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Black carbon (BC) is emitted from combustion processes as fine particles. BC has a major role in the climate system due to its ability to absorb solar radiation and potential interactions with clouds. Comparing BC content of different smoke-impacted air masses may be uncertain if different measurement techniques (e.g., in situ, filter-based, etc.) are used to quantify BC, or if non-BC fractions influence a given measurement. The BC measurements are further complicated if the BC mass is converted from aerosol light absorption using a mass-absorption cross-section (MAC). Values of MAC are dependent on the aerosol physicochemical properties and mixing states. To investigate these potential issues, we conducted a set of combustion experiments with a wide variety of biomass fuels and combustion conditions using several concurrent BC instruments during the 2016 Fire Influence on Regional to Global Environments Experiment (FIREX) campaign.Three main research contributions have been made by this dissertation to address BC-related uncertainties. As the first contribution, we inter-compared different BC measurement techniques for the biomass burning emissions. The observed differences were then examined for correlations with aerosol chemical and optical properties. Thus as a second objective, to constrain equivalent BC estimates between different instruments, we developed a correction algorithm for filter-based absorption photometers. The third contribution of this dissertation includes the characterization of aerosol MAC utilizing data analytical approaches, in which the corrected filter-based data was among the input variables. In summary, the research conducted in this dissertation constrains uncertainties associated with BC, propagated to account for both instrument differences and natural variabilities. In particular, the models presented in this dissertation can be applied to both historic and future BC datasets to minimize measurement and observational artifacts. Reducing such artifacts will in turn reduce uncertainties associated with the predicted warming effects of BC by atmospheric chemical transport and climate models. |
