Evaluation of low wind modeling approaches for two tall-stack databases

Abstract

AERMOD was evaluated with two tall stack databases (in North Dakota and Indiana) in areas of both flat and elevated terrain. AERMOD cases included the regulatory default mode, low wind speed beta options, and use of the Sub-Hourly AERMOD Run Procedure (SHARP). The low wind beta options show improvement in model performance (especially in higher terrain areas), helping to reduce some of the over-prediction biases currently present in regulatory default AERMOD. The SHARP results are relatively unbiased and show that this approach should be seriously considered to address situations dominated by low-wind meander conditions.

Air Toxics and Other Volatile Organic Compound Emissions from Unconventional Oil and Gas Development

“…In a dispersion model simulation, higher concentrations are typically more common at night, when dispersion can decrease with development of a stable nocturnal boundary layer that traps emitted pollutants near the ground, as observed in previous studies in the region . Because dispersion during stagnation periods is challenging to simulate accurately, future field campaigns should evaluate the actual potential for elevated acute exposures, focusing on periods when high emission activities occur in combination with shallow boundary layers and low wind speeds.…”

Dealing with the One‐Hour SO2 NAAQS Implementation

“…Evaluation tests for AERMOD, the EPA's preferred model, indicate that modeled concentration gradients of design values can be significantly overstated. 6 Further, there are limitations in AERMOD's formulation that can lead to substantial model overpredictions, especially in high terrain areas, as discussed below.…”

A Procedure to Select Meteorological Data for Air Dispersion Modeling of Pesticide Applications in California

“…Faulkner et al () demonstrated that AERMOD estimated the highest 1‐h and 24‐h average concentrations of a rural ground‐level area source at 1 m/s wind speed and the maximum concentrations decreased with increasing wind speed. In an AERMOD evaluation study using 2 tall stack databases, both air monitoring data and air dispersion modeling results suggested that high ground‐level concentrations often occurred in low wind speed (LWS) conditions (Paine et al ). The LWS conditions could cause diminished dispersion of pollutants in the air (Pasquill ).…”