Modelling the meteorological conditions during the occurrence of mega fires in Portugal

Abstract

The extensive study of wildfires is crucial to better understand how fire may be influenced by the atmospheric conditions. The study explores the meteorological conditions associated with the mega fires occurred in Portugal on 15 October 2017. On that day, more than 500 fires were active in Portugal with tens of thousands of burned area and 48 fatalities. The MesoNH model can represent the atmospheric motions in different scales and was configured in different resolutions aiming to investigate the events in different temporal and spatial scales. For example, aiming to represent the synoptic conditions, the model was configured in a large domain (300×250 grid points) and 15 km resolution. In the small scale, the model was coupled to a fire propagation model (ForeFire) and configured into three nested domains (300×300 grid points) with horizontal resolutions of 2000 m, 400 m and 80 m. In this simulation, the Quiaios wildfire was considered. The results highlight the importance of the use of cloud resolving models with very-high spatial and temporal resolutions for representing the development of the pyro-convective phenomena, namely the PyroCu clouds development. Also, this experiment at higher resolution showed the generation of intense gusts in Portugal. In the large-scale context, the simulation well represented the evolution of the hurricane Ophelia near Portugal, indicating the important role played by the weather system inducing strong south-westerly winds over Portugal in the late afternoon of 15 October. Therefore, the passage of the hurricane Ophelia along the Portuguese coast on the 15th of October brought strong winds to Portugal that helped in the rapid spread of the fires and large burned areas.