Aerosol Emissions from Wildfires Constrained by Satellite Measurements and the GoCART Aerosol Model

Emissions of smoke particles from biomass burning (BB) impact air quality, visibility, human health and make important contributions to aerosol climate forcing. These aerosol effects can be dramatic in BB regions and can affect conditions far downwind from the sources due to particle transport. While chemistry transport models are the major tools in studying aerosol environmental impacts, simulations of BB emissions in these models strongly depend on the inventories that provide emission source locations and strengths. However, due to the complex nature of fires and different ways of making estimates, emission amounts differ significantly between these inventories as is shown in Figure 1.

Ratio of average GOCART-simulated  to MODIS-measured AOD for each studied fire case. Boxes colored in green show the  cases where the modeled and observed AOD agree well. Blue boxes are where the model underestimates MODIS AOD, and red – where the model overestimates. The maps are labelled by the BB emission option (described in detail in the referenced paper).

One way to constrain emission estimates in the model is to use aerosol observations. We performed a detailed study with13 global biomass burning emission estimates, including the widely used Global Fire Emission Database (GFED), Quick Fire Emission Dataset QFED used in the NASA's comprehensive global model GEOS-5, and 11 combinations of satellite products providing burned area and biomass properties usually used to estimate BB emissions.

We then used each of these 13 emission estimates as inputs to the global aerosol model GOCART. We compared the simulated aerosol optical depth (AOD), which is a quantity directly related to amount of particles in the atmosphere, to AOD measured from the satellite for 124 fire cases around the globe. Figure 2 highlights regional performance of each emission option, green color in the graphs showing the best comparison between the model and the observation, and blue and red colors showing the cases where the model's AOD is lower or higher than satellite AOD.. This result is extremely important for aerosol modelers who use these inventories, and for inventory developers, who aim to improve their products.

References:

  1. Petrenko, M. M., R. Kahn, M. Chin, A. Soja, T. Kucsera, and Harshvardhan (2012). The use of satellite measured aerosol optical depth to constrain biomass burning emissions source strength in the GOCART model. J. Geophys. Res.,  in review.

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