Abstract
Research Highlights: Flammability of wildland fuels is a key factor influencing risk-based decisions related to preparedness, response, and safety in Alaska. However, without effective measures of current and expected flammability, the expected likelihood of active and problematic wildfires in the future is difficult to assess and prepare for. This study evaluates the effectiveness of diverse indices to capture high-risk fires. Indicators of drought and atmospheric drivers are assessed along with the operational Canadian Forest Fire Danger Rating System (CFFDRS). Background and Objectives: In this study, 13 different indicators of atmospheric conditions, fuel moisture, and flammability are compared to determine how effective each is at identifying thresholds and trends for significant wildfire activity. Materials and Methods: Flammability indices are compared with remote sensing characterizations that identify where and when fire activity has occurred. Results: Among these flammability indicators, conventional tools calibrated to wildfire thresholds (Duff Moisture Code (DMC) and Buildup Index (BUI)), as well as measures of atmospheric forcing (Vapor Pressure Deficit (VPD)), performed best at representing the conditions favoring initiation and size of significant wildfire events. Conventional assessments of seasonal severity and overall landscape flammability using DMC and BUI can be continued with confidence. Fire models that incorporate BUI in overall fire potential and fire behavior assessments are likely to produce effective results throughout boreal landscapes in Alaska. One novel result is the effectiveness of VPD throughout the state, making it a potential alternative to FFMC among the short-lag/1-day indices. Conclusions: This study demonstrates the societal value of research that joins new academic research results with operational needs. Developing the framework to do this more effectively will bring science to action with a shorter lag time, which is critical as we face growing challenges from a changing climate.
Highlights
Boreal fires are necessary for a healthy ecosystem yet a hazard to humans when uncontrolled [1].Wildland fires in Alaska are characterized by a relatively small number of large wildfires ignited by lightning in remote areas [2]
Significant wildfire occurrence and growth in Alaska are on the rise, results here show that the set of long-lag drought indices (e.g., Drought Code (DC), Evaporative Demand Drought Index (EDDI) 52-day, Standardized Precipitation Evapotranspiration Index (SPEI) 52-day) were generally the poorest performers throughout our analysis, possibly reflecting the fact that extended droughts have not typically impacted large portions of the state on a year-to-year basis
Based poorest performers throughout our analysis, possibly reflecting the fact that extended droughts have on our results, we can conclude that Duff Moisture Code (DMC) and Buildup Index (BUI), which are operationally used by the Alaska fire not typically impacted large portions of the state on a year-to-year basis
Summary
Wildland fires in Alaska are characterized by a relatively small number of large wildfires ignited by lightning in remote areas [2]. This results in large year-to-year variability in area burned, dominated by individual years with extremely large totals. The number of years where total area burned exceeds statistical norms has increased in frequency and impact in recent years [3]. The vast boreal forests, with stand-replacing crown fires, dominate both the ecological backdrop and impact of wildfires in Alaska, though wildfire effects in Arctic tundra appear to be increasing as well [8,9]
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