Abstract
Abstract. We investigated the effects of fire-induced plume-rise on the simulation of carbon monoxide (CO) over Africa and its export during SAFARI 2000 using the NCAR Community Atmosphere Model (CAM) with a CO tracer and a plume-rise parameterization scheme. The plume-rise parameterization scheme simulates the consequences of strong buoyancy of hot gases emitted from biomass burning, including both dry and cloud-associated (pyro-cumulus) lofting. The current implementation of the plume-rise parameterization scheme into the global model provides an opportunity to examine the effect of plume-rise on long-range transport. The CAM simulation with the plume-rise parameterization scheme seems to show a substantial improvement of the agreements between the modeled and aircraft-measured vertical distribution of CO over Southern Africa biomass-burning area. The plume-rise mechanism plays a crucial role in lofting biomass-burning pollutants to the middle troposphere. In the presence of deep convection we found that the plume-rise mechanism results in a decrease of CO concentration in the upper troposphere. The plume-rise depletes the boundary layer, and thus leaves lower concentrations of CO to be lofted by the deep convection process. The effect of the plume-rise on free troposphere CO concentration is more important for the source area (short-distance transport) than for remote areas (long-distance transport). A budget analysis of CO burden over Southern Africa reveals the plume-rise process to have a similar impact as the chemical production of CO by OH and CH4. In addition, the plume-rise process has an minor impact on the regional export. These results further confirm and extend previous findings in a regional model study. Effective lofting of large concentration of CO by the plume-rise mechanism also has implications for local air quality forecasting in areas affected by other fire-related pollutants.
Highlights
Carbon Monoxide (CO) is one of the principal pollutants in the atmosphere and has an important impact on the chemical production of tropospheric ozone
The Community Atmosphere Model (CAM) simulation was evaluated using ground-based, aircraft, and MOPITT satellite measurements made during SAFARI 2000
We focus on the comparison between the model and MOPITT Level 3 (L3) CO at 700 hPa
Summary
Carbon Monoxide (CO) is one of the principal pollutants in the atmosphere and has an important impact on the chemical production of tropospheric ozone. Biomass burning releases a large amount of thermal energy that creates a strong updraft This updraft has a huge impact on tracer distributions through a direct and rapid injection into the free troposphere as well as the stratosphere (Fromm et al, 2000; Jost et al, 2004; Freitas et al, 2006; Rosenfeld et al, 2007). Various models (Liousse et al, 1996; Freitas et al, 2006; Turquety et al, 2007; Matichuk et al, 2007; Wang et al, 2006) have estimated the impact of the biomass burning on simulated CO or aerosol distributions. We illustrate the regional effects of plume-rise parameterization on the vertical distribution of CO and its export to the Atlantic Ocean and Indian Ocean by a global model.
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