Extreme precipitation events in the Austral Chaco region of Argentina

LOVINO, MIGUEL A.; MÜLLER, GABRIELA V.; PIERRESTEGUI, MARÍA JOSEFINA; ESPINOSA, EDNA; RODRÍGUEZ, LETICIA

INTERNATIONAL JOURNAL OF CLIMATOLOGY

JOHN WILEY & SONS LTD

Año: 2022 vol. 42 p. 5985 - 6006

0899-8418

This study assesses the intensity, spatial distribution and temporal variabilityof extreme precipitation events (EPEs) on different time scales relevant to agricultureand water resources during the 1901?2016 period over Argentina´sAustral Chaco (ACh). EPEs were identified using a nonparametric approachfor the Standardized Precipitation Index (SPI). The leading modes of SPI´s variabilitywere detected using the Singular Spectrum Analysis. We also compileand control the quality of precipitation observations in a scarcely monitoredregion. The limited number of stations conditions the interpolation of theGPCC v2018 database here used, mainly during the early twentieth century.The EPEs characterized by SPI at a 24-month time scale, which favour longlastingwater excesses or deficits with hydrological impacts, underwent two differentiatedlong-term periods: a dry one before 1960 and a wet one from 1960to 2005. Consistently, seasonal wet EPEs were more frequent during the wetperiod while seasonal droughts were more frequent and with larger spatialextent during the dry period. Seasonal EPEs, represented by the SPI at3-month time scale, can impact agriculture during the crops´ critical growthperiod. Since 2006, the long-term wetting trend has been reversed. If thisbehaviour continues into the coming decades, more droughts and less wetnessmight be expected. The EPEs present a large interannual variability with 6.3-and 9-year significant cycles that, combined with long-term trends, favouredextremely wet/dry EPEs. Most of the wet/dry EPEs occurred during El Niño/La Niña events. Although this relationship is not straightforward, we found adiscriminant ENSO signal between October of the year when an ENSO eventstarts and February of the next year. Finally, severely dry/wet EPEs tend tohave large spatial extent in the ACh region. The central-eastern ACh regionexperiences the most extreme wet and dry conditions, which makes this areamore prone to extreme EPEs.