CONICET | Buscador de Institutos y Recursos Humanos

During the last decades, the main climatic variables with strong agricultural impact (temperature and rainfall) have varied both spatially and temporally. In the study area, east-northeast of Argentina, several authors observed increases in annual rainfall and inhomogeneous seasonal rainfall behaviour, depending on the region and time of year. In a changing climate system, the magnitude of the change could have modified the climate of the region. Given this hypothesis, initially we quantified the temporal variability of the variables involved in different climatic classifications, focusing on extreme events. Then, we evaluated whether these classifications are sensitive to the observed changes. From the various existing methodologies, two climate classifications were analyzed: Köppen-Geiger, which considers minimum and maximum rainfall per semester, and Thornthwaite, based on the water balance components. In order to evaluate longer time series in the region, representative stations were used and two excluded periods were considered: 1940-1970 and 1980-2010. To define extreme events, for each variable and semester (warm: ONDJFM; cold: AMJJAS), 1st and 9th deciles were used for the period 1940-2010. Firstly, we evaluated if the minimum and maximum rainfall per year has been an extreme event. The main results show that the number of extreme events of maximum rainfall has increased in the western stations between 30% (Villa Dolores) and 50% (Laboulaye) while it has decreased 50% in the center (Rosario). Changes in extreme events of minimum rainfall are more relevant during the warm semester, doubling for central (Rosario) and eastern (Buenos Aires) stations. In the mean values, there has been a greater difference in minimum rainfall between warm and cold semester for the second period. However, these differences were not enough to show a change in Köppen-Geiger sub-classification. By contrast, the relationship between the maximum rainfall of warm semester and minimal rainfall of cold one still indicates the absence of a dry season, except for the western region (e.g.Córdoba). These results depend only on the mean values, even though changes in mean conditions and extreme events may be connected. With respect to Thornthwaite classification, changes in the analyzed variables lead to modifications in the water balance, showing the second period wetter than the first one. In effect, Moisture Index shows the impact of these changes: some of the eastern stations changed from "humid-wet" to "wet" while some western stations changed from "humid-dry" to "wet humid". The western region presents wetter conditions in mean terms while the number of extreme minimum rainfall has not significantly decreased. This high variability highlights the vulnerability of this area in terms of agricultural planning. On the other hand, in the eastern region, there were increases in both the average and extreme conditions. In general, changes would indicate a transition to a wetter climate and stronger seasonality.

enviar mensaje