Performance of a newly developed integrated fire rating index in Sardinia, Italy

Although fire danger models are calibrated for specific geographic areas, they are often used outside of the calibration area. In addition, no stardardized statistical procedures have been used for the evaluation of fire danger models. In this paper, the performance of an integrated fire rating index (Ichnusa Fire Index, IFI), developed using wildfire data from Sardinia, Italy, is presented. Depending on the sampling rate, IFI computation requires meteorological, micrometeorological, topological and ecophysiological data. The IFI index includes four codes - i) the Drought Code (DC), ii) the Meteo Code (MC), iii) the Fuel Code (FC), and iv) the Topological Code (TC) - that are related to i) water status of plants, ii) turbulence or weather conditions, iii) density and moisture of vegetation, and iv) orography, slope and site exposure, respectively. To determine FC values, the definition of fuel categories is needed. Based on a vegetation cover map of Sardinia, six fuel types were described as (1) broad leaf forest, (2) cork oak forest, (3) short shrubland, (4) tall shrubland, (5) garigue, and (6) grassland. IFI was calculated for the period 2000-2004 using data from the meteorological network of the Agrometeorological Service of Sardinia and the index values were compared with the statistics on fire events occurred during the same period. A very good relationship was found between index values, number and burned surfaces. IFI was also compared with three commonly used fire danger indices [i.e., Canadian Fire Weather Index (FWI), Portuguese Index (Port), and Italian Meteorological Danger Index (IMPI)]. All fire events occurred during the 2002-2004 period were included in the analysis. The predictive capability of each index was evaluated determining its ability to discriminate days with or without fire events using the Mahalanobis distance (DM) test and the Scores 1, 2 and 3 described by Mandallaz and Ye (1996). IFI showed the highest Mahalanobis distance test, indicating better results when compared with FWI, Port and IMPI. Also, Scores 1, 2 and 3 confirmed the good performance of IFI in comparison with the other indices. The IFI index was also evaluated using weather forecasts obtained from a limited area forecast model (BOLAM) for the period 2005-2006. Our results indicate the promising capability of IFI to give acceptable forecasts of fire events in Sardinia.