Index sensitivity analysis applied to the Canadian Forest Fire Weather Index and the McArthur Forest Fire Danger Index

Abstract

ABSTRACT:A number of different methodologies are developed for examining the sensitivities of an index. These methodologies are applied to examine the characteristics of the Canadian Fire Weather Index (FWI) and the McArthur Forest Fire Danger Index (FFDI) using 8 years of gridded data throughout Australia. Percentile changes in input conditions show that the indices are similar to each other in that they are both most sensitive to wind speed, then secondly to relative humidity and thirdly to temperature. On a finer scale, a combination of the relationship between the indices and their partial derivatives shows that the FFDI is relatively less sensitive to wind speed and rainfall, and more sensitive to temperature and relative humidity, than the FWI. A method based on equilibrium values of the indices shows that the FFDI has a temperature threshold set by recent rainfall above which its sensitivity increases, resulting in some non-linearity in its relationship with the FWI. The sensitivity differences between the indices mean that the indices are complementary in that they each respond to a somewhat different set of conditions, as is shown by examining a number of recent fire events. The fire events also reveal that index values associated with dangerous fire behaviour can vary greatly between different regions. Methods to reduce the consequences of this variation are examined, including the use of index percentiles.

Fuel moisture sensitivity to temperature and precipitation: climate change implications

“…As temperature goes up typically relative humidity goes down and this decreased humidity would further increase the drying rate and decrease equilibrium moisture levels, and thus lead to an overall increase in fuel drying. Indeed sensitivity studies on weather inputs and outputs of the FWI System have shown there to be strong influence of relative humidity (Dowdy et al 2010). We chose not to modify relative humidity in our temperature scenarios to provide a simpler albeit more conservative presentation of the amount of drying that might occur with increased temperatures.…”

Extreme drying events in the Australian high-country and their implications for bushfire risk management

“…However, we also note the role of wind speed in driving the elevated fire danger index values in the high-country in some instances, for example the event that occurred in the early morning of 29 November 2006. Fire danger indices are sensitive to changes in both wind speed and humidity and processes that cause large changes in both can have a significant effect on fire danger levels (Matthews 2008;Dowdy et al 2010;Bedia et al 2012).…”

Probabilistic prediction of wildfire economic losses to housing in Cyprus using Bayesian network analysis

“…Which of the two should be used depends on the vegetation type (forest, shrub, grass). Here, FFDI or FGDI are adapted to the FWI according to Dowdy et al (2010). Time for ground attack and Air time are the time needed by ground and air suppression crews to reach the fire.…”