DOE OSTI2017
Black carbon (BC) absorbs incident solar radiation, perturbs temperature gradients in the atmosphere, and indirectly impacts cloud formation and optical properties (Koch and Del Genio 2010). Deposition of BC to snow and ice surfaces alters albedo and enhances snow melt (Hansen and Nazarenko 2004; Flanner et al., 2007). The impact of BC on regional and global climates through these processes depends on its atmospheric concentration, and thus on the relative rates of emission and loss. Combustion of fossil fuels and biofuel, biomass burning, and wildfires are major sources of BC (Bond et al., 2004). Significant sinks include wet and dry deposition. Wet deposition occurs through scavenging by cloud droplets, ice crystals, and precipitation, while dry deposition refers to the direct removal of particles in the atmosphere to planetary surfaces (e.g., plant, soil, ocean, ice surfaces). Bond et al. (2013) and references therein have focused on the source, aging, and optical properties of BC, while deposition components of the BC lifecycle remain poorly constrained. This is predominantly due to the lack of observations of both total aerosol and BC deposition. Removal rates of refractory and non-refractory sub-micron aerosol by wet and dry deposition are one of the most uncertain aspects of modelling cloud condensation nuclei (CCN; Lee et al., [2013]). BC is an ideal tracer for particle deposition because it is non-volatile and effectively chemically inert, though it can become mixed with other species in the atmosphere. Unlike other aerosol species, BC remains ‘intact’ in water and has no confounding gas-phase contribution to precipitation measurements, and can thus be used to examine the relative importance of wet and dry deposition. Thus, measurements of BC deposition are not only essential for constraining BC sinks and atmospheric lifetime, but also useful for investigating aerosol deposition more broadly.
Southern Great Plains, black carbon, aerosols, sin↗