Fire-weather conditions during two fires in Southern Portugal: Meteorology, Orography, and Fuel Characteristics

Abstract

The interactions between meteorology, orography and fuel have a major impact on fire dynamics, influencing its behaviour. This study presents the results about the atmospheric environment and surface aspects of two wildfires that occurred in Southern Portugal. Two numerical simulations were performed by the Meso-NH atmospheric model using a two-way nested domain configuration with horizontal resolutions of 2500 m and 500 m, respectively. Furthermore, observations of land use/land cover and live fuel moisture content analysis for each wildfire were used to understand the land occupation and vegetation dynamics. Both cases present significant fuel variability with low live fuel moisture content, showing high probability of fire occurrence over the region. The analysis of Castro Marim’s fire with ignition during the nighttime, presented critical fire weather conditions, namely high air temperatures and low relative humidity, even overnight. Furthermore, the interaction of the northerly flow with the local terrain led to the spread of the fire to southeast and south westward. In the second case study, Odemira’s fire exhibited a complex environment marked by continual shifts in wind direction. However, the study highlights the strong southeasterly flow prevailing from the Gibraltar Strait reaching the Algarve region and producing intense winds in the local mountains. Algarve region contains forest species such as maritime pine and eucalyptus in large variations of altitude that are highly susceptible to the occurrence of wildfires if the forests are not adequately manage, significantly threatening the safety of front-line firefighters. In a regional context, the present study shows that the use of atmospheric modelling can be useful in assessing fire risk when also the surface aspects obtained from remote sensing observations are considered.