Impacts of ozone-vegetation feedbacks on surface ozone in a coupled climate-chemistry-ecosystem model

Abstract. Surface ozone (O₃) is strongly influenced by interactions between atmospheric chemistry and terrestrial ecosystems, yet these feedbacks remain insufficiently represented in Earth system models. Here, we develop a fully coupled O₃-vegetation interaction framework by integrating the terrestrial ecosystem model iMAPLE into the ECHAM-HAMMOZ Earth system model. The coupled model explicitly represents three major land-atmosphere interaction pathways, including dynamic biogenic volatile organic compound (BVOC) emissions, vegetation-mediated O₃ dry deposition, and O₃-induced vegetation damage. These feedback pathways exert heterogeneous impacts on surface O₃ concentrations due to spatial variations in vegetation characteristics and nonlinear chemical sensitivities. Changes in monoterpene emissions cause the largest global effect with widespread reductions in surface O₃, whereas isoprene-driven responses vary among regions with different chemical sensitivities. In regions with high anthropogenic emissions, such as East Asia, vegetation-mediated changes in BVOCs and dry deposition substantially amplify O₃ responses. The O₃-induced vegetation damage further modifies atmospheric chemistry by reducing BVOC emissions through leaf area loss while increasing surface O₃ by inhibiting stomatal conductance. Incorporating these processes decreases simulated global surface O₃ concentrations and alleviates the positive bias in the original model, particularly over China (relative mean bias decreases from 31.5 % to 29.7 %) and the U.S. (from 19.0 % to 7.8 %). These results demonstrate that interactive O₃-vegetation feedbacks are essential for improving the representation of atmospheric composition and ecosystem–atmosphere interactions in Earth system models.