A comparison of hourly fine fuel moisture code calculations within Canada

This paper compares approaches to calculating hourly values of the fine fuel moisture code (FFMC) used in Canada. The equations used in the daily FFMC calculations within the Canadian Forest Fire Weather Index (FWI) System are explained and compared to those used in the hourly calculations developed by Van Wagner (1977). An alternate approach using just the equilibrium moisture content (EMC) is introduced. A third approach developed by Lawson et al. (1996) provides diurnal adjustments for the FFMC based strictly on the standard noon FFMC and expected diurnal variation. Hourly FFMC and EMC values are tested to see if either routine approaches observed variations as interpreted from Lawson et al. Finally, results from fire-growth simulations are used to assess the impact of the methods.