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  • Author or Editor: Francis S. Binkowski x
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Francis S. Binkowski, Saravanan Arunachalam, Zachariah Adelman, and Joseph P. Pinto

Abstract

A prototype online photolysis module has been developed for the Community Multiscale Air Quality (CMAQ) modeling system. The module calculates actinic fluxes and photolysis rates (j values) at every vertical level in each of seven wavelength intervals from 291 to 850 nm, as well as the total surface irradiance and aerosol optical depth within each interval. The module incorporates updated opacity at each time step, based on changes in local ozone, nitrogen dioxide, and particle concentrations. The module is computationally efficient and requires less than 5% more central processing unit time than using the existing CMAQ “lookup” table method for calculating j values. The main focus of the work presented here is to describe the new online module as well as to highlight the differences between the effective cross sections from the lookup-table method currently being used and the updated effective cross sections from the new online approach. Comparisons of the vertical profiles for the photolysis rates for nitrogen dioxide (NO2) and ozone (O3) from the new online module with those using the effective cross sections from a standard CMAQ simulation show increases in the rates of both NO2 and O3 photolysis.

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Robert E. Eskridge, Francis S. Binkowski, J. C. R. Hunt, Terry L. Clark, and Kenneth L. Demerjian

Abstract

A finite-difference highway model is presented which uses surface layer similarity theory and a vehicle wake theory to determine the atmospheric structure along a roadway. Surface similarity is used to determine the wind profile and eddy diffusion profiles in the ambient atmosphere. The ambient atmosphere is treated as a basic-state atmosphere on which the disturbances due to vehicle wakes are added. A conservation of species equation is then solved using an upstream-flux corrected technique which insures positive concentrations. Simulation results from the highway model are compared with 58 half-hour periods of data (meteorological and SF6 tracer) taken by General Motors. The results show that the predictions of this model are closer to the observations than those of the Gaussian-formulated EPA highway model (HIWAY).

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