Environmental Engineering Reference
In-Depth Information
2.9 The WRF-CMAQ Integrated On-line Modeling
System: Development, Testing, and Initial Applications
Rohit Mathur
1
, Jonathan Pleim
1
, David Wong
1
, Tanya Otte
1
, Robert
Gilliam
1
, Shawn Roselle
1
, Jeffrey Young
1
, Francis Binkowski
2
,
and Aijun Xiu
2
1
United States Environmental Protection Agency
2
University of North Carolina, Chapel Hill, NC, USA
Abstract
Traditionally, atmospheric chemistry-transport and meteorology
models have been applied in an off-line paradigm, in which archived output on the
dynamical state of the atmosphere simulated using the meteorology model is used
to drive transport and chemistry calculations of atmospheric chemistry transport
model (CTM). A modeling framework that facilitates coupled on-line calculations
is desirable since it (1) provides consistent treatment of dynamical processes and
reduces redundant calculations, (2) provides ability to couple dynamical and
chemical calculations at finer time-steps and thus facilitates consistent use of data,
(3) reduces the disk-storage requirements typically associated with off-line appli-
cations, and (4) provides opportunities to represent and assess the potentially
important radiative effects of pollutant loading on simulated dynamical features. A
coupled on-line atmospheric modeling system is developed based on the Weather
Research and Forecasting (WRF) meteorological model and the Community
Multiscale Air Quality (CMAQ) air quality modeling system. The flexible design
of the system facilitates consistent configurations for both on-line and off-line
modeling paradigms as well as the systematic investigation of the impacts of fre-
quency of data exchange between the dynamical and chemical calculations as well
as feedback effects of chemical concentrations on meteorological process.
1. Introduction
While the role of long-lived greenhouse gases on modulating the Earth's radiative
budget has long been recognized, it is now well acknowledged that the increased
tropospheric loading of aerosols can also affect climate in multiple ways. Aerosols
can enhance reflection of solar radiation both directly, by scattering light in clear
air and indirectly by increasing the reflectivity of clouds. On the other hand, organic
aerosols and soot absorb radiation, thus warming the atmosphere. Current esti-
mates of aerosol radiative forcing are, however, quite uncertain. The major sources
