Use of a Regional Climate Model to Diagnose Circulation and Surface Climate Controls of Wildfire in North America

Abstract:

We explore monthly North American climate and wildfire relationships through joint analysis of a new wildfire data base and climate simulations that we conducted with the RegCM3 regional climate model. We derived the new data base, which covers 1986-2012, by screening and merging the US FPA-FOD, US NIFC and Canadian CNFDB data guided by an analysis that included the examination of “heavy-tailed” statistical distributions (Pareto and tapered Pareto) in order to maximize the number of combined records while minimizing potential irregularities and noise such as over- and under-reporting and spurious data. We associate area burned from lightning-set wildfires, as registered to the start date of the fires, with the simulated atmospheric circulation and the surface water and energy balances at 50 km over NA and at 15 km for 4 sub-regions of NA. Our 50-km results clearly associate the seasonal cycle and spatial distribution of wildfire in the US and Canada with the seasonal cycle of atmospheric circulation and surface climate, in particular to solar and long-wave radiation and latent and sensible heating. We also use the 50‑km model output to diagnose the within-season temporal and spatial characteristics of wildfire (e.g., the Northern Rockies versus the Boreal forest) and the characteristics of individual fire years. Over the 15-km sub-regions, we use composite anomalies of the surface water and energy balances to differentiate the spatial and temporal controls of high- and low-fire years and to assess the role of interannual variability in the fire record