Synoptic patterns favouring lightning-ignited wildfires in Catalonia

Wildfires cause substantial losses to socio-economic and natural assets, especially in Mediterranean-climate regions. Despite human activity is the main cause of wildfires in Mediterranean European countries, lightning-ignited wildfires should be also considered a major disruptive agent as they can trigger large fires. Besides, recent studies on the potential climate change effects on wildfires pointed out that lightning-ignited wildfires may gain relevance in Mediterranean areas in the years to come.

In this regard, the present study analyses the meteorological conditions favouring lightning-ignited wildfires in Catalonia (NE Iberian Peninsula). Gaining insight into circulation types favouring thunderstorms that ignite wildfires can be useful in the forest protection tactical decision-making process, i.e. locating ignitions and potential holdover fires, preparing for days with multiple ignitions or routing detection flight paths.

It is worth noticing that one of the reasons why lightning-caused wildfires are difficult to manage is that they can survive for several days before flaring up. That is, even if forest fuels remain damp after the thunderstorm’ rainfall, lightning ignitions may survive smouldering underneath, emerging days later as surface vegetation becomes dry enough to support sustained combustion.

For this reason, on a first step, a reliable lightning-wildfire association is needed to properly identify the date and time of the firestarter for each wildfire. Afterwards, the circulation types on the days of ignition are analysed.

The study relies on a dataset of more than 750 lightning-ignited wildfires, gathered by the Forest Protection Agency of the autonomous government of Catalonia between 2005 and 2018. Lightning data comes from the Lightning Location System operated by the Meteorological Service of Catalonia.