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- Title
Response of Land Surface Albedo to Fire Disturbance in the Sierra Nevada Seasonal Snow Zone Over the MODIS Record.
- Authors
Gayler, J. M.; Skiles, S. M.
- Abstract
Wildfires in the snow zone can brighten winter and spring landscapes by removing forest canopy, revealing underlying snow cover. Land surface albedo (LSA) alterations associated with transitioning from a canopied, snow‐hiding vegetation regime to a snow‐revealing landscape have impacts on the surface energy balance, with implications for climate and water supply. Forest fires are increasing in frequency, size, and elevation, but the change in LSA due to fire in the seasonal snow zone (SSZ) is poorly understood. This study addresses this knowledge gap for the Sierra Nevada, where recent climatic changes have contributed to droughts, earlier and more rapidly declining snowpacks, and worsening wildfire impacts. Remotely sensed snow fraction and LSA data from Moderate Resolution Imaging Spectrometer were used to assess the impact of wildfire on landscapes in the Sierra Nevada SSZ by comparing LSA in burn scars to unburned control areas and the historical average LSA, then quantifying the surface radiative forcing (RF) associated with change in LSA. Among high and moderate burn severity fires, winter LSA varied depending on snow cover, land characteristics, and burn severity, ranging from 0.12 in low‐snow fire scars to 0.47 in snow‐covered fire scars. This study adds to understanding of how landscapes respond to wildfires and the subsequent impacts on the surface energy balance. Plain Language Summary: Wildfires alter how the landscape absorbs and reflects sunlight by removing forest canopy and exposing the underlying ground surface, leading to changes in surface temperature. This impact is particularly pronounced in areas that are snow‐covered due to the brightness of snow contrasted with dark canopy. As wildfires become more frequent, intense, and larger, it is crucial to understand how they affect seasonally snow‐covered landscapes. This study focuses on the Sierra Nevada, CA, where recent climate changes have led to more droughts, earlier melting of snow, and intensifying wildfire. We used satellite data to study how wildfires impact landscape reflectance by comparing burned areas to both nearby unburned areas and historical data. We found that great variability was present in landscape response but overall, in the first 4 years after a high or moderate severity wildfire, the snow‐covered areas were brighter in winter compared to unburned areas. Quantifying how absorption of sunlight changes following wildfire helps us understand how landscapes respond to wildfires and how they affect the local climate. Key Points: Land surface albedo response to fire in the Sierra Nevada seasonal snow zone varies with snow cover, land characteristics, and burn severityContrary to current understanding, post‐fire snow‐free dates were variable and not consistently earlier than in surrounding unburned areasFire‐induced albedo changes led to greater cooling effect (net negative radiative forcing) in moderate compared to high‐burn severity areas
- Subjects
SIERRA Nevada (Calif. &; Nev.); WILDFIRES; ALBEDO; DROUGHT management; SNOWMELT; SNOW cover; FOREST fires; RADIATIVE forcing; FUEL reduction (Wildfire prevention)
- Publication
Earth's Future, 2024, Vol 12, Issue 6, p1
- ISSN
2328-4277
- Publication type
Article
- DOI
10.1029/2023EF004172