Environmental Engineering Reference
In-Depth Information
8.7 An Investigation of Aloft Model Performance
for Two Episodes During the 2000 Central California
Ozone Study
Neil J.M. Wheeler, Kenneth J. Craig, and Stephen B. Reid
Sonoma Technology, Inc., 1455 N. McDowell Blvd., Petaluma, CA 94954, USA
Abstract
The Central California Ozone Study (CCOS) was a multi-year program
of meteorological and air quality monitoring, emission inventory development,
data analysis, and air quality simulation modeling. Photochemical modeling
studies were previously carried out using both the Comprehensive Air Quality
Model with Extensions (CAMx) and the Community Multiscale Air Quality
(CMAQ) model. Performance evaluations of the photochemical modeling have
shown that the models tend to underpredict peak ozone concentrations, both at the
surface and aloft, and that model performance did not meet traditional goals for
ozone. The objective of this study was to understand and improve model perform-
ance for ozone and ozone precursors aloft. Data analysis of surface and aloft air
quality and meteorological data was used to characterize the episodes studied.
Model-to-measurement comparisons of air quality, meteorological, and integrated
(e.g., pollutant flux) values, and sensitivity analyses were used to investigate
model performance. These analyses suggested that emission estimates, particularly
for wildfires, and regional transport and recirculation of ozone aloft through
model's boundaries may account for a significant portion of the underprediction of
ozone concentrations.
Keywords
Air quality, ozone, California, model performance, CCOS, CAMx,
CMAQ
1. Introduction
The Central California Ozone Study (CCOS) was a multi-year program of
meteorological and air quality monitoring, emission inventory development, data
analysis, and air quality simulation modeling. Photochemical modeling studies have
been carried out using both the Comprehensive Air Quality Model with Extensions
(CAMx) (ENVIRON International Corporation, 2004) and the Community Multi-
scale Air Quality (CMAQ) model (National Exposure Research Laboratory, 1999).
Early performance evaluations of the photochemical modeling have shown that
