Atmospheric and Surface Climate Associated With 1986–2013 Wildfires in North America

Abstract

We analyze climate simulations conducted with the RegCM3 regional climate model on 50‐ and 15‐km model grids to diagnose the dependence of wildfire incidence and area burned variations on monthly climate long‐term means and anomalies over North America for the period 1986–2013. We created a new wildfire database by merging the Fire Program Analysis Fire‐Occurrence Database, the National Interagency Fire Center Fire History Data, and the Canadian National Fire Database. The database includes 2,083,865 daily fire starts that burned a total of 1.25 × 108 ha in North America. We derive long‐term climatologies, standardized gamma indices, and composite climate anomalies of atmospheric circulation (500‐hPa height and wind) and various surface fields (e.g., solar radiation, soil moisture, vapor pressure deficit, and latent and sensible heat fluxes) to illustrate the climatology of burned area. The immediate and lagged monthly atmospheric circulation and surface climate anomalies differentiate high‐ and low‐fire years and the role of El Niño–Southern Oscillation in wildfire occurrence. Our approach demonstrates the association of the seasonal cycles of wildfire and climate and the strong role of climatic variability in modulating the seasonal cycle as a control of wildfire on monthly time scales.

The relationship between the polar jet stream and extreme wildfire events in North America

“…5) showed on average that events are associated with formation of an upper-level atmospheric ridge and corresponding positive geopotential height anomalies centered on each event. This finding is consistent with the synoptic-scale patterns that are well known to lead to above average surface temperatures (Horton et al 2016;Teng and Branstator 2017) and that are suitable for the drying of fuels and large wildfire events (Johnson and Wowchuk 1993;Skinner et al 1999Skinner et al , 2002Brewer et al 2013;Hostetler et al 2018;Wahl et al 2019). We verified that these patterns occurred concomitantly with anomalous surface temperatures and other surface weather variables with composites that showed positive anomalies in mean temperature and VPD and negative anomalies in daily precipitation (Figs.…”

“…There has therefore been an impetus to relate wildfire activity and surface fire weather with upper air and synoptic scale features (Flannigan and Wotton 2001), as evident by the large number of studies linking the two. Of particular note, studies have shown a robust correlation exists between area burned and positive 500-hPa geopotential height anomalies (Johnson and Wowchuk 1993;Nash and Johnson 1996;Gedalof et al 2005;Macias Fauria and Johnson 2006;Hostetler et al 2018;Skinner et al 1999Skinner et al , 2002. In addition, a feature of mid-tropospheric atmospheric flow commonly associated with extreme fire weather is atmospheric blocking, as evident in persistence of 500-hPa geopotential height anomalies (Johnson and Wowchuk 1993;Skinner et al 1999;Gedalof et al 2005;Hoinka et al 2009).…”

Long‐Term Trends of High Aerosol Pollution Events and Their Climatic Impacts in North America Using Multiple Satellite Retrievals and Modern‐Era Retrospective Analysis for Research and Applications version 2

“…Statistically significant positive trends in AOD from organic carbon and, to a lesser extent, AOD from black carbon extend beyond the northwestern United States and indeed are present across almost the entire domain, although the magnitude of change demonstrates a west-to-east gradient ( Figure 5). These tendencies are linked to trends in wildfire frequency (Westerling, 2016) and intensity due to both natural climate variability (Hostetler et al, 2018) and anthropogenic forcing (e.g., Abatzoglou & Williams, 2016), and the subsequent advection of the wildfire plumes from the U.S. Northwest and Southwest Canada into the eastern United States and eastern Canada (Brey et al, 2018;Hoff et al, 2005). The significant negative total AOD trends over the eastern United States are clearly dominated by declines in SO 2 emissions and the associated reduction sulfate aerosol abundance (Leibensperger et al, 2012b;Sullivan et al, 2017;Zhao et al, 2017; Figure 5).…”

Wildfire activity in northern Rocky Mountain subalpine forests still within millennial-scale range of variability

“…It is also possible that the effects of strong and persistent La Niña-like conditions in the tropical Pacific during the MCA [50,51] overrode the influence of any temperature changes in the Northern Rockies. La Niña conditions are associated with above-average winter and spring precipitation in the northwestern U.S., and warm, dry climate conditions and above-average fire activity in the southwest and the Southern Rockies [82]. Given these regional differences in the effects of ENSO variation, it is not surprising that fire activity responded differently in the two regions during the MCA.…”