06 Feb 2023
 | 06 Feb 2023

Modelling of tropospheric NO₂ using WRF-Chem with optimized temporal NOₓ emission profiles derived from in-situ observations – Comparisons to in-situ, satellite, and MAX-DOAS observations over central Europe

Leon Kuhn, Steffen Beirle, Vinod Kumar, Sergey Osipov, Andrea Pozzer, Tim Bösch, Rajesh Kumar, and Thomas Wagner

Abstract. We present a WRF-Chem simulation over central Europe with a high spatial resolution of 3 km × 3 km and a focus on nitrogen dioxide (NO₂). A regional emission inventory, issued by the German Environmental Agency, with a spatial resolution of 1 km × 1 km is used. We demonstrate, that by precise temporal modulation of the emission data (use of "temporal profiles"), significant improvement in model accuracy over existing simulations is achieved. Simulated NO₂ surface concentrations are compared to measurements from a total of 275 in-situ measurement stations in Germany, where the model was able to reproduce average noontime NO₂ concentrations with a bias of +0.9 % and R = 0.76. A comparison between modelled NO₂ vertical column densities (VCDs) and satellite observations from TROPOMI (TROPOspheric Monitoring Instrument) is conducted, where crucial aspects of the observation process, such as altitude-dependent NO₂ sensitivity as well as the influence of clouds and a priori assumptions of the retrieval, are taken into account. Simulations and satellite observations are shown to agree with a model bias of −6.6 % and R = 0.84 for monthly means. Lastly, simulated NO₂ concentration profiles are compared to profiles obtained from Multiaxis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of five European ground stations using the profile retrieval algorithms from the Mexican MAX-DOAS fit (MMF) and the Mainz Profile Algorithm (MAPA). For stations within Germany, biases of −5.9 % to +50.3 % were obtained when comparing average noontime NO₂ concentrations at different altitudes. Outside of Germany, where lower resolution emission data was used, biases of up to +78.6 % were observed. Overall, the study demonstrates that temporal modulation of emission data is crucial for modelling tropospheric NO₂ realistically.

Leon Kuhn et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Reviewer comments on egusphere-2022-1473', Anonymous Referee #2, 07 Feb 2023
  • RC2: 'Comment on egusphere-2022-1473', Anonymous Referee #3, 04 Jun 2023

Leon Kuhn et al.


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Short summary
NO₂ is an important air pollutant. It was observed that state of the art models for chemistry and transport show significant deviations in NO₂ abundance when compared to measurements. We use the model WRF-Chem for a 1-month simulation over central Europe and show that these deviations can be mostly resolved by precise temporal tuning of the emission data driving the model. In order to validate our results, they are compared to in-situ, satellite and MAX-DOAS measurements.