Suchergebnisse

Abstract. Historical fire records and meteorological observations spanning over one century (1894–2010) were assembled in a database to collect long-term fire and weather data in Greece. Positive/negative events of fire occurrence on an annual basis were considered as the years where the annual values of the examined parameters were above (positive values) or below (negative values) the 95% confidence limits around the trend line of the corresponding parameter. To analyse the association of positive/negative events of fire occurrence with meteorological extremes, we proceeded with a cross-tabulation analysis based on a Monte Carlo randomization. Positive/negative values of total annual precipitation were randomly associated with the corresponding values of burned areas, and significant associations were observed for seasonal precipitation totals (spring and fire season). Fire season precipitation is the dominant factor coinciding with negative values of area burned, while years with high spring precipitation coincide with years with large areas burned. These results demonstrate the dual role of precipitation in controlling a fire's extent through fuel build-up and dryness. Additionally, there is a clear outperformance of precipitation-related variables compared with temperature-related weather revealing that, at least in Greece, total area burned at the national scale is controlled by precipitation totals rather than air temperature. This analysis improves our understanding of the underlying mechanisms of fire regimes and provides valuable information concerning the development of models relating fire activity to weather parameters, which are essential when facing a changing climate that may be associated with shifts in various aspects of the typical fire regimes of ecosystems. Our results may allow fire managers to more easily incorporate the effect of extreme weather conditions into long-term planning strategies. They contribute to the exploration of fire–climate relationships and may become more important if climate change scenarios are used to predict the occurrence of future extreme weather taking into consideration that climate change is discussed on the basis of changes of extremes rather than changes in means.

Abstract. Understanding how fire weather danger indices changed in the past and how such changes affected forest fire activity is important in a changing climate. We used the Canadian Fire Weather Index (FWI), calculated from two reanalysis data sets, ERA-40 and ERA Interim, to examine the temporal variation of forest fire danger in Europe in 1960–2012. Additionally, we used national forest fire statistics from Greece, Spain and Finland to examine the relationship between fire danger and fires. There is no obvious trend in fire danger for the time period covered by ERA-40 (1960–1999), whereas for the period 1980–2012 covered by ERA Interim, the mean FWI shows an increasing trend for southern and eastern Europe which is significant at the 99% confidence level. The cross correlations calculated at the national level in Greece, Spain and Finland between total area burned and mean FWI of the current season is of the order of 0.6, demonstrating the extent to which the current fire-season weather can explain forest fires. To summarize, fire risk is multifaceted, and while climate is a major determinant, other factors can contribute to it, either positively or negatively.