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Abstract Coupled fire‐atmosphere models often struggle to simulate important fire processes like fire generated flows, deep flaming fronts, extreme updrafts, and stratospheric smoke injection during large wildfires. This study uses the coupled fire‐atmosphere model, WRF‐Fire, to examine the sensitivities of some of these phenomena to the modeled total fuel load and its consumption. Specifically, the 2020 Bear Fire and 2021 Caldor Fire in California's Sierra Nevada are simulated using three fuel loading scenarios (1X, 4X, and 8X LANDFIRE derived surface fuel), while controlling the fire rate of spread using observations. This approach helps isolate the fuel loading and consumption needed to produce fire‐generated winds and plume rise comparable to radar observations of these events. Increasing fuel loads and corresponding fire residence time in WRF‐Fire leads to deep plumes in excess of 10 km, strong vertical velocities of 40–45 m s−1, and combustion fronts several kilometers in width (in the along wind direction). These results indicate that LANDFIRE‐based surface fuel loads in WRF‐Fire likely under‐represent fuel loading, having significant implications for simulating landscape‐scale wildfire processes, associated impacts on spread, and fire‐atmosphere feedbacks.
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Observations of a rotating pyroconvective plume
BackgroundThere is an ongoing need for improved understanding of wildfire plume dynamics. AimsTo improve process-level understanding of wildfire plume dynamics including strong (>10 m s-1) fire-generated winds and pyrocumulus (pyroCu) development. MethodsKa-band Doppler radar and two Doppler lidars were used to quantify plume dynamics during a high-intensity prescribed fire and airborne laser scanning (ALS) to quantify the fuel consumption. Key resultsWe document the development of a strongly rotating (>10 m s-1) pyroCu-topped plume reaching 10 km. Plume rotation develops during merging of discrete plume elements and is characterised by inflow and rotational winds an order of magnitude stronger than the ambient flow. Deep pyroCu is initiated after a sequence of plume-deepening events that push the plume top above its condensation level. The pyroCu exhibits a strong central updraft (~35 m s-1) flanked by mechanically and evaporative forced downdrafts. The downdrafts do not reach the surface and have no impact on fire behaviour. ALS data show plume development is linked to large fuel consumption (~20 kg m-2). ConclusionsInteractions between discrete plume elements contributed to plume rotation and large fuel consumption led to strong updrafts triggering deep pyroCu. ImplicationsThese results identify conditions conducive to strong plume rotation and deep pyroCu initiation.
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- Award ID(s):
- 2114251
- PAR ID:
- 10643843
- Publisher / Repository:
- DOI PREFIX: 10.1071
- Date Published:
- Journal Name:
- International Journal of Wildland Fire
- Volume:
- 33
- Issue:
- 3
- ISSN:
- 1049-8001
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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