Aerosol transport and optical properties of the 2012 North American wildfires

Abstract

At the advent of the 2012 summer season, high pressure strengthened over the midsection of the United States and reached into southeastern Canada during the week of 24-29 June.  A multi-platform approach consisting of AERONET ground-based observation stations, CALIPSO satellite observations, and FLEXPART/HYSPLIT model output data is used to identify the origins of the aerosol plumes that affected much of North America in addition to the varying in-plume physico-chemical properties.  Several aerosol plumes as well as distinct aerosol haze layers were generated from ongoing wildfires and were observed by satellite and ground based observation stations in close proximity to the ridge.  The plume trajectories illustrated by the model output show the spatial extent and temporal movement of the aerosol plumes from wildfires in the intermountain region (Utah, Colorado, Wyoming, and Montana) to the eastern parts of the United States and Canada, in particular, Boulder, CO, Grand Forks, ND, Pickle Lake, ON, and the Egbert/Toronto, ON vicinity.  The extinction aerosol optical depth (t) shows the aerosol plume at each location over a period of five to six days.  The strong wavelength dependence of t (440-870 nm) at each location suggests a fine mode particle influence.  The absorption aerosol optical depth (t_abs) and single scattering albedo (w_o) indicate the aerosol plume having strong biomass particle dominance with some pollution particle influences (e.g. the Egbert and Toronto locations) due to varying amounts of strongly absorbing black carbon (BC), weakly absorbing organic carbon (OC), and apparent light absorbing organic carbon (ALAOC).  The w_o parameter suggests multiple plume origins in addition to w_o440nm > 0.95 denoting aged biomass aerosols (> 3 days old) while w_o440nm < 0.95 denotes fresh biomass aerosols (from several hours up to 3 days old).