Climatology of the stability and humidity terms in the Haines Index to improve the estimate of forest fire risk in the Western Mediterranean Basin (Valencia region, Spain)

Abstract

The stability and moisture content of the different atmospheric levels are commonly used to assess the risk index in the propagation and evolution of a hypothetical forest fire. The Haines Index (HI) combines these terms to determine the environmental potential for wildfire growth. In this paper the environmental stability and humidity associated with the lower atmospheric layers in the Western Mediterranean Basin are investigated by analysing HI calculations over a 29-year period. The HI climatology can be applied to the study of plume-dominated forest fires. These fires tend to present very erratic propagation behaviour and create highly dangerous situations for fire brigades. Thus the knowledge of the typical index values and the meteorological situations that generate them could be extremely useful for minimizing the fire risk and planning specific fire-fighting activities. In this study we carry out a spatial and temporal analysis of the Index and its terms in the Valencia region on the basis of NCEP/NCAR reanalysis data from 1980 to 2008, obtaining a detailed climatological analysis of the HI in the Valencia region for each variant of elevation, which can be used as a reference tool. Moreover, using NCEP reanalysis maps at 500 and 850 hPa, we also perform a daily synoptic analysis for the studied period which is finally associated to the different values that the Index can show in this area. As a result three dominant synoptic weather situations have been defined in this region: continental, maritime and convective. A direct proportionality has been found between increases in the HI and convective situations.