Contribution of Precipitation and Potential Evapotranspiration to Long-Term Changes in Aridity in Argentina Over Recent Decades

Over recent decades, aridity has intensified in Argentina because of an imbalance between precipitation and atmospheric evaporative demand, yet the relative role of these factors in long-term changes remains poorly explored. This study analyses precipitation (PRE) and potential evapotranspiration (PET) contributions to aridity changes across Argentina during 1961–2020. Using monthly precipitation and mean temperature data from the Climatic Research Unit (CRU), the United Nations Environment Programme (UNEP) aridity index (AI) was calculated at annual and seasonal scales. Subsequently, linear and nonlinear trends, climatic shifts, and PRE and PET contributions to AI changes were evaluated for six regions using fixed 30-year periods and pre- and post-shift means. The results show a widespread decrease in annual AI across much of Argentina (1–10% per decade), driven primarily by PRE reductions and, to a lesser extent, by PET increases. Seasonally, AI increases prevail in summer and autumn (locally > 30% per decade), decreases in winter (1–30% per decade), and a mixed pattern emerges in spring (-20 to 10% per decade), with PRE as the dominant control. Nonlinear variability in the AI is controlled by PRE, with the strongest declines observed in the Andean and Extra-Andean Patagonia (-2.9 and − 2.3% per decade), associated with PRE decreases and PET increases. In contrast, the Northwest and Subandes regions show the greatest seasonal variability, with summer AI increases (7–16% per decade) and abrupt shifts (70–83%), whereas in East PET increases (> 3.4%) exceed the PRE contribution and account for more moderate AI declines (-2.5%). Overall, aridification in Argentina is primarily governed by PRE changes, while PET acts as a regional and seasonal amplifier, highlighting the need for an integrated water-balance approach to assess aridity and its impacts.