Black carbon: ambient intercomparisons of physical and optical properties
Authors
Allison C Aiken — Los Alamos National Laboratory
Bradley Flowers — Los Alamos National Laboratory
Kyle Gorkowski — Los Alamos National Laboratory
Manvendra K. Dubey — Los Alamos National Laboratory
Category
Aerosol Properties
Description
Currently, absorbing aerosols are thought to be the most uncertain factor in atmospheric climate models (~0.4–1.2 W/m2), and potentially the second most important factor after CO2 in global warming (1.6 W/m2; Ramanathan and Carmichael, Nature Geoscience, 2008; Myhre, Science, 2009). While most well-recognized atmospheric aerosols, e.g., sulfate from power plants, have a cooling effect on the atmosphere by scattering solar radiation, black carbon (BC or “soot”) absorbs sunlight strongly, which results in a warming of the atmosphere. Direct online measurements of BC are made with the Single Particle Soot Photometer (SP2), which detects BC by incandescence from individual particles. Measurements from the SP2 are combined with absorption measurements from the three-wavelength photoacoustic soot spectrometer (PASS-3) at 405, 532, and 781 nm and the ultraviolet photoacoustic soot spectrometer (PASS-UV) at 375 nm to determine wavelength-dependent mass absorption coefficients (MACs) and absorption angstrom exponents (AAEs), among other optical properties. Ambient measurements of different BC types were collected during three different campaigns. (1) High mass concentrations of biomass burning were sampled during the Las Conchas fire, the largest wildfire in New Mexico history that started in the Jemez Mountains in Northern New Mexico and burned over 100,000 acres during the summer of 2011. (2) Low mass concentrations of aged transported “background” pollution were sampled during BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen – Rocky Mountain Biogenic Aerosol Study), a field campaign that was located in the Manitou Forest Observatory near Colorado Springs, Colorado, in summer 2011. (3) Fresh highway, aged outflow, and wood-burning BC types were sampled during the ClearfLo (Clean Air for London) campaign in Detling, England, during winter 2012. Optical properties are compared from these different BC types and compared with laboratory measurements, and size-resolved information is used to predict the absorptive effects of these climate-relevant aerosols on our atmosphere.
