Assessing the role played by meteorological conditions on the interannual variability of fire activity in four subregions of Iberia

Abstract

The Iberian Peninsula is recurrently affected by severe wildfires resulting from an interplay of human activities, landscape features, and atmospheric conditions. Here we assess the role played by atmospheric conditions on wildfire activity as measured by Fire Radiative Power (FRP) derived from observations by the MODIS instrument. The study spans the period 2001-2020 and is performed in four pyroregions covering the Iberian Peninsula that have been used in recent years, namely the northwest (NW), southwest (SW), north (N) and east (E). Atmospheric conditions are characterized by means of the Fire Weather Index (FWI), which rates fire intensity. For each pyrogegion, the distribution of log_10⁡FRP is characterized by means of a statistical model that combines a truncated lognormal distribution central body with a lower and an upper tail, both consisting of Generalized Pareto (GP) distributions. The model is then improved by using FWI as a covariate of the parameters of the lognormal and the two GP distributions. Then, for each pyroregion, a set of 100 synthetic time series of total annual FRP is set up using the statistical models with and without FWI as a covariate. The role played by meteorological conditions is finally assessed by comparing the two sets between each other and against the time series of annual FRP derived from observations by the MODIS instrument. Results obtained for region SW show an increase from 90% to 96% of interannual explained variance of FRP when progressing from the model without to the model with FWI as covariate. Increases from 95% to 96%, 84% to 90% and from 78% to 86% were obtained for regions NW, N and E. It is worth stressing that these are conservative estimates of change, since the dependence of number of ignitions on FWI was not taken into account.