C044-0007
Mechanistic Ocean-Atmosphere exchange of trace gases in Polar-WRF-Chem: Implications for Arctic surface ozone
Mechanistic Ocean-Atmosphere exchange of trace gases in Polar-WRF-Chem: Implications for Arctic surface ozone
Monday, 14 December 2020
Poster
Abstract:
The Arctic budget and concentrations of ozone (O3), being both a pollutant and import greenhouse gas, is sensitive to the representation of deposition to snow and ice as well the Arctic ocean also due to the generally prevailing suppressed mixing conditions and slow chemistry. This large sensitivity is generally not anticipated also based on the few observations of very small deposition rates in the Arctic. Surface deposition is generally being represented in large-scale models to assess Arctic composition and atmospheric chemistry using fixed small sea-ice and ocean water uptake rates ignoring potentially important dependencies of this uptake process on physical and biogeochemical drivers. The MOSAiC campaign also included an explicit activity to collect O3 flux observations over sea-ice and the Arctic ocean which should strongly enhance the insights in the mechanisms and magnitude of Arctic O3 deposition.
We have coupled the Coupled Ocean-Atmosphere Response Experiment Gas transfer algorithm (COAREG) to the mesoscale meteorology and atmospheric chemistry model Polar-WRF-Chem (WRF). This replaces the constant surface resistance approach in WRF with a two-layer scheme for O3 deposition to oceans and introduces a dependence of Arctic O3 deposition on ocean mixing conditions and biogeochemical composition. This coupling of COAREG to WRF is also motivated by further application of this modelling system to support analysis of the 1-year MOSAiC observations on Arctic ocean and sea-ice atmosphere fluxes of O3 and other climate-active trace gases.
Here, we evaluate the performance of WRF against hourly-averaged surface O3 observations above 60 ºN. 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. We find that it is important to nudge WRF to the ECMWF ERA5 synoptic conditions which secures a fair model evaluation regarding their footprint. Our study further corroborates the findings of previous global scale ocean O3 deposition studies and recommends that the representation of ocean and sea-ice O3 deposition in atmospheric chemistry models must be revised to improve also the representation of Arctic O3 concentrations and chemistry.
We have coupled the Coupled Ocean-Atmosphere Response Experiment Gas transfer algorithm (COAREG) to the mesoscale meteorology and atmospheric chemistry model Polar-WRF-Chem (WRF). This replaces the constant surface resistance approach in WRF with a two-layer scheme for O3 deposition to oceans and introduces a dependence of Arctic O3 deposition on ocean mixing conditions and biogeochemical composition. This coupling of COAREG to WRF is also motivated by further application of this modelling system to support analysis of the 1-year MOSAiC observations on Arctic ocean and sea-ice atmosphere fluxes of O3 and other climate-active trace gases.
Here, we evaluate the performance of WRF against hourly-averaged surface O3 observations above 60 ºN. 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. We find that it is important to nudge WRF to the ECMWF ERA5 synoptic conditions which secures a fair model evaluation regarding their footprint. Our study further corroborates the findings of previous global scale ocean O3 deposition studies and recommends that the representation of ocean and sea-ice O3 deposition in atmospheric chemistry models must be revised to improve also the representation of Arctic O3 concentrations and chemistry.