Indirect contributions of global fires to surface ozone through ozone-vegetation feedback.

Fire is an important source of surface ozone (O₃), which causes damage to vegetation and reduces stomatal conductance. Such processes can feed back to inhibit dry deposition and indirectly enhance surface O₃. Here, we apply a fully coupled chemistry-vegetation model to estimate the indirect contributions of global fires to surface O₃ through O₃-vegetation feedback during 2005-2012. Fire emissions directly increase the global mean annual O₃ by 1.2 ppbv (5.0%) with a maximum of 5.9 ppbv (24.4%) averaged over central Africa by emitting substantial number of precursors. Considering O₃-vegetation feedback, fires additionally increase surface O₃ by 0.5 ppbv averaged over the Amazon in October, 0.3 ppbv averaged over southern Asia in April, and 0.2 ppbv averaged over central Africa in April. During extreme O₃-vegetation interactions, such feedback can rise to >0.6 ppbv in these fire-prone areas. Moreover, large ratios of indirect-to-direct fire O₃ are found in eastern China (3.7%) and the eastern U.S. (2.0%), where the high ambient O₃ causes strong O₃-vegetation interactions. With likelihood of increasing fire risks in a warming climate, fires may promote surface O₃ through both direct emissions and indirect chemistry-vegetation feedbacks. Such indirect enhancement will cause additional threats to public health and ecosystem productivity. [ABSTRACT FROM AUTHOR]