Identification of favourable local-scale weather forcing conditions to Iberia’s largest fires

The Mediterranean region is characterized by frequent summer wildfires, which represent an environmental and socioeconomic burden [1]. Some Mediterranean countries (or provinces) are particularly prone to Large Fires (LF), namely Portugal, Galicia (Spain), Greece, and southern France [1,2]. Moreover, the Mediterranean basin corresponds to a major hotspot of climate change, and anthropogenic warming is expected to increase the total burned area due to wildfires in Iberian Peninsula (IP) [3].

Here, we propose to classify summer LF (June-September) for fifty-four provinces of the IIP according to their local-scale weather conditions (i.e. temperature, relative humidity, wind speed) and to fire danger weather conditions as measured by two fire weather indices (Duff Moisture Code and Drought Code). A cluster analysis was applied to identify a limited set of Fire Weather Types (FWT), each characterized by a combination of meteorological conditions leading to a better understanding of the relationship between meteorological drivers and fire occurrence. For each of the provinces, two significant FWT were identified with different characteristics, one dominated by high positive temperature anomalies and negative humidity anomalies (FWT1), and the other by intense zonal wind anomalies (FWT2) with two distinct subtypes in Iberia (FWT2_E and FWT2_W). Consequently, three distinct regions in the IP are identified: 1) dominated by FWT1, which is responsible for the largest amount of area burned in most of central-West provinces of Iberia; 2) the regions where the FWT2_E, associated with east winds is predominant, which are concentrated in the Northwest regions of the IP and the 3) regions where second subtype dominates, related with west winds (FWT2_W) in the easternmost provinces of the peninsula. Additionally, it was possible to verify that for each of the three regions the influence of the variables under study varies at different timescales. We reinforce the importance of studying the problem associated with LF for regions where similar conditions were verified regardless national borders.

 

[1] Trigo, R. M., Sousa, P. M., Pereira, M. G., Rasilla, D., & Gouveia, C. M. (2013). “Modelling wildfire activity in Iberia with different atmospheric circulation weather types”. International Journal of Climatology 36(7), 2761–2778. https://doi.org/10.1002/joc.3749.

[2] Ruffault, J., Moron, V., Trigo, R. M., & Curt, T. (2016). “Objective identification of multiple large fire climatologies: An application to a Mediterranean ecosystem”. Environmental Research Letters 11(7). https://doi.org/10.1088/1748-9326/11/7/075006.

[3] Sousa, P. M., Trigo, R. M., Pereira, M. G., Bedia, J., & Gutiérrez, J. M. (2015).”Different approaches to model future burnt area in the Iberian Peninsula”. Agricultural and Forest Meteorology 202, 11–25. https://doi.org/10.1016/j.agrformet.2014.11.018.

 

Acknowledgements: This work was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project IMPECAF (PTDC/CTA-CLI/28902/2017). The authors also thank Miguel M. Pinto for extracting the ERA-Interim reanalysis, the MSG and the FWI data used in this study.