Development and Evaluation of Modeling Techniques for the Study of Interactions between Urban and Point Source Plumes and Regional Atmospheres in the Formation of Secondary Pollutants

EPA Grant Number: R827028
Title: Development and Evaluation of Modeling Techniques for the Study of Interactions between Urban and Point Source Plumes and Regional Atmospheres in the Formation of Secondary Pollutants
Investigators: Odman, Mehmet Talat , McRae, D. Scott
Institution: Georgia Institute of Technology , North Carolina State University
Current Institution: Georgia Institute of Technology
EPA Project Officer: Shapiro, Paul
Project Period: January 15, 1999 through January 14, 2002 (Extended to March 31, 2002)
Project Amount: $468,324
RFA: Air Pollution Chemistry and Physics (1998) RFA Text |  Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Engineering and Environmental Chemistry

Description:

The purpose of the study is to develop new modeling techniques and build on existing ones to improve the representation of emission sources in air quality models (AQMs). The interaction of point and urban source plumes with the surrounding atmosphere involves processes of critical importance to the formation, long-range transport and fate of secondary pollutants such as ozone. Various reactive plume models were imbedded in AQMs to better resolve point source plumes, but no real benefits were reported other than those in the immediate vicinity of the sources. It is suspected that this is due to underestimating the magnitude of numerical diffusion at grid scales where information is typically transferred from the subgrid scale plume model to the grid model. Hand-over criteria will be designed considering chemical state as well as the potential numerical diffusion of the plume. Modeling techniques will be developed that can better resolve urban plumes and provide local grid refinements for a better interface with subgrid scale models.

Approach:

Most of the models will be built upon existing pieces from the investigators? earlier research. To improve transport resolution, AQMs will be coupled with high-resolution data produced by non-hydrostatic meteorological models (MMs). To assure mass conservative coupling, wind components will be adjusted using the discrete continuity equation in the AQM. Fourier analysis will be used to quantify the numerical diffusion introduced by the advection schemes as a function of Courant number and the wavelength of the plume. Finite element and adaptive grid techniques will be used to couple subgrid scale plume models with the grid model. The finite-element refinement technique has already been implemented. The adaptive grid algorithm was recently applied to solve model advection equations. This algorithm will be used in an AQM initially in the static mode where the grid will be pre-adapted to geographic location of emission sources. It will be compared to the finite-element technique in terms of solution accuracy and computational efficiency. Then processors will be developed that can provide emissions and meteorological data on adaptive grids. Finally, the model will be operated in dynamic mode where it will automatically adapt the grid to changing solution resolution requirements with emphasis on chemical reactivity. The newly developed models will be evaluated by simulating various ozone episodes and comparing their predictions to observed levels of ozone and related pollutants.

Expected Results:

This research will improve the treatment of urban and point source plumes in emission-based models and, through simulation and diagnostic evaluation, will increase the understanding of their role in long-range transport and regional air pollution problems. It will have some immediate and direct benefits to EPA programs such as NARSTO. These are: 1) Consistent methodologies for using the output from advanced non-hydrostatic MMs in various AQMs, 2) Objective hand-over criteria for subgrid-scale reactive plume models used in AQMs, 3) Guidance on selection of grid size, span, and grid refinement methodologies. In addition, the practice of coding approaches compatible with the Models-3 framework will make the tools developed and the results readily accessible to the Models-3 community. Improvement in Risk Assessment or Risk Management: There is an increasing demand in the use of AQMs by regulatory agencies for the design of emission control strategies in relation to the ozone problem. Given the estimated cost of controls and the potential risk on human health, there is a need to identify the strategies that will meet the desired air quality goals and do so at the lowest possible cost. When developing strategies, it is desirable to be able to differentiate between the effects of different types of emissions, such as elevated point or area sources. Due to these high expectations, it is more important to improve the treatment of plumes in AQMs. The control strategy design process would directly benefit from this research.

Publications and Presentations:

Publications have been submitted on this project: View all 14 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 4 journal articles for this project

Supplemental Keywords:

tropospheric, oxidants, nitrogen oxides, mathematics, analytical, Northeast, RFA, Scientific Discipline, Air, Geographic Area, Physics, Environmental Chemistry, Chemistry, mobile sources, tropospheric ozone, Engineering, Chemistry, & Physics, East Coast, air quality standards, fate and transport, Fourier Transform Infrared measurement, urban air, subgrid scale models, air quality models, air modeling, air pollution models, point source effluents, regional atmospheres, troposphere, mathematical formulations, nitrogen removal, urban air , measurement methods , plume dispersion models

Progress and Final Reports:

  • 1999 Progress Report
  • 2000 Progress Report
  • 2001 Progress Report
  • Final