KBDI as an Indicator of
Potential Wildfire Activity

The next step in determining potential threshold values is to develop a definition of above average fire activity and drought conditions. Average values alone are not enough as the averages vary by month so it is difficult to establish definitions that are consistent month to month. If the monthly mean is subtracted from the data to produce anomalies and then this value is normalized by the standard deviation of that mean, all data is then referenced to a common scale. On this common scale, mean conditions are represented by a value of zero.

Figure 1 shows above average fire seasons from 1981-1998. Significant fire seasons (1985, 1989, etc.) are clearly evident in this figure. Significant fire seasons are identified as having normalized values in excess of 1.0 which represents an average of 24,000 acres above normal.

Figure 1: Normalized fire activity for 1981 - 1998

Significant levels of drought are determined by normalizing the KBDI in a similar manner as to the fire activity. Thirty-five years of data are used in determining the mean and standard deviation of the KBDI on a daily basis (Figure 2). The threshold values of KBDI are determined by comparing the drought to the fire activity.

Figure 2: Normalized KBDI for 1981-1998. Values greater than 1.0 are coincident with above normal fire activity.

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