2025/01/14 by Patrick C. Murphy, Clifford F. Mass · 1 voice
Environmental Science · #Fire effects on ecosystems #Flood Risk Assessment and Management #Landslides and related hazards
paper · doi:10.1175/waf-d-24-0025.1
Abstract California is vulnerable to large, rapidly growing wildfires that can threaten human lives and damage physical infrastructure. This study analyzes the daily growth of all satellite-observed California fires from 2003 through 2020 and relates that growth to local meteorological and environmental conditions. Fire growth is defined using both absolute and relative metrics (absolute growth—the daily burned area; relative growth—the daily percent increase in burned area). Near-surface environmental conditions are evaluated before, during, and after periods of fire growth for individual fires of varying sizes and spread rates across events with both high and low relative growth. Regional spatial patterns and distributions of near-surface dryness and winds during large absolute-growth events are examined and compared to climatological conditions. Overall, large absolute-growth events generally occur when dead fuels are driest, trailing short periods of increased atmospheric dryness. For large absolute-growth events, high relative growth is usually associated with strong winds, while low relative growth is generally associated with quiescent climatological winds. Winds during high-relative-growth events are greatest in autumn, surpassing the 95th percentile on average. For these autumnal events, atmospheric dryness is less than during other seasons, but atmospheric and fuel dryness is still sufficient for fire. Irrespective of the season, winds during particularly rapid-growth events (high absolute and relative growth) are frequently downslope and influenced by local terrain regardless of the climatological conditions. Significance Statement Wildfires that undergo rapid growth are particularly dangerous to human life and infrastructure. This research finds that, given sufficient dryness, wind is the most important environmental factor in differentiating fire growth of varying sizes and spread rates and for enabling explosive wildfire growth.