Abstract
Abstract. Almost USD 3 billion per year is appropriated for wildfire management on public land in the United States. Recent studies have suggested that ongoing climate change will lead to warmer and drier conditions in the western United States, with a consequent increase in the number and size of wildfires, yet large uncertainty exists in these projections. To assess the influence of future changes in climate and land cover on lightning-caused wildfires in the national forests and parks of the western United States and the consequences of these fires on air quality, we link a dynamic vegetation model that includes a process-based representation of fire (LPJ-LMfire) to a global chemical transport model (GEOS-Chem). Under a scenario of moderate future climate change (RCP4.5), increasing lightning-caused wildfire enhances the burden of smoke fine particulate matter (PM), with mass concentration increases of ∼53 % by the late 21st century during the fire season in the national forests and parks of the western United States. In a high-emissions scenario (RCP8.5), smoke PM concentrations double by 2100. RCP8.5 also shows enhanced lightning-caused fire activity, especially over forests in the northern states.
Highlights
Both the incidence and duration of large wildfires in the forests of the western United States have increased since the mid-1980s (Westerling et al, 2006; Abatzoglou and Williams, 2016), affecting surface levels of particulate matter (Val Martin et al, 2006, 2015), with consequences for human health (Liu et al, 2017) and visibility (Spracklen et al, 2009; Ford et al, 2018)
Combined with emission factors from Akagi et al (2011), dry matter burned calculated by LPJ-LMfire can be used to estimate natural wildfire emissions of black carbon (BC) and organic carbon (OC) particles, which are passed to GEOS-Chem, a 3-D chemical transport model, to simulate the transport and distribution of wildfire smoke across the western United States (WUS)
Our study focuses on carbonaceous particulate matter (PM), which are the main components in wildfire smoke (Chow et al, 2011)
Summary
Both the incidence and duration of large wildfires in the forests of the western United States have increased since the mid-1980s (Westerling et al, 2006; Abatzoglou and Williams, 2016), affecting surface levels of particulate matter (Val Martin et al, 2006, 2015), with consequences for human health (Liu et al, 2017) and visibility (Spracklen et al, 2009; Ford et al, 2018). Studies suggest that a warming climate could enhance wildfires in the WUS (Yue et al, 2013; Abatzoglou and Williams, 2016), but quantifying future wildfire activity is challenging, given the uncertainties in land cover trends and in the relationships between fire and weather. Not all of these studies that attempt to predict future fire activity have accounted for changing land cover or distinguished the effects of lightning fire ignitions from human-started fires. Our goal is to understand how trends in both land cover and meteorology may affect natural fire activity and smoke air quality over the 21st century
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