The influence of model spatial resolution on simulated ozone and fine particulate matter for Europe: implications for health impact assessments

Abstract

Abstract. We examine the impact of model horizontal resolution on simulated concentrations of surface ozone (O 3 ) and particulate matter less than 2.5 µm in diameter (PM 2.5 ), and the associated health impacts over Europe, using the HadGEM3-UKCA chemistry-climate model to simulate pollutant concentrations at a coarse (∼ 140 km) and a finer (∼ 50 km) resolution. The attributable fraction (AF) of total mortality due to long-term exposure to warm season daily maximum 8 h running mean (MDA8) O 3 and annual-average PM 2.5 concentrations is then calculated for each European country using pollutant concentrations simulated at each resolution. Our results highlight a seasonal variation in simulated O 3 and PM 2.5 differences between the two model resolutions in Europe. Compared to the finer resolution results, simulated European O 3 concentrations at the coarse resolution are higher on average in winter and spring (∼ 10 and ∼ 6 %, respectively). In contrast, simulated O 3 concentrations at the coarse resolution are lower in summer and autumn (∼ −1 and ∼ −4 %, respectively). These differences may be partly explained by differences in nitrogen dioxide (NO 2 ) concentrations simulated at the two resolutions. Compared to O 3 , we find the opposite seasonality in simulated PM 2.5 differences between the two resolutions. In winter and spring, simulated PM 2.5 concentrations are lower at the coarse compared to the finer resolution (∼ −8 and ∼ −6 %, respectively) but higher in summer and autumn (∼ 29 and ∼ 8 %, respectively). Simulated PM 2.5 values are also mostly related to differences in convective rainfall between the two resolutions for all seasons. These differences between the two resolutions exhibit clear spatial patterns for both pollutants that vary by season, and exert a strong influence on country to country variations in estimated AF for the two resolutions. Warm season MDA8 O 3 levels are higher in most of southern Europe, but lower in areas of northern and eastern Europe when simulated at the coarse resolution compared to the finer resolution. Annual-average PM 2.5 concentrations are higher across most of northern and eastern Europe but lower over parts of southwest Europe at the coarse compared to the finer resolution. Across Europe, differences in the AF associated with long-term exposure to population-weighted MDA8 O 3 range between −0.9 and +2.6 % (largest positive differences in southern Europe), while differences in the AF associated with long-term exposure to populationweighted annual mean PM 2.5 range from −4.7 to +2.8 % (largest positive differences in eastern Europe) of the total mortality. Therefore this study, with its unique focus on Europe, demonstrates that health impact assessments calculated using modelled pollutant concentrations, are sensitive to a change in model resolution by up to ∼ ±5 % of the total mortality across Europe.

Influence of spatial resolution on population PM2.5 exposure and health impacts

“…In contrast to other studies, Thompson et al (2014) evaluated health impacts using 4-, 12-, and 36-km resolutions and came to a conclusion that mortality attributable to PM 2.5 exposure is not sensitive to resolution when uncertainties are considered. A possible reason for this may be that the range of resolutions was relatively small compared with other studies (Fenech et al 2018).…”

“…Mortality attributable to PM 2.5 got smaller as resolution got coarser. Fenech et al (2018) used concentrations modelled with HadGEM3-UKCA chemistry-climate model at ca.140-km and ca.50-km resolutions to study health impacts of PM 2.5 in Europe and found that total mortality estimates are sensitive to a model resolution by up to ± 5% across Europe. Li et al (2016) used both air quality modelled (GEOS-Chem) and regridded concentrations at various resolutions (0.5 × 0.66°, 1 × 1.25°, 2 × 2.5°, and 4 × 5°) to estimate health impacts over the USA.…”

TM5-FASST: a global atmospheric source–receptor model for rapid impact analysis of emission changes on air quality and short-lived climate pollutants

“…We did not perform dedicated perturbation simulations on CH 4 as an O 3 precursor, but we implemented TM5 results obtained in the frame of the first phase of the Hemispheric Transport of Air Pollutants (HTAP1) assessment Fiore et al, 2008). In one of the prescribed experiment set-ups, models evaluated how surface ozone levels respond when the global steady-state CH 4 concentration decreases by 20 % from 1760 ppbv (the global mean CH 4 concentration in the year 2000) to 1408 ppbv.…”

Analysis of summer O<sub>3</sub> in the Madrid air basin with the LOTOS-EUROS chemical transport model

“…As shown in Table 1, two major aspects were modified in the set of five configurations: the meteorological input data and the vertical structure of the model. We fed LOTOS-EUROS with operational data from the reanalysis of the European Centre for Medium-Range Weather Forecast (ECMWF) model (Flemming et al, 2009) retrieved with a spatial resolution of 7 km × 7 km. A second meteorological gridded dataset was obtained with the Weather Research and Forecasting Model (WRF; Skamarock et al, 2008) with a resolution of 1 km × 1 km over a square domain of side 220 km centred on the city of Madrid (Fig.…”