Implementation and evaluation of updated photolysis rates in the EMEP MSC-W chemistry-transport model using Cloud- J v7.3e

van Caspel, Willem E.; Simpson, David; Jonson, Jan Eiof; Benedictow, Anna M. K.; Ge, Yao; di Sarra, Alcide; Pace, Giandomenico; Vieno, Massimo; Walker, Hannah L.; Heal, Mathew R.

The present work describes the implementation of the state of the art Cloud-inline-formulaJ v7.3 photolysis rate calculation code in the EMEP MSC-W chemistry-transport model. Cloud-inline-formulaJ calculates photolysis rates and accounts for cloud and aerosol optical properties at model run time, replacing the old system based on tabulated values. The performance of Cloud-inline-formulaJ is evaluated against aerial photolysis rate observations made over the Pacific Ocean and against surface observations from three measurement sites in Europe. Numerical experiments are performed to investigate the sensitivity of the calculated photolysis rates to the spatial and temporal model resolution, input meteorology model, simulated ozone column, and cloud effect parameterization. These experiments indicate that the calculated photolysis rates are most sensitive to the choice of input meteorology model and cloud effect parameterization while also showing that surface ozone photolysis rates can vary by up to 20 % due to daily variations in total ozone column. Further analysis investigates the impact of Cloud-inline-formulaJ on the oxidizing capacity of the troposphere, aerosol–photolysis interactions, and surface air quality predictions. Results find that the annual mean mass-weighted tropospheric hydroxyl concentration is increased by 26 %, while the photolytic impact of aerosols is mostly limited to large tropical biomass-burning regions. Overall, Cloud-inline-formulaJ represents a major improvement over the tabulated system, leading to improved model performance for predicting carbon monoxide and daily maximum ozone surface concentrations.



van Caspel, Willem E. / Simpson, David / Jonson, Jan Eiof / et al: Implementation and evaluation of updated photolysis rates in the EMEP MSC-W chemistry-transport model using Cloud-J v7.3e. 2023. Copernicus Publications.


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Rechteinhaber: Willem E. van Caspel et al.

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