Fire danger indices derived from NOAA-AVHRR images: a comparison and interpretation using meteorological variables

摘要

In this paper four indices suitable to estimate fire danger due to vegetation water stress are studied. These indices are calculated and analysed by combining NOAA-AVHRR images, received and processed daily in our Remote Sensing Laboratory, and meteorological data. Precipitation and air temperature, recorded by the Spanish Meteorological Service (INM), are interpolated into the spatial resolution of the AVHRR images. Solar radiation derived from Meteosat images has also been used. The first two danger indices are based on the analysis of the NDVI temporal evolution, its decrease is supposed to be related to an increase in water stress and, consequently, in fire danger. The other two indicators are calculated using surface temperature, derived fromthe AVHRR thermal channels, air temperature and the NDVI and are thought to be related to evapotranspiration or hydric stress. The indices are calculated, tested (using ground data generated by the Spanish Forestry Service), compared and analysed by means of their relation with meteorological variables. Three of them can be used operationally and they are calculated on a daily basis in our Laboratory and sent to the Spanish Forestry Service during months of risk within the framework of an agreement developed over the last four years.