El Niño–Southern Oscillation incidence over long dry sequences and their impact on soil water storage in Argentina

Abstract

The deficit of daily precipitation, persistent over time (long dry sequences [LDS]), causes economic losses in the east–northeast of Argentina where agriculture production is the main economic activity. For this reason, an improvement in the seasonal prediction of the frequency of precipitation is required. Among several forcings influencing the region of study, El Niño–Southern Oscillation (ENSO) has been identified as responsible for a great part of the inter-annual variability of precipitation. Therefore, in this study, we assess the ENSO signal on LDS and the response of soil water storage under the different phases. In order to assess this issue, daily data were used from 30 meteorological stations. Based on this information, dry sequences were quantified considering a dry day when the accumulated precipitation of two consecutive days was lower than 5 mm. From the dry sequences, two different thresholds were used to identify LDS. On one hand, the 85th percentile was selected as a spatially variable threshold and, on the other hand, 15-day length was used as a fixed one. Based on this selection, the severity and the number of LDS were analysed. In general terms, La Niña (El Niño) phase presents higher (lower) severity and higher (lower) probability in the occurrence of more than one LDS per season, except in winter. This result is in concordance with negative (positive) anomalies of accumulated precipitation under La Niña (El Niño) phase. Regarding the impact on the water balance, soil water storage responds to accumulated precipitation anomalies in all the seasons.