Impacts of increasing aridity and wildfires on aerosol loading in the intermountain Western US

Abstract

Feedbacks between climate warming, land surface aridity, and wildfire-derived aerosols represent a large source of uncertainty in future climate predictions. Here, long-term observations of aerosol optical depth, surface level aerosol loading, fire-area burned, and hydrologic simulations are used to show that regional-scale increases in aridity and resulting wildfires have significantly increased summertime aerosol loading in remote high elevation regions of the Intermountain West of the United States. Surface summertime organic aerosol loading and total aerosol optical depth were both strongly correlated (p<0.05) with aridity and fire area burned at high elevation sites across major western US mountain ranges. These results demonstrate that surface-level organic aerosol loading is dominated by summertime wildfires at many high elevation sites. This analysis provides new constraints for climate projections on the influence of drought and resulting wildfires on aerosol loading. These empirical observations will help better constrain projected increases in organic aerosol loading with increased fire activity under climate change.

US particulate matter air quality improves except in wildfire-prone areas

“…S1B) indicates a low uncertainty in Krige trends in the Northwest and, therefore, a robust interpolated trend. The increase in high-quantile Northwest PM 2.5 is consistent with previous work showing an increase in organic aerosol correlated with fire area in the Rocky Mountain region (23). Our analysis implies that most areas within the Northwest, with the exception of the Seattle-Portland urban corridor, show a positive trend in the 98th quantile PM 2.5 due to wildfire influence.…”

Multidecadal trend analysis of in situ aerosol radiative properties around the world

“…The largest median slopes are found in Asia and in the Pacific (+0.13 and 0.14 % yr −1 , respectively), whereas the decreasing median slopes in other regions are relatively small (< 0.01 % yr −1 ). The beginning of the decrease in the aerosol burden varies with region; the earliest decrease is found in Europe in the 1980s (Tørseth et al, 2012), followed by North America in the 1990s (Bodhaine and Dutton, 1993;Hand et al, 2012) and by Asia some 10-15 years ago (Sogacheva et al, 2020;Zhao et al, 2019;Paulot et al, 2018). The median slope of the ω 0 trends seems to be proportional to the length of the mitigation efforts, which for some relevant pollutants (e.g., black carbon, SO 4 and NO x ) are still ongoing.…”

Wildfire‐Smoke Aerosols Lead to Increased Light Use Efficiency Among Agricultural and Restored Wetland Land Uses in California's Central Valley

“…In western North America, increased spring and summer temperatures (Keyser & Westerling, 2017;Westerling et al, 2006), earlier snowmelt (Westerling, 2016;Westerling et al, 2006), reduced fuel moisture (Abatzoglou & Williams, 2016), and overstocked forests (Agee & Skinner, 2005;Fellows & Goulden, 2008) have increased the duration and intensity of the fire season (Dennison et al, 2014;Spracklen et al, 2009;Westerling et al, 2006). Future climate simulations (Barbero et al, 2015;Flannigan et al, 2013) predict significant increases in the frequency and intensity of smoke in the western United States (Liu et al, 2016), which come with large increases in summertime carbon aerosols by midcentury (Hallar et al, 2017;Spracklen et al, 2009;Yue et al, 2013). Fire air pollution-in the form of particulate matter (PM 10 ), fine particulate matter (PM 2.5 ), and ozone (O 3 ) pollution-is harmful for human health (Anenberg et al, 2010;Lelieveld et al, 2015;Pope et al, 2009;Reid et al, 2019) and costly economically (Fann et al, 2017;Rappold et al, 2014;Rittmaster et al, 2006), but its effect on ecosystems is uncertain.…”