Developing a spatially and temporally resolved emission inventory for photochemical modeling in the City of Cape Town and assessing its uncertainty

In an urban environment where reactive pollutants are emitted, it is critically important that atmospheric chemistry be considered in modeling and air quality management including the evaluation of secondary pollutants such as ozone. This may be achieved through photochemical modeling, which is reliant on detailed, grid resolved emissions inventories. The US-EPAʹs approved Emissions Processing System (EPS) is used to develop a temporally and spatially resolved emissions inventory for the City of Cape Town for use in the Dynamic Air Pollution Prediction System (DAPPS). Included in this inventory are large and small point sources, mobile sources, and emissions from residential fuel burning and biogenic sources. Large point sources are usually well defined unlike the other source types that can have large uncertainties associated with them. In these circumstances, surrogate data are used to estimate emission rates. The FRamework for the Assessment of Uncertainties in Large-scale Emission INventories (FRAULEIN) approach to assessing uncertainty in the emissions inventory is adapted for DAPPS. A reasonable level of confidence exists for the characterization of large point sources but the two biggest source contributors namely vehicle and biogenic emissions, needs improvement.