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Reconstructing U.S. Wildland Fire Trends

The ecological, economic and health and safety concerns surrounding wildland fires are driving the need to better understand climate-fire interactions. One component of climate-fire interactions is the relationship between weather conditions concurrent with burning (i.e., fire danger) and the magnitude of fire activity. To date most relationships have been developed using monthly or seasonally averaged fire danger indexes and total accumulated burned area. This project extends and resolves these relationships by synchronizing a daily gridded fire danger climatology with daily satellite observations of fire activity collected with the Moderate Resolution Imaging Spectroradiometer (MODIS).

Results reveal that modern relationships (2003 – 2014) between fire danger and fire activity vary regionally, but in general, fires across the majority of the continental U.S. (CONUS) are more likely to be present and burning more vigorously as fire danger increases. Applying modern relationships to the entire climatology (1979 – 2014) indicates that changes in fire danger have significantly increased the number of days per year that fires are burning across 42 - 49% of CONUS (by area) whilst also significantly increasing daily fire growth and the daily heat released by fires across 37 – 45% of CONUS. Increases in the fire activity season length coupled with an intensification of daily burning characteristics resulted in a CONUS-wide +0.02 Mhayr-1 trend in burned area, a +10.6 g m-2 yr-1 trend in the amount of fuel consumed per unit burned area, and ultimately a +0.51 Tgyr-1 trend in dry matter consumption.

Overall this project has found that synchronizing spatially resolved fire danger indices with satellite observations of fire activity offers opportunities to develop modern associations between daily environmental conditions and daily burning characteristics. Moreover the application of modern associations provides a pathway for both reconstructing as well as forecasting changes in regional fire occurrence and burning characteristics solely from changes in fire danger.

Image: map comparison
Modified: Apr 20, 2017

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Freeborn, P. H., W. M. Jolly, and M. A.Cochrane (2016), Impacts of changing fire weather conditions on reconstructed trends in U.S. wildland fire activity from 1979 to 2014, J. Geophys.Res. Biogeosci., 121, doi:10.1002/2016JG003617.