Validation of the WRF-CMAQ Two-way Model with High Resolution MODIS Data in the CA 2008 Wildfire Case

Friday, 19 December 2014
David C. Wong1, Chenxia Cai2, Jonathan E. Pleim1, Rohit Mathur1 and Mark S. Murphy3, (1)U.S. Environmental Protection Agency, Durham, NC, United States, (2)California Air Resources Board, Sacramento, CA, United States, (3)EPA, RTP, NC, United States
Traditionally, the air quality model, CMAQ (Community Multiscale Air
Quality), is driven by the meteorology model, WRF, forming a one way
data interaction pathway without aerosol feedback. We coupled the WRF
and CMAQ models to create a two-way coupled modeling system to
facilitate feedbacks between chemistry and meteorology through the use
of memory resident buffer data files. Simulated aerosol composition and
size distributions are used to estimate the optical properties of
aerosols which are then used in the radiation calculations in WRF.
Thus, direct radiative effects of scattering and absorbing aerosols in
the troposphere estimated from the spatially and temporally varying
simulated aerosol distributions, can be fed-back to the WRF radiation
calculations, resulting in “two-way” coupling between the atmospheric
dynamical and chemical modeling components.

To examine the effectiveness of the coupled system to capture aerosol
radiative feedback effects, we conducted a simulation with 12 and 4km
resolution (10 Jun – 30 Jun 2008 and the first ten day is the spinoff
period) of a wildfire event in California. Widespread wildfires
resulted in significant particulate matter (PM) pollution during
mid-late Jun 2008 in California and surrounding states. We compare our
model with a high resolution (500m) MODIS data with model AOD result to
validate the performance of the two-way coupled model on aerosol direct
effects. We also evaluate the performance of the two-way model with and
without feedback turn on with respect to 2-m temperature and radiation