Many east and west coast U.S. urban areas, classified as non-attainment for ambient air pollutants, are home to major Department of Defense (DoD) facilities. DoD operations can be significant sources of air pollutants and their precursors; however, considerable uncertainty exists associated with coastal emission inventories because of the complex meteorology related to the land/sea interface. More effective predictive tools are needed to address emission inventories and to develop strategies to reduce air pollution in coastal urban areas.

The objective of this project was to develop and validate a prognostic modeling system capable of assessing the impact of coastal DoD operations on air quality.

Currently, three approaches—Eulerian, Lagrangian, and hybrid—are used to model transport, dispersion, and transformation of pollutants. The Eulerian method is used to represent the primary processes affecting chemical transformations. The Lagrangian approach avoids the computational complexities associated with the simulation of the chemical reactions, which leads to improved performance in assessing transport and dispersion. The hybrid approach combines the strengths of both the Eulerian and Lagrangian methods and may provide a unique approach for the next generation of chemical transport simulations. The components of the hybrid model developed in this project include the following: Mesoscale Meteorological Module 5 for the meteorological fields, a Lagrangian particle model for advection and dispersion, and an Eulerian chemical model within the Linkage module for the transformations. The Linkage module couples the Lagrangian and Eulerian parts of the model.

Researchers developed a hybrid modeling system that incorporates the strengths of both the Lagrangian transport/diffusion model and Eulerian multi-box chemical model. This system can readily employ alternative chemical and transport-dispersion modules and is capable of evaluating the impact of emissions from individual moving sources in space and time. As part of model testing and validation, researchers prepared an emissions inventory for the San Diego area, evaluated model performance using tracer study data, and performed an aircraft measurement program to obtain data for model validation. Researchers also used the model to assess the impact of local and transported pollutants on air quality in the San Diego area and two scenarios of interest to DoD— the impact of DoD emissions on air quality and the spatial and temporal impact of emissions from a single ship.

The results of this study will enable DoD to (1) predict the impact and influence of coastal DoD facilities on urban and regional air quality; (2) assess the contribution from individual sources to primary pollutant (directly emitted from sources) and secondary pollutant (formed by chemical reactions in the atmosphere) levels; (3) estimate the impact of new technologies, fuels, and activity patterns on air quality; and (4) design effective abatement strategies. (Project Completed - 2006)