UC Santa Barbara

Annual area burned has increased in California over the past three decades as a result of rising temperatures and a greater atmospheric demand for moisture, a trend that is projected to continue throughout the 21st century as a result of climate change. However, the impacts of climate on the size, severity, and seasonality of wildfire activity are strongly influenced by ecosystem, predominant vegetation types, weather patterns, topography, and human activity. The individual wildfire burned perimeter and ecoregion-level spatial scales adopted for this research increases the amount of local information, as well as the resolution with which fire and land managers can implement strategies and counter measures when addressing issues related to climate change. This research combines 18 years of wildfire burned area perimeter maps, high resolution land surface modeling, a suite of remote sensing datasets, and nearly a century of statistically downscaled climatological data in an effort to quantify the impact of wildfire on local meteorology, as well as the influence of climate change on extreme fire weather. This dissertation investigates the bi-directional climate-wildfire feedback system in California through a detailed examination of the impacts of wildfire on the surface energy balance, an assessment of the influence of wildfire burn severity on the five-year postfire trajectory of three biophysical variables, and the quantification of the impacts of climate change on extreme fire weather. Results indicate that the largest changes to net radiation in the four months following ignition were primarily caused by decreases in latent heat flux following wildfire-induced vegetation removal. This vegetation removal, coupled with the lowering of albedo from ash deposition, also contributed to decreases in sensible heat flux. Further, vegetation abundance and land surface temperature did not return to prefire levels, for any burn severity class, after five years. Lastly, this work provides evidence that fire weather conditions conducive to large wildfires will become more extreme and extend later into the fall season in most areas of California by 2100. The methods of investigation used here may be applied to other regions of the world in an effort to inform the mitigation and suppression of large wildfires.