Seasonal reversal of the influence of El Niño–Southern Oscillation on very large wildfire occurrence in the interior northwestern United States

Abstract

Satellite‐mapped fire perimeters and the multivariate El Niño–Southern Oscillation index were used to examine the impact of concurrent El Niño–Southern Oscillation (ENSO) phase on very large fire (VLF) occurrences over the intermountain northwestern United States (U.S.) from 1984 to 2012. While the warm phase of ENSO promotes drier and warmer than normal conditions across the region during winter and spring that favor widespread fire activity the following summer, a reduction in VLFs was found during the warm phase of ENSO during summer concurrent with the fire season. This paradox is primarily tied to an anomalous upper level trough over the western U.S. and positive anomalies in integrated water vapor that extend over the northwestern U.S. during summers when the warm phase of ENSO is present. Collectively, these features result in widespread increases in precipitation amount during the summer and a curtailment of periods of critically low‐fuel moistures that can carry wildfire.

Spatio-Temporal Linkages between Declining Arctic Sea-Ice Extent and Increasing Wildfire Activity in the Western United States

“…Further, the influence of the Atlantic Multidecadal Oscillation (AMO) has been shown to modulate the strength and spatial patterning of ENSO and PDO effects on wildfire in western North America [57]. While many of the above-described atmospheric modes of variation also have been linked to increasing wildfire activity in the western United States [21,54,[57][58][59][60], caution must be taken when establishing direct causal linkages between declining ASIE and increasing wildfire activity through correlative analyses. In short, low (high) levels of ASIE perturb atmospheric flow through interactions with latitudinal temperature gradients, which in turn can impact atmospheric thickness, zonal (meridional) flow patterns [12,16] and surface climatic conditions associated with both wildfire and specific modes of variation [21].…”

A review of the relationships between drought and forest fire in the United States

“…Regional-to-local variation in forest management (e.g., Keeley & Syphard, 2015), surface and canopy fuels, and ignitions affect how much anomalous fuel moisture conditions contribute to area burned anomalies in forest and woodland environments and ultimately determine the trajectory of fire regimes. Although ocean-atmosphere circulation anomalies affect the likelihood of drought conditions that in turn affect the probability of wildfire occurrence and spread (Swetnam & Betancourt, 1998;Collins et al, 2006;Kitzberger et al, 2007), the effect of teleconnections on seasonal climate and therefore wildfire may be transient at longer time scales (Barbero et al, 2015). For example, relationships between climate and wildfire have changed in the U.S. Pacific Northwest (Higuera et al, 2015) over a century of climate and fire observations.…”

Effects of climate oscillations on wildland fire potential in the continental United States

“…These forecasts depend heavily, however, on predictions of internal climate oscillations, including the modulated annual cycle (MAC) [Wu et al, 2008], which describes the interannual variability in the seasonal cycle, and the El Niño-Southern Oscillation (ENSO) [Ropelewski and Halpert, 1986;Ropelewski and Halpert, 1987]. These and other oscillations influence the climate in a variety of ways, resulting in subsequent impacts on wildland fire risk and potential [Gershunov and Barnett, 1998;Barbero et al, 2015;Morgan et al, 2008]. These and other oscillations influence the climate in a variety of ways, resulting in subsequent impacts on wildland fire risk and potential [Gershunov and Barnett, 1998;Barbero et al, 2015;Morgan et al, 2008].…”