Investigating the impact of HARMONIE-WINS50 (cy43) and LOTOS-EUROS (v2.2.002) coupling on NO₂ concentrations in The Netherlands

Abstract. Meteorological fields calculated by Numerical Weather Prediction (NWP) Models drive offline Chemical Trans port Models (CTM) to solve the transport, chemical reactions, and atmospheric interaction over the geographical domain of interest. In this way, forecasts and (re-)analyses provided by NWP can be used for air quality forecasting, climate modeling, and environmental studies. The more precise the meteorological input data represents the atmospheric dynamics, the better the CTM represents pollutant transport, mixing, and the subsequent impact on surface air quality. HARMONIE (HIRLAM ALADIN Research on Mesoscale Operational NWP in Euromed) is a state-of-the-art non-hydrostatic NWP community model used at several European weather agencies to forecast weather at the local and/or regional scale. In this work, the HARMONIE WINS50 (cycle 43 cy43) reanalysis data set at a resolution of 0.025° × 0.025° covering an area surrounding the North Sea for the years 2019–2021 was offline coupled to the state-of-the-art model LOTOS-EUROS (v2.2.002), which is CTM that is one of the members of the Copernicus Atmosphere Monitoring Service (CAMS) ensemble of CTMs that is used to produce operational air quality forecasts over Europe and at a higher resolution also over the Netherlands. The impact on simulated NO₂ concentrations of using meteorological fields from HARMONIE in LOTOS-EUROS compared to the use of fields from ECMWF (here used at 0.7° ×0.7°) is evaluated against ground-level sensors and TROPOMI tropospheric NO₂ vertical columns. Furthermore, the difference between crucial meteorological input parameters such as the boundary layer height and the vertical diffusion coefficient between the hydrostatic (ECMWF) and non-hydrostatic (HARMONIE) model fields is studied, and the vertical profiles of temperature, humidity, and wind are evaluated against meteorological vertical profile observations at Cabauw in The Netherlands. The results of these first evaluations of the LOTOS-EUROS model performance in both configurations are used to investigate current uncertainties in air quality forecasting in relation to driving meteorological parameters and to assess the potential for improvements in high-resolution air quality forecasting episodes based on the HARMONIE NWP model.