Incorporation of RLINE into AERMOD: An update and evaluation for mobile source applications

Area of Science:

• Atmospheric science
• Air quality modeling
• Environmental engineering

Background:

• The RLINE model, initially for roadway applications, was integrated into AERMOD in 2019.
• Previous evaluations indicated a need to refine RLINE's dispersion parameters compared to AERMOD's AREA and VOLUME sources.

Purpose of the Study:

• To update and evaluate the RLINE source type within AERMOD.
• To address performance discrepancies identified in earlier comparisons.
• To enhance the accuracy of roadway emission dispersion modeling.

Main Methods:

• Modified RLINE vertical wind profiling and added terrain/meander weighting.
• Updated dispersion parameterization using computational optimization.
• Evaluated the updated RLINE against AREA and VOLUME sources using multiple tracer studies and transportation projects.

Main Results:

• The updated RLINE formulation demonstrated improved performance across various evaluations.
• Model intercomparisons showed closer agreement between RLINE, AREA, and VOLUME source types.
• Enhanced accuracy in predicting concentrations for highway hot-spot scenarios.

Conclusions:

• The revised RLINE source type offers improved accuracy for roadway air dispersion modeling within AERMOD.
• Practitioners can now utilize an enhanced RLINE model with greater confidence.
• The study provides essential insights into RLINE's formulation and its performance relative to other AERMOD source types.