Wildfires in the Euro-Mediterranean region: links with meteorological processes

Abstract : The question this thesis stems from is: ”To which extent weather controls the life cycle of forest fires in the Mediterranean?”. The analysis developed here is based on remotely-sensed fire data, meteorological reanalyses and numerical simulations. A large part of the thesis work focused on the impact of weather on wildfires. First I showed that weather controls the life cycle of forest fires very tightly when these fires are large enough. Many factors are crucial: the strength of the heatwave, the precipitation deficit in month preceding the summer season and finally wind speed. The relationship between fire size and wind was found very atypical by comparison with other regions (Asia, Central Europe). The largest burned areas are observed for either low wind speeds or high wind situations, with a minimum for moderate winds. This counter- intuitive behavior is observed solely during heatwaves. The causes of these different types or fire/wind relationships were identified. These results allowed to build the foundations of a statistical modeling framework that can be used to forecast not just fire risk but also the distribution of fire size and intensity. This step towards forecasting is innovative and much more informative than fire risk modeled currently used. A second part was written about on the impact of fires on local weather. I designed a numerical sensibility study of the August 2003 Portugal fire event. In this study, I showed the triggering of inland breezes over the burned areas strengthening convection. I studied the sensibility of this phenomenon with respect to the dynamical and land-use resolution in the model. Finally I showed that burned area were favorable to increased cloudiness with an effect of increased precipitation risk (even if the precipitation signal stays very weak over the unique studied month).
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Charles Hernandez. Wildfires in the Euro-Mediterranean region: links with meteorological processes. Geophysics [physics.geo-ph]. Ecole Doctorale de l'Ecole Polytechnique, 2015. English. ⟨tel-01284599⟩

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