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APPLICATION OF FINE SCALE AIR TOXICS MODELING WITH CMAQ TO HAPEM5
Citation:
Ching, J.K S., T E. Pierce Jr., T. Palma, W T. Hutzell, R. Tang, A. Cimorelli, AND J A. Herwehe. APPLICATION OF FINE SCALE AIR TOXICS MODELING WITH CMAQ TO HAPEM5. Presented at 2004 Models-3 Conference, Chapel Hill, NC, October 18 - 20, 2004.
Impact/Purpose:
The objective of this task is to develop and evaluate numerical and physical modeling tools for simulating ground-level concentrations of airborne substances in urban settings at spatial scales ranging from ~1-10 km. These tools will support client needs in the areas of air toxics and homeland security. The air toxics tools will benefit the National Air Toxics Assessment (NATA) program and human exposure modeling needs within EPA. The homeland security-related portion of this task will help in developing tools to assess the threat posed by the release of airborne agents. Both sets of tools will consider the effects induced by urban morphology on fine-scale concentration distributions.
Description:
This paper provides a preliminary demonstration of the EPA neighborhood scale modeling paradigm for air toxics by linking concentration from the Community Multiscale Air Quality (CMAQ) modeling system to the fifth version of the Hazardous Pollutant Exposure Model (HAPEM5). For this demonstration, annual simulations of CMAQ are performed at multiple scales at 36, 12, and 4 km grid sizes. The domain for 36 km size included the continental U. S., while the smaller grid sizes included nested domains that comprised Philadelphia and the state of Delaware. In this application, specific air toxics species were defined and added to the Carbon Bond-IV mechanism. HAPEM5 allowed for the introduction of temporal and spatial (sub-grid) variability. Temporal variability was estimated using hourly outputs for a year at each grid cell. The sub-grid variability was estimated using customized software designed to provide gridded Probability Density Functions (PDFs) to describe the concentration distributions from running the Gaussian dispersion model ISC in fine receptor mode. This application demonstrates that a more robust set of information can be generated for HAPEM5 than by applying to ISC approach. For example, this methodology provides considerably larger dynamic range of temporal and spatial variability not available using ISC alone. Moreover, using CMAQ allows for more accurate estimation of secondary species such as formaldehyde and acetaldehyde, which are not treated explicitly in models such as ISC.
The research presented here was performed under the memorandum of understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce's National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW13921548. Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies of views.