AERCOARE: An overwater meteorological preprocessor for AERMOD

Area of Science:

• Atmospheric Science
• Environmental Engineering
• Meteorological Modeling

Background:

• Offshore air quality modeling traditionally requires separate systems from onshore applications.
• The U.S. Environmental Protection Agency (EPA) Regulatory Model (AERMOD) is a standard for onshore dispersion modeling.
• Existing offshore models may not fully leverage advancements in meteorological data processing.

Purpose of the Study:

• To introduce AERCOARE, a meteorological preprocessor designed for AERMOD for offshore applications.
• To evaluate the performance of the combined AERCOARE-AERMOD modeling approach against existing methods.
• To assess the viability of a unified modeling system for both offshore and onshore regulatory dispersion modeling.

Main Methods:

• Implementation of Coupled-Ocean Atmosphere Response Experiment (COARE) algorithms within AERCOARE for predicting surface energy fluxes and stability.
• Evaluation of the AERCOARE-AERMOD model performance using tracer measurements from four overwater field studies.
• Comparison of AERCOARE-AERMOD results with the EPA's Offshore Coastal Model (OCM) and the California Puff-Advection Model (CALPUFF).

Main Results:

• The AERCOARE-AERMOD approach showed improved performance when lateral turbulence data were available and key AERMOD inputs were constrained (e.g., mixed layer height > 25m, Monin-Obukhov length > 5m).
• Model performance was comparable to the Offshore Coastal Model (OCM) for the studied tracer experiments.
• While CALPUFF showed better performance in one study, AERCOARE-AERMOD demonstrated comparable measures in others.

Conclusions:

• The combined AERCOARE-AERMOD modeling approach is a viable alternative for many offshore regulatory applications.
• This unified approach simplifies regulatory practices by allowing the use of a single dispersion model for both offshore and onshore scenarios.
• Future enhancements to AERMOD can be directly applied to offshore air quality permitting through this integrated system.