Does an Increase in Air Quality Models’ Resolution Bring Surface Ozone Concentrations Closer to Reality?

Abstract

A persistent challenge for small-scale air quality modeling is the assessment of health impact and population exposure studies. Despite progress in computation and in the quality of model input (i.e., highresolution information on land use and emission patterns), the uncertainty associated with input parameters cannot be eliminated. The aim of this paper is to study different sources of uncertainty that affect model results as the resolution increases. Mesoscale chemistry transport simulations at different resolutions are used and modeled 0 3 concentrations are compared with surface measurements. The case study consists of CHIMERE model simulations over the city of Paris. It is shown that the principal source of noise in model results is the resolution of the input emission fluxes. The O 3 concentrations modeled with simulations forced by several horizontal resolutions of input emission data (from ⌬x ϭ 48 km to ⌬x ϭ 6 km) indicate that model results do not improve monotonously with resolution, but that after a certain point discrepancies become larger. Based on this result and as an alternative to the deterministic downscaling that resolves explicitly the finer scale (beyond the 1-km range), the authors propose a subgrid-scale approach that uses a statistical description of spatial scales finer than model resolution. As an example, the subgrid variability of modeled O 3 concentration has been quantified, when modeled dry deposition processes occur over subgrid surfaces (land use fractions). The implementation of this modified calculation gives access to subgrid fluxes and subgrid surface concentrations instead of the mean values provided by the commonly used model calculation.

Climate-forced air-quality modeling at the urban scale: sensitivity to model resolution, emissions and meteorology

“…Modeled meteorological fields are further interpolated over the 4 km-resolution IdF grid for the air-quality simulation. We note here, that in- terpolating the 0.44 • resolution meteorology over the 4 km resolution CHIMERE grid adds a source of uncertainty in modeled pollutant concentrations, but due to the flat topography of the area and as shown in previous research studies in the same region, increasing the resolution of the meteorological input does not improve model performance Valari and Menut, 2008). To study the impact of the resolution of the input meteorology here, we conduct a second sensitivity run where meteorological input stems from a WRF simulation using ERA40 reanalysis data over a finer resolution mesh with grid spacing of 0.11 • (ERA01) and compare with the ERA05 run.…”

“…Regarding urban ozone, there are plentiful studies on the effect of model resolution refinement with an overall tendency to show improvement of the model's quality when increasing resolution from about 30-50 to 4-12 km (Arunachalam et al, 2006;Cohan et al, 2006;Tie et al, 2010;Valari and Menut, 2008). On the other hand, reports are scarce for fine particles: Punger and West (2013) show that increasing the resolution from 36 to 12 km improved the 1 h daily maximum concentrations but not the daily average, Stroud et al (2011) reported better agreement of fine particles of organic origin with measurements from a modeling exercise at a 2.5 km resolution domain over a 15 km resolution domain, while Queen and Zhang (2008) also show improvement but their results include the effect of increasing the resolution of the meteorological input as well.…”

“…On the other hand, reports are scarce for fine particles: Punger and West (2013) show that increasing the resolution from 36 to 12 km improved the 1 h daily maximum concentrations but not the daily average, Stroud et al (2011) reported better agreement of fine particles of organic origin with measurements from a modeling exercise at a 2.5 km resolution domain over a 15 km resolution domain, while Queen and Zhang (2008) also show improvement but their results include the effect of increasing the resolution of the meteorological input as well. Valari and Menut (2008) showed that the impact of the resolution of emissions on modeled concentrations of ozone may be higher than the model resolution itself. This question has not yet been raised in the framework of climate-driven atmospheric composition modeling at the local scale.…”

“…Daily average ozone is better represented than daily maxima, highlighting model sensitivity to accumulated errors (Valari and Menut, 2008). Modeled peak concentrations are particularly sensitive to temperature compared to the daily averages as shown in Menut at al.…”

“…More recent studies have integrated advanced chemistry schemes capable of resolving the variability of pollutant concentrations at regional scale, which spans from several hours up to a few days, with chemistry transport models (CTMs) (Colette et al, 2012Knoche, 2006, 2007;Hogrefe et al, 2004;Katragkou et al, 2011;Kelly et al, 2012;Knowlton et al, 2004;Lam et al, 2011;Langner et al, 2005Langner et al, , 2012Nolte et al, 2008;Szopa and Hauglustaine, 2007;Tagaris et al, 2009;Zanis et al, 2011). Global models with a typical resolution of a few hundreds of kilometers and regional CTMs used at resolutions of a few tens of kilometers, and their parameterization of physical and chemical processes make them inadequate for modeling airquality at the urban scale (Cohan et al, 2006;Forkel and Knoche, 2007;Markakis et al, 2014;Sillman et al, 1990;Tie et al, 2010;Valari and Menut, 2008;Valin et al, 2011;Vautard et al, 2007).…”