Downscaling of air pollutants in Europe using uEMEP_v6

Qing Mu,Hilde Fagerli,Eivind Grøtting Wærsted,Bruce Rolstad Denby

doi:10.5194/gmd-15-449-2022

Qing Mu, Hilde Fagerli + Show 2 more

Open Access

https://doi.org/10.5194/gmd-15-449-2022

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Abstract

Abstract. The air quality downscaling model uEMEP and its combination with the EMEP MSC-W chemical transport model are used here to achieve high-resolution air quality modelling at street level in Europe. By using publicly available proxy data, this uEMEP–EMEP modelling system is applied to calculate annual mean NO2, PM2.5, PM10, and O3 concentrations for all of Europe down to 100 m resolution and is validated against all available AIRBASE monitoring stations in Europe at 25 m resolution. Downscaling is carried out on annual mean concentrations, requiring special attention to non-linear processes, such as NO2 chemistry for which frequency distributions are applied to better represent the non-linear NO2 chemistry. The downscaling shows significant improvement in NO2 concentrations for which the spatial correlation has been doubled for most countries and bias reduced from −46 % to −18 % for all stations in Europe. The downscaling of PM2.5 and PM10 does not show improvement in spatial correlation but does reduce the overall bias in the European calculations from −21 % to −11 % and from −39 % to −30 % for PM2.5 and PM10, respectively. There is improved spatial correlation in most countries after downscaling of O3 and a reduced positive bias of O3 concentrations from +16 % to +11 %. Sensitivity tests in Norway show that improvements in the emission and emission proxy data used for the downscaling can significantly improve both the NO2 and PM results. The downscaling development opens the way for improved exposure estimates, improved assessment of emissions, and detailed calculations of source contributions to exceedances in a consistent way for all of Europe at high resolution.

Highlights

The EMEP Meteorological Synthesizing Centre – West (EMEP MSC-W) at the Norwegian Meteorological Institute has been developing and implementing a downscaling methodology to enhance the capabilities of the EMEP MSCW chemical transport model (Simpson et al, 2012, 2020)
To test the impact of more realistic spatial distributions of emissions, the emission and emission proxy data used in Norway are replaced in the EMEP model and uEMEP calculations with the emission data currently used in the national air quality forecasting in Norway
(2) The non-exhaust road dust emissions are calculated with the NORTRIP model (Denby et al, 2013a, b), which are significantly larger than the current national estimates reported for Norway

Summary

Introduction

The EMEP Meteorological Synthesizing Centre – West (EMEP MSC-W) at the Norwegian Meteorological Institute has been developing and implementing a downscaling methodology to enhance the capabilities of the EMEP MSCW chemical transport model (Simpson et al, 2012, 2020) (hereafter the EMEP model) This downscaling model is known as uEMEP (urban EMEP) and can achieve highresolution air quality modelling down to 100 m for entire countries (Denby et al, 2020). Since uEMEP has been further developed and operationally implemented in the Norwegian Air Quality Forecasting System (Miljodirektoratet, 2020b) as well as providing air quality data, maps, and information to Norwegian municipalities through the Air Quality Expert Service (Miljodirektoratet, 2020a) These model applications and validations are described in detail in Denby et al (2020)

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