Lightning Ignited Fires over the Western United States

John Abatzoglou, University of Idaho, jabatzoglou@uidaho.edu
Bethany Bradley, University of Massachusetts, Amherst, bbradley@eco.umass.edu (Presenter)
Emily Fusco, University of Massachusetts, Amherst, efusco@cns.umass.edu
Jennifer Balch, University of Colorado-Boulder, jennifer.balch@colorado.edu

Discerning natural versus anthropogenic sources of fire is critical for both landscape coupled fire-vegetation modeling and land management operations. We asked the following questions: 1) What is the seasonal and geographic variability in the percent of fire ignitions that are lighting caused across the western US? 2) How does the percent of lightning fires from MODIS compare with fire records reported by agencies? 3) How do these vary across geographically and by ecoregions? 4) Do climate-fire relationships differ between lightning ignited and non-lightning ignited wildfires? We explored these questions using over 100,000 unique ignitions from the MODIS burned area product over 13 years covering the 11 western states. Cloud-Ground lightning strike data were obtained from the NLDN (2000-2009) and the NAPLN (2010-2012) datasets. MODIS-derived ignitions points were considered to be lightning caused if a lightning strike occurred < 3 days prior to and < 4-km from the ignition location. This may miss hold-over fires. Palmer Drought Severity Index (PDSI) and Energy Release Component (ERC) were acquired from the 4-km gridded surface meteorological dataset of Abatzoglou (2013) using voxels co-located with ignition points. (Quality controlled fire database reported by agencies from 1992-2012 from Short (2014) provide information on cause of fire.) Lightning accounts for around 35% of all ignitions across the western US, albeit with higher proportions across the interior during the summer months. MODIS derived ignitions were attributed to lightning at a significantly lower rate (18%). Strong synchronicity between annual burned area by lightning and anthropogenic causes across most ecoregions. These are reflected in drought metrics although human-caused fire in SW Mountains more strongly correlated to drought than lightning-caused fire. Large fires attributed to human and lightning cause follow slightly different trajectories of fire danger in some ecoregions.

Presentation Type:  Poster

Session:  Theme 4: Human influence on global ecosystems   (Mon 4:30 PM)

Associated Project(s): 

• Balch, Jennifer: Understanding Climate and Land Use Drivers of Invasive-Grass Fueled Fires Across the Western U.S. ...details

Poster Location ID: 26