Ozone–vegetation feedback through dry deposition and isoprene emissions in a global chemistry–carbon–climate model

Abstract

Abstract. Ozone–vegetation feedback is essential to tropospheric ozone (O3) concentrations. The O3 stomatal uptake damages leaf photosynthesis and stomatal conductance and, in turn, influences O3 dry deposition. Further, O3 directly influences isoprene emissions, an important precursor of O3. The effects of O3 on vegetation further alter local meteorological fields and indirectly influence O3 concentrations. In this study, we apply a fully coupled chemistry–carbon–climate global model (ModelE2-YIBs) to evaluate changes in O3 concentrations caused by O3–vegetation interactions. Different parameterizations and sensitivities of the effect of O3 damage on photosynthesis, stomatal conductance, and isoprene emissions (IPE) are implemented in the model. The results show that O3-induced inhibition of stomatal conductance increases surface O3 on average by +2.1 ppbv (+1.2 ppbv) in eastern China, +1.8 ppbv (−0.3 ppbv) in the eastern US, and +1.3 ppbv (+1.0 ppbv) in western Europe at high (low) damage sensitivity. Such positive feedback is dominated by reduced O3 dry deposition in addition to the increased temperature and decreased relative humidity from weakened transpiration. Including the effect of O3 damage on IPE slightly reduces surface O3 concentrations by influencing precursors. However, the reduced IPE weaken surface shortwave radiative forcing of secondary organic aerosols, leading to increased temperature and O3 concentrations in the eastern US. This study highlights the importance of interactions between O3 and vegetation with regard to O3 concentrations and the resultant air quality.