A Semi-Simple Approach for Estimating Fire Season Length

Developing a method for estimating fire season length using well known metrics is useful for understanding yearly changes in the onset and ending of fire season and the factors which may influence such changes. Southern California Edison’s (SCE) Fire Science team used the Energy Release Component (ERC) to estimate the length of fire season across Southern California using SCE’s historical gridded data set, spanning the years 1980 to 2022. This 2 km by 2 km data set contains all the National Fire Danger Rating System (NFDRS) indices at an hourly temporal resolution. To demonstrate our approach, a subsection of Southern California was selected where daily historical values of the spatially averaged 90^th percentile ERC were merged with historical fire ignitions to establish a critical ERC threshold level. Fire season length was then determined by summing up the number of consecutive days above this threshold for each year within SCE’s historical data set. A step-by-step process illustrating this methodology and the resulting output will be presented. Future studies will explore whether fire season beginning and end dates can be predicted months ahead using standard meteorological variables and/or teleconnection indices.