The Relative Contribution of Precipitation and Temperature in Droughts in Central-Southern Chile (29°-42°S), and Detecting its Time of Emergence (ToE)

Abstract Submission: Managing water resources under droughts represents a human challenge that affects agriculture, industry, and environmental conservation. Even worse, droughts are intensifying and becoming more recurrent due to climate change. To cope with droughts, improving our understanding of hydrological processes and changes, which also requires to have quantitative information for land-use planning decision-making. The Time of Emergence (ToE) determines when a significant deviation from climate variability occurs and has been proposed as a tool to project when and where unprecedented changes will happen. ToE is mostly estimated at a broad scale, however, drought decision-making and adaptation strategies are implemented at basin scale. This study uses the Standardized Precipitation-Evapotranspiration Index (SPEI, in particular annual-scale SPEI-12) to determine the overall and relative effects of changes in precipitation (Pr) and temperature (that affects Potential Evapotranspiration, PET) over droughts. The ToE of SPEI was estimated over 10-cities in central-southern Chile (29°-42°S). Projections from 30 General Climate Models (GCMs) under SSP2-4.5 and SSP5-8.5 scenarios were used. Three climate conditions were considered: i) Pr and PET with climate change, ii) only Pr with climate change, and iii) only PET with climate change, to estimate SPEI. Each climate condition was built using GCM trends over either Pr, PET or both that were incorporated into a stochastic generator. Results show that PET dominate changes in cities between 29°-35°S, while Pr is the dominant variable in cities between 35°-42°S. The methodology developed has shown to detect the dominant climate variable (precipitation or temperature) that will cause drought in the future.

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