Dry deposition is an important removal mechanism for tropospheric ozone (O3). Its deposition to oceans is generally represented in atmospheric chemistry transport models using constant surface uptake resistances. However, observations show quite large spatiotemporal variability expressing differences in solubility, waterside turbulence and O3 reacting with iodide and dissolved organic matter. We hypothesize that for the Arctic O3 deposition is overestimated with consequences for background concentrations and lifetime of O3 also due to changes in long-range transport of O3 and its precursors. These are focal points of a project on observing and modelling of Arctic climate-active trace gas exchange as a contribution to the MOSAiC observational campaign with the icebreaker Polarstern being trapped in the Arctic sea-ice for ~1 year.
We have coupled the Coupled Ocean-Atmosphere Response Experiment Gas transfer algorithm (COAREG) to the mesoscale meteorology and atmospheric chemistry model Polar-WRF-Chem (PWRF-C). This includes a further development including a two-layer scheme for O3 deposition to oceans and coupling to recently updated ocean water composition databases. We have also reduced the deposition of O3 to sea ice based on a previous study of snow-ice O3 deposition.
In this study, we evaluate the performance of PWRF-C with hourly-averaged surface O3 measurements above 60 ºN and with O3 sondes. We show that the more mechanistic representation of O3 deposition over oceans and strongly reduced deposition over snow and ice results in improved simulated Arctic O3 mixing ratios. We found that it is important to nudge PWRF-C to the ECMWF ERA-Interim wind fields which secures a fair comparison of the model with measurements regarding their footprint. Our study indicates that representation of ocean and sea-ice O3 deposition in atmospheric chemistry models must be revised to improve the representation of Arctic O3 concentrations and chemistry.
How to cite: Barten, S., Ganzeveld, L., Steeneveld, G.-J., and Krol, M.: Mechanistic Ocean-Atmosphere exchange of trace gases in Polar-WRF-Chem: Implications for Arctic tropospheric ozone, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-144, https://doi.org/10.5194/ems2022-144, 2022.
