A comparison of satellite observations of Fire Radiative Power with observed wildfire combustion efficiency from the Mount Bachelor Observatory

The 2012 fire season in the western U.S. was one of the largest in recent years, and predictions for the 2013 fire season also describe significant burned area across the region. We conducted intensive field campaigns at Mount Bachelor Observatory (MBO; 2.8 km a.s.l. in central Oregon) during the summers of 2012 and 2013 (July-September). A broad range of species were observed during the 2012-2013 campaigns, including CO, CO2, ozone, mercury, NOx, NOy, PAN, EC, OC, and aerosol scattering, absorption and chemical composition. We are investigating the relationship between enhancements of aerosols and chemical species, the combustion efficiency of fires, and satellite measurements of Fire Radiative Power (FRP), which we believe will be useful for improving the modeling of wildfires and their air quality impacts.

We report on 18 wildfire plumes observed at MBO during 2012, and additional plumes that will be measured during the 2013 field campaign. First, we quantify the relationship between the enhancements of aerosols and chemical species—relative to enhancements of CO and CO2—and the Modified Combustion Efficiency (MCE) of the plumes (MCE = ΔCO2/ (ΔCO+ΔCO2)). Initial results show an exponential relationship between MCE and both aerosol scattering and EC enhancements (R2 = 0.45- 0.52, p <=0.05), which holds true when correcting for plume transport time. Secondary species, such as ozone, do not have as clear of a relationship with MCE. Second, we investigate the relationship between observed MCE and FRP derived from the MODIS instruments on the Aqua and Terra satellites. FRP data is available for 6 of the 18 wildfire plumes observed in 2012, and there is a strong linear relationship between average FRP and MCE for 5 of those plumes (R2 = 0.82, p <=0.05). MODIS data shows that the sixth plume has significantly higher Aerosol Optical Depth (AOD) than the other plumes (0.70, compared to 0.05-0.40), suggesting that high AOD may limit the usefulness of this type of analysis for some fire plumes. Additional data points will be added to this analysis at the close of the 2013 fire season.