The Role of Atmospheric Circulation in Favouring Forest Fires in the Extreme Southern Portugal

The study explores two forest fires in extreme southern Portugal aiming to increase the knowledge of how atmospheric circulation influenced the fire dynamics in each event. The meteorological conditions were simulated by the Meso-NH full-physics non-hydrostatic limited-area research model. The two numerical simulations were performed using a two-way nested domain configuration with horizontal resolutions of 2500 m and 500 m. In both cases, the large-scale atmospheric environment was marked by the Azores Anticyclone west of Portugal which induced northerly winds over the coastal of Mainland Portugal. The analysis of Tavira's fire (18-21 July 2012, 24,800 ha of total burned area) revealed flow characteristics resembling a low-level jet located below 1 km, with stronger winds during the second day resulting in enhanced fire spread rates. The second case study (Aljezur, 19-21 June 2020; 2302 ha of burned area) highlights a fire occurring under atypical fire weather conditions, namely lower air temperature and higher relative humidity; however, orographic effects produced downslope winds favouring fire propagation. This study provides a better understanding of the fire critical conditions in extreme South Portugal and investigates the atmosphere-orography interactions in the region that played an important role in the development of these two forest fires. Increasing knowledge about large fires in Southern Portugal can support fire management practices and encourage the sustainable development of the region.