Environmental Engineering Reference
In-Depth Information
2.20 Background Ozone in Regional-Scale Modelling
over North America
A. Chtcherbakov
1
, R. Bloxam
1
, N. Reid
2
, and Y. Hall
1
1
Ontario Ministry of the Environment, Toronto, Canada
2
Smeraldo Environmental, Toronto, Canada
Abstract
This study estimates background ozone concentrations over Eastern
North America for the year 2005 based on analysis of CMAQ (the Community
Multiscale Air Quality model) simulations with all anthropogenic emissions set to
zero.
Influences of inflow boundary conditions, land use characteristics, meteorological
conditions, and dry deposition on the background ozone concentrations were
analyzed. The spatial distributions and temporal peculiarities of ozone background
concentrations were examined with statistical analysis applied and results presented.
Keywords
Ozone, background concentrations, CMAQ simulations
Background ozone may form a significant part of the daily 8 h maximum ozone
concentrations. This can be extremely important, since the background concentration
is the level below which concentrations can not be reduced by local/regional efforts
alone.
It is essential how the background ozone concentration is defined. In this study
we consider background ozone as concentration of ozone advected into the modelling
domain as a result of anthropogenic and biogenic emissions anywhere outside the
domain (including stratospheric ozone intrusions) plus ozone generated from emis-
sions from natural, biogenic sources only, excluding anthropogenic sources inside
the domain.
To estimate the impacts of background ozone, CMAQ v4.6 (the Community
Multiscale Air Quality Model) was run for the May-September 2005 period with
all anthropogenic emissions set to zero over the domain which covers Eastern
North America
(Fig. 1)
Meteorological data to run CMAQ was obtained from
WRF v 2.2 (Weather Research and Forecast model) runs.
In this run the southern and western boundaries of the domain (usually inflow)
have ozone concentrations of 35 ppb near the surface increasing to 40, 45, 50, 60
and 70 ppb in five layers to the model top (100 mbars). The eastern and northern
boundaries (frequently outflow) have 30 ppb in the lowest layer. These values are
based on average observed ozone profiles.
