Radiative Effects Due to Tropospheric Ozone and Carbonaceous Aerosol Enhancements Caused by Asian Wildfires During Spring, 2008

Long-range transport of ozone precursor species and carbonaceous aerosols
emitted by wildfires may affect the atmospheric composition and regional climate
far away from the location of the fires. Major outbreaks of fires occurred in 3
areas of Asia, Kazakhstan, Siberia, and Thailand, during the spring of 2008.
Satellite and aircraft-based observations and trajectory studies have identified
the transit of the plumes from these fires across the Pacific. We have conducted
simulations of the effects of these fires on the atmospheric composition using the
Real-time Air Quality Modeling System (RAQMS). RAQMS is a global scale
meteorological and chemical modeling system with unified
(stratosphere/troposphere) chemistry module. Model results, for example,
indicate that increases of 10 ppbv in upper tropospheric ozone at 180W longitude
and northern mid-latitudes in April, 2008 could be attributed to these fires. Large
increases in aerosol optical depth due to carbonaceous aerosols are also seen
nearer the fire location. Both tropospheric ozone and carbonaceous aerosols
influence the atmospheric energy balance and climate. We use an off-line
radiative transfer model along with the RAQMS chemical and aerosol analyses to
calculate the direct radiative forcing during April, 2008, due to Asian wildfire
emissions. Arctic indirect radiative forcing due to these emissions are evaluated
using RAQMS aerosol extinction analyses in conjunction with MODIS retrievals
of cloud liquid water and effective radius. We will discuss the radiative forcing
results and the relative influences of the different fire events.