Characterizing the Climate Impacts of Brown Carbon
Brown carbon (BrC) emissions from residential, agricultural, and wildfire burning activities are a highly seasonal, episodic, and poorly characterized fraction of fine particulate matter (PM2.5) in California. In addition, secondary formation of additional carbonaceous particle mass in urban areas may contribute even more light-absorbing BrC year round. These types of BrC may have substantial impacts on climate in California and worldwide. Through a multi-institution collaboration, this study identified and characterized the contribution of BrC to climate forcing in California by (1) providing PM1 and PM2.5 physical measurements and chemical analyses of fine particles that constrain the chemical concentrations and optical properties of burning emissions, (2) quantifying the BrC organic components and the multi-wavelength absorption from burning emissions and from atmospheric formation of secondary components at two California locations, and (3) examining the globally and regionally-averaged climate response of BrC. We looked at areas with significant residential burning in the San Joaquin Valley (Fresno) and with photochemical aerosol formation in the South Coast Air Basin (Fontana) to characterize their different mixes of emission sources and seasonality.
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