Impacts of 2006 Indonesian fires on tropical upper tropospheric carbon monoxide and ozone
1Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
3National Institute of Aerospace, Hampton, VA, USA
Abstract. We investigate the relative impacts of biomass burning emissions and dynamics on tropical upper tropospheric carbon monoxide (CO) and ozone (O3) over western and central Indonesia during the August-November 2006 fires in equatorial Asia by using a global three-dimensional model of tropospheric chemistry (GEOS-Chem) and by comparing model results with Microwave Limb Sounder (MLS) observations of upper tropospheric CO and O3. GEOS-Chem CO and O3 reproduce MLS observed enhancements from convective lifting of fire emissions. In the tropical upper troposphere (UT), fire effluents from equatorial Asia are primarily transported southwestward to the eastern tropical Indian Ocean, driven by the high-pressure systems along 10° N–15° N and 10° S–15° S latitudes, and northeastward to southeast Asia and beyond, driven by the western North Pacific subtropical high. A characteristic feature of these CO enhancements is that they lag behind biomass burning emissions (by 2–3 weeks) at the three pressure levels from 215 hPa to 100 hPa, resulting form the decreasing influence of deep convective lifting with altitude in the UT. We estimate the fire influences by contrasting one model simulation with year-specific and another with climatological biomass burning emissions. Biomass burning accounts for about 50–150 ppbv of CO and 5–20 ppbv of O3 in the tropical UT below 100 hPa during October and November, with temporal variations driven by biomass burning and deep convection. We estimate the dynamic impacts by examining the difference between a model simulation for 2006 (El Niño) and another for 2005 (neutral). The dynamic impacts are far more complex and account for up to 100 ppb of CO and 30 ppb of O3 in the tropical UT below 100 hPa. The temporal variation of the dynamic impact on CO is driven by deep convection. The variation of the dynamic impact on O3 not only depends on deep convection but also reflects the non-linearity of O3 chemistry.