Since summer 1996 the forest fire index calculation in Finland is based on surface moisture estimation. The calculation is done on a 10*10 km grid. Air temperature, air humidity, wind speed , solar radiation and precipitation measurements made on observing stations are interpolated onto the grid with an objective interpolation method known as ‘kriging’. Potential evaporation is calculated for each grid-square based on the interpolated meteorological data using the Penman-Monteith-equation. The moisture of a 60 mm thick surface layer is estimated using potential evaporation and precipitation data, and finally, the surface moisture is scaled to forest-fire index values (1-6) which are sent to forest fire authorities through the World Wide Web. In the future the inclusion of weather radar and satellite information into the spatial analysing system will further improve spatial analyses of precipitation and solar radiation.
Source: Ari Venäläinen, and M.Heikinheimo. The Finnish Forest Fire Index Calculation System. In: Proceedings of the International IDNDR-Conference on Early Warning Systems for the Reduction of Natural Disaster EWC ’98, Potsdam, Germany, 7-11 September 1998, (in press.)