This work was supported by NASA awards 80NSSC21K1603 (DAK and DS) and 80NSSC21K1501 (PCL), and by NSF award OAI-2019762 (JTA).
Geophysical Research Letters
Wildfires -- research, Wildfire risk -- United States
Cloud-to-ground lightning with minimal rainfall (“dry” lightning) is a major wildfire ignition source in the western United States (WUS). Although dry lightning is commonly defined as occurring with <2.5 mm of daily-accumulated precipitation, a rigorous quantification of precipitation amounts concurrent with lightning-ignited wildfires (LIWs) is lacking. We combine wildfire, lightning and precipitation data sets to quantify these ignition precipitation amounts across ecoprovinces of the WUS. The median precipitation for all LIWs is 2.8 mm but varies with vegetation and fire characteristics. “Holdover” fires not detected until 2–5 days following ignition occur with significantly higher precipitation (5.1 mm) compared to fires detected promptly after ignition (2.5 mm), and with cooler and wetter environmental conditions. Further, there is substantial variation in precipitation associated with promptly-detected (1.7–4.6 mm) and holdover (3.0–7.7 mm) fires across ecoprovinces. Consequently, the widely-used 2.5 mm threshold does not fully capture lightning ignition risk and incorporating ecoprovince-specific precipitation amounts would better inform WUS wildfire prediction and management.
Copyright (c) 2023 The Authors
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Kalashnikov, D. A., Abatzoglou, J. T., Loikith, P. C., Nauslar, N. J., Bekris, Y., & Singh, D. (2023). Lightning‐Ignited Wildfires in the Western United States: Ignition Precipitation and Associated Environmental Conditions. Geophysical Research Letters, 50(16), e2023GL103785.