, this study aimed at developing a climate regionalization from the analysis of daily temperature and precipitation extremes in the south of the Pampas for the period 1970-2017. Subsequently, it focuses on analyzing both trends and breakpoints of these events in the different sub-climates. To do so, we applied a Cluster-based Principal Component Analyses with a Ward hierarchical supervised method to generate a climate regionalization considering 29 daily extreme climatic indices and the elevation. We identify four sub-regions, and we analyzed trends during 1970-2017, and in the two-time series defined by applying breakpoints. Both minimum and maximum temperatures and precipitation had structural changes in the last 15 years, exposing the region to warming and dryness trends. The maximum temperature increases 0.5ºC, while precipitation decreases 30 mm. The short-term climate variability allows us to identify areas climatically more detailed and to conclude that the south of the Pampas is characterized by its high dependency on short-term climatic events. Regionalización y tendencias climáticas basadas en eventos extremos térmicos y pluviométricos diarios en el sur de la Región Pampeana (Argentina)RESUMEN. El sur es, al igual que la mayor parte de Argentina, una región semiárida. Su economía se basa en la agricultura de secano y la ganadería. Tradicionalmente, el clima Ferrelli et al. 394Cuadernos de Investigación Geográfica 45 (1), 2019, pp. 393-416 ha sido estudiado considerando los eventos térmicos y pluviométricos mensuales y anuales. Sin embargo, existe evidencia científica de que los eventos climáticos a corto plazo (diarios) tienen un impacto sustancial en el clima. El objetivo de este trabajo es desarrollar una regionalización climática a partir del análisis de las temperaturas y precipitaciones diarias extremas en el sur de la Región Pampeana durante el período 1970-2017. Complementariamente, este trabajo se enfoca en analizar las tendencias de estos eventos en cada sub-clima durante dos períodos de tiempo de la serie 1970-2017. Para generar la regionalización, aplicamos un Análisis de Componentes Principales y un Análisis de Conglomerados utilizando el método supervisado de Ward, considerando 29 índices climáticos extremos diarios y la elevación. Como resultado obtuvimos cuatro subregiones. Además, analizamos la tendencia de los 29 índices climáticos extremos diarios durante el período 1970-2017 y en dos sub-series dentro de este período definidas mediante la aplicación de puntos de interrupciones o cambios estructurales. En el sur de la región Pampeana, la temperatura y la precipitación presentaron cambios estructurales en los últimos 15 años, lo q...