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“RLINE: A Line Source Dispersion Model for Near-Surface Releases”
Citation:
Arunachalam, S., M. Snyder, A. Venkatram, D. Heist, S. Perry, AND V. Isakov. “RLINE: A Line Source Dispersion Model for Near-Surface Releases”. Presented at Annual CMAS Conference, Chapel Hill, NC, October 28 - 30, 2013.
Impact/Purpose:
The National Exposure Research Laboratory (NERL) Atmospheric Modeling and Analysis Division (AMAD) conducts research in support of EPA mission to protect human health and the environment. AMAD research program is engaged in developing and evaluating predictive atmospheric models on all spatial and temporal scales for forecasting the air quality and for assessing changes in air quality and air pollutant exposures, as affected by changes in ecosystem management and regulatory decisions. AMAD is responsible for providing a sound scientific and technical basis for regulatory policies based on air quality models to improve ambient air quality. The models developed by AMAD are being used by EPA, NOAA, and the air pollution community in understanding and forecasting not only the magnitude of the air pollution problem, but also in developing emission control policies and regulations for air quality improvements.
Description:
Growing concern about human exposure and related adverse health effects near roadways initiated an effort by the U. S. Environmental Protection Agency to reexamine the dispersion of mobile source related pollutants. These adverse effects, in combination with the fact that a significant portion of the population spending time at home, work or school within a few hundred meters of major roadways, support a need for dispersion modeling to capture the temporal and spatial variability of mobile source pollutants in the near-road environment. The RLINE (Research LINE source) model is a research grade dispersion model that is currently under development by EPA ORD for near-roadway assessments. RLINE is a part of EPA ORD’s ongoing evaluation of air quality impacts in the near-road environment. The research model is based upon a steady-state Gaussian formulation and is designed to simulate line type source emissions (e.g. mobile sources along roadways) by numerically integrating point source emissions. The current version of RLINE - RLINE 1.0 Beta - is currently formulated for near-surface releases, contains new (field study and wind tunnel based) formulations for the vertical and lateral dispersion rates, simulates low wind meander conditions, includes Monin-Obukhov similarity profiling of winds near the surface and selects plume-weighted winds for transport and dispersion calculations. The current beta version of the model is designed for flat roadways (no surrounding complexities) with future research efforts expected to accommodate new algorithms for simulating the near-source effects of complex roadway configurations (noise and vegetative barriers, depressed roadways, etc.).