Modeling Regional &
Global Atmospheric Chemistry Mechanisms: Observing Adverse Respiratory
Health Effects due to Tropospheric Ozone Air Pollution from Modeling
Output
Emily Saunders
SSAI
5 Feb, 10 a.m., in 2890
Abstract:
Regional air quality forecasts may be improved through the use of
global model simulations to provide boundary conditions (BCs) to
regional air quality models. The most important advantage of using
global model BCs is that these BCs can bring time-varied external
signals to the regional domain, and reflect certain event information,
such as biomass burning, stratospheric intrusion, and Asian air mass
inflow. These observations suggest that the use of global model BCs can
improve regional air quality predictions. It also points out that
further improvement in regional model predictions will require efforts
to reduce the uncertainty in the global model BCs. Additional
uncertainties are introduced in this importing process because of the
uncertainties in the global models, and because of differences in
resolution between the global and regional models, and differences in
model formations, such as chemical mechanisms.
The main goal of this research project was to create a new gas-phase
chemical mechanism for global atmospheric chemistry models, the Global
Atmospheric Chemistry Mechanism (GACM) that is based on the Regional
Atmospheric Chemistry mechanism, version 2 (RACM2). Improved global
atmospheric chemistry models with GACM can be used to supply better
initial and BCs to regional air quality models especially those that
use RACM2 because GACM and RACM2 are designed to be highly compatible
representations of atmospheric chemistry.
GACM includes marine chemistry reactions to simulate marine
environments better while maintaining a compact size. For GACM some
volatile organic compound (VOC) chemistry was simplified to make room
the additional marine chemistry and to maintain computational
efficiency. RACM2 and GACM were compared and evaluated through simple
box modes and the Weather Research & Forecasting Model coupled with
chemistry (WRF-Chem). WRF-Chem allowed RACM2 and GACM tropospheric
ozone simulations to be compared under more realistic world conditions.
California’s South Coast Air Basin (i.e. the SoCAB region) was used as
a testbed for the WRF-Chem simulations. All of these simulations showed
the compatibility of RACM2 and GACM and that these two mechanisms will
work well in a global-regional modeling system where GACM provides
boundary conditions to a regional scale model.
As a further test of the compatibility of RACM2 and GACM the WRF-Chem
simulations were processed with the EPA’s Environmental Benefits
Mapping & Analysis Program – Community Edition (BenMAP-CE) to
estimate the respiratory related human health impacts and costs within
the SoCAB region. The WRF-Chem simulations with GACM and RACM2 gave
very similar estimates of the negative respiratory health impacts and
the cost of those health impacts. Further, our work shows that
BenMAP-CE could be used to forecast routinely daily changes in air
quality health impacts and costs.
In closing, GACM will be applicable to current global models and can be
used in conjunction with RACM2 based or other regional modeling systems
to more accurately predict the amount of ozone formed in highly
polluted urban local communities especially on the west coast of the
United States.