AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Chemical and Physical Properties of Smoke Plumes in the Western and Southeastern US Using Hazard Mapping System (HMS) and AERONET/IMPROVE Data
QIJING BIAN, Bonne Ford, Jeffrey R. Pierce, Sonia Kreidenweis, Colorado State University
Abstract Number: 64 Working Group: Biomass Combustion: Emissions, Chemistry, Air Quality, Climate, and Human Health
Abstract Biomass burning is a major source of summertime PM2.5 in the US. Emissions degrade air quality and are associated with negative effects on human health. According to data compiled in the National Emissions Inventory, wildfires dominate biomass burning emissions in the west while prescribed fires dominate emissions in the southeast. The different fire sizes, fuel types, and emission factors from wildfires and prescribed fires may produce emitted smoke particles with different properties, e.g. particle size, chemical composition and optical properties. We used data from the Hazard Mapping System (HMS) to track smoke plumes for 10 years from 2008 to 2017. Combining these geospatial data with AERONET data, we define “smoke days” at a particular site as those days when the smoke polygon from HMS included the coordinates of that site and only compile data for April through September, for both smoke days and non-smoke days. For the IMPROVE network, we further apply a threshold of PM2.5 larger than mean + standard deviation in the target year, so we can filter out the cases where the smoke is not at the surface. We derive the composition of smoke PM2.5 using the difference between smoky and non-smoky days. We find that elemental carbon (EC) fraction of smoke in the southeast is about half of the EC fraction in the west, consistent with more smoldering prescribed fires in the southeast. For AERONET data, inverted size distributions show that western smoke had smaller-diameter fine particles than southeastern smoke, but more coarse particles, perhaps associated with lofting of dust by western wildfires. We found that the single scattering albedo (SSA) of smoke varied from 0.937-0.946 in the west to 0.962 in the southeast, consistent with the differences in EC fraction and fire types. Higher relative humidity in the southeast may also contribute to the higher smoke SSA relative to the west. Hence, differences in fire types and conditions between the west and southeast may contribute to differences in smoke composition and optical properties.