surface ozone at high-Arctic sites

Dry deposition is an important removal mechanism for tropospheric ozone (O3). Currently, O3 deposition to oceans in atmospheric chemistry and transport models (ACTMs) is generally represented using constant surface uptake resistances. This is despite the fact that considering the ::::: occurs :::::: despite ::: the : role of solubility, waterside turbulence and O3 reacting with ocean water reactants such as iodide results in substantial spatiotemporal variability in O3 deposition and concentrations in marine boundary layers. We hypothesize that O3 deposition to the Arctic ocean, having a relatively low reactivity, is overestimated 5 in current models with consequences for tropospheric concentrations, lifetime and long-range transport of O3. In this study, we ::: We investigate the impact of the representation of oceanic O3 deposition to the simulated magnitude and spatiotemporal variability in Arctic surface O3. We have integrated the Coupled Ocean-Atmosphere Response Experiment Gas transfer algorithm (COAREG) into the mesoscale meteorology and atmospheric chemistry model Polar-WRF-Chem (WRF) which introduces a dependence of O3 deposition on 10 physical and biogeochemical drivers of oceanic O3 deposition. We have also::::: Also, :: we:reduced the O3 deposition to sea ice and snow. Here, we evaluate the performance of WRF and the ::::: WRF ::: and CAMS reanalysis data against hourly-averaged surface O3 observations at 25 sites (latitudes > 60 oN)including the Arctic Summer Cloud Ocean Study (ASCOS) campaign observations. This is the first time such a coupled modelling system has been evaluated against hourly observations at Pan-Arctic sites to study the sensitivity of the deposition scheme to the magnitude and short-term ::::::::: magnitude ::: and : temporal variability in Arctic 15 surface O3 . We also analyze the impact of nudging:: on:::: the :::::::: deposition:::::::: scheme. ::: We::: find:::: that:: it:: is :::::::: important:: to:::::: nudge WRF to the synoptic conditions from the ECMWF ERA5 reanalysis data on simulated Arctic meteorology and comparison of observed and simulated O3concentrations : to:::::: ensure::::::: adequate::::::::::::: meteorological::::::::: conditions:: to::::::: evaluate:::::: surface::: O3. We show that the more mechanistic representation of O3 deposition over oceans and reduced snow/ice deposition improves simulated Arctic O3 mixing ratios both in terms of magnitude but also regarding observed temporal variability . Using the newly 20 implemented approach ::::::::: magnitude ::: and :::::::: temporal :::::::: variability ::::::::: compared :: to ::: the ::::::: constant :::::::: resistance ::::::::: approach. ::::: Using :::::::: COAREG, O3 deposition velocities have been simulated :: are : in the order of 0.01 cm s-1 compared to ∼0.05 cm s-1 in the constant surface uptake resistance approach. The simulated monthly-mean spatial variability in the mechanistic approach (0.01 to 0.018 cm s-1) expresses the sensitivity to chemical enhancement with dissolved iodide whereas the temporal variability (up to± 20% around the mean) expresses mainly differences in waterside turbulent transport. The bias for all observational :::: mean :::: bias ::: for :: 6 sites 25 above 70 oN reduced from -7.7 ::: -3.8 : ppb to 0.3 ppb with nudging and the revision to ocean and snow/ice deposition. Our study