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

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 (+ 1.4) ppbv in eastern China, + 1.6 (- 0.5) ppbv in the eastern U.S., and + 1.3 (+ 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 weakens surface shortwave radiative forcing of secondary organic aerosols leading to increased temperature and O₃ concentrations in the eastern U.S. This study highlights the importance of interactions between O₃ and vegetation with regard to O₃ concentrations and the resultant air quality. [ABSTRACT FROM AUTHOR]