Evidence for long-range transport of carbon monoxide in the Southern Hemisphere from SCIAMACHY observations

The SCIAMACHY satellite instrument shows enhanced carbon monoxide (CO) columns in the Southern Hemisphere during the local Spring. Chemistry-transport model simulations using the new GFEDv2 biomass-burning emission database show a similar temporal and spatial CO distribution, indicating that the observed enhancements are mainly due to biomass burning (BB). Large differences between the year 2003 and 2004 are observed in both the measurements and the model for South America and Australia. This study analyzes the origin of these observed enhancements in the Southern Hemisphere. The fact that SCIAMACHY is sensitive to surface CO allows for the observation of enhanced CO columns in both emission areas and in areas that are affected by long-range transport of CO. Model results show a large contribution of South American BB CO over Australian BB regions during the 2004 BB season of up to similar to 30-35% and up to 55% further south, with smaller contributions for 2003. BB CO transported from southern Africa contributes up to similar to 40% in 2003 and similar to 30% in 2004. The results indicate that differences between SCIAMACHY CO and the model simulations over Australian BB areas are probably not only caused by uncertainties in local emissions but also in overseas emissions.