Journal ArticleA Vertically Resolved Canopy Improves Chemical Transport Model Predictions of Ozone Deposition to North Temperate ForestsVermeuel, Michael P; Millet, Dylan B; Farmer, Delphine K; Ganzeveld, Laurens N; Visser, Auke J; Alwe, Hariprasad D; Bertram, Timothy H; Cleary, Patricia A; Desai, Ankur R; Helmig, Detlev; Kavassalis, Sarah C; Link, Michael F; Pothier, Matson A; Riches, Mj; Wang, Wei; Williams, Sara<title>Abstract</title> <p>Dry deposition is the second largest tropospheric ozone (O₃) sink and occurs through stomatal and nonstomatal pathways. Current O₃uptake predictions are limited by the simplistic big‐leaf schemes commonly used in chemical transport models (CTMs) to parameterize deposition. Such schemes fail to reproduce observed O₃fluxes over terrestrial ecosystems, highlighting the need for more realistic treatment of surface‐atmosphere exchange in CTMs. We address this need by linking a resolved canopy model (1D Multi‐Layer Canopy CHemistry and Exchange Model, MLC‐CHEM) to the GEOS‐Chem CTM and use this new framework to simulate O₃fluxes over three north temperate forests. We compare results with in situ measurements from four field studies and with standalone, observationally constrained MLC‐CHEM runs to test current knowledge of O₃deposition and its drivers. We show that GEOS‐Chem overpredicts observed O₃fluxes across all four studies by up to 2×, whereas the resolved‐canopy models capture observed diel profiles of O₃deposition and in‐canopy concentrations to within 10%. Relative humidity and solar irradiance are strong O₃flux drivers over these forests, and uncertainties in those fields provide the largest remaining source of model deposition biases. Flux partitioning analysis shows that: (a) nonstomatal loss accounts for 60% of O₃deposition on average; (b) in‐canopy chemistry makes only a small contribution to total O₃fluxes; and (c) the CTM big‐leaf treatment overestimates O₃‐driven stomatal loss and plant phytotoxicity in these temperate forests by up to 7×. Results motivate the application of fully online vertically explicit canopy schemes in CTMs for improved O₃predictions.</p>AGU2024-12-2810618739Journal of Geophysical Research: Atmospheres129242169-897Xhttps://doi.org/10.1029/2024JD0420922313772; 1822420National Science Foundation