Meteorological environments leading to two large fires in Southern Portugal

Abstract

The study is a step forward in the characterization of meteorological environments that favour the evolution of large and extreme fires in Southern Portugal. The region has some fire-prone areas which are recognized by the mega fires occurred in 2003, 2005, and 2018. Two numerical simulations were performed using the Meso-NH non-hydrostatic research model and used to investigate in detail the atmospheric environments of two large fires that occurred on 18th July 2012 and 19th June 2020. The simulations were configured using two nested domains with a 375 km × 375 km grid domain (D1) at 2.5 km horizontal resolution and a 150 km × 150 km domain (D2) at 500 m resolution added before the start of the fires. The vertical grid was configured with 50 stretched levels following the terrain. The initial and boundary conditions are provided by the 6-hourly operational ECMWF analyses. The large-scale circulation has been characterised using data obtained from the ECMWF's Meteorological Archival and Retrieval System. In addition to the large-scale circulation, namely the positioning of the Azores anticyclone and the thermal low development over the Iberian Peninsula, the results have shown the important role played by regional orography in creating favourable fire weather conditions. For instance, the high-resolution simulations showed the high daytime temperatures and sometimes overnight, low humidity, and strong wind gusts that favour fire spread. In July 2012, the typical sea breeze circulation affected the fire evolution, whereas the intense downslope winds favoured the fire spread in June 2020. The study brings useful guidelines for interpreting the impact of different mesoscale environments that may produce large fires, namely the orographic effects that can increase the fire susceptibility and vulnerability of some regions. This study was funded by national funds through FCT-Foundation for Science and Technology, I.P. under the PyroC.pt project (Ref. PCIF/MPG/0175/2019).