Drought in Portugal: Current regime, comparison of indices and impacts on extreme wildfires.

Sci Total Environ

Centre for Research and Technology of Agro-Environment and Biological Sciences, CITAB, University of Trás-os-Montes and Alto Douro, Portugal; Instituto Dom Luiz, IDL, University of Lisbon, Lisbon, Portugal. Electronic address:

Published: October 2019

AI Article Synopsis

  • Drought is a significant climatic issue in Portugal, with increased risk of wildfires expected due to rising drought intensity and duration.
  • The study analyzed drought patterns from 1981 to 2017 using multiple indices (SPI, SPEI, RDI, VCI) and found that 67% of the months in this period were drought months.
  • A strong correlation was discovered between drought conditions and large wildfires, with most wildfires occurring during droughts, underscoring the important relationship between drought severity and fire incidence.

Article Abstract

In Portugal, drought characterizes the climatic variability, contributes to the increase of fire risk and its duration and intensity are expected to increase in future climate. Surprisingly, the quantitative and objective analysis to characterize the drought regime in current climate conditions as well as its influence on the occurrence of large wildfires (LW) has never been done for Portugal, which are the main objectives of this study. We assessed drought regime for recent past climate conditions (1981-2017), using four different drought indices, namely SPI, SPEI, RDI and VCI, and assessed the influence of drought in LW occurrence. Results include the characterization of drought number, duration, severity, intensity, extension, intra- and inter-annual variability for different classes of severity and the space-time distribution of LW in drought periods and affected area. Our main findings include 67% of the study period were drought months; regions with higher drought duration and severity assessed with SPI and SPEI for general drought conditions evolves from north to south with the increase of drought assessment period; drought characteristics present low intra - annual and inter - annual variability but are clearly associated to the temporal and spatial distribution of LW. In fact, all LW occurred during drought assessed with SPI or SPEI, almost all LW (97% to 95%) and corresponding burnt area (98% to 97%) occurred during drought assessed with SPI and SPEI. The relationship between drought and fire incidence is statistical significant for 3 - month SPI, 3 - and 6 - month SPEI, and is particularly strong for Moderate and Severe drought. 85% and 87% of LW occurred in area affected by drought assessed with SPI or SPEI, respectively. It is not clear which is the best index, but drought plays a fundamental role in the occurrence of large wildfires in Portugal.

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http://dx.doi.org/10.1016/j.scitotenv.2019.05.298DOI Listing

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