Air quality simulations for London using a coupled regional-to-local modelling system

Abstract

Abstract. A coupled regional-to-local modelling system comprising a regional chemistry-climate model with 5 km horizontal resolution (EMEP4UK) and an urban dispersion and chemistry model with explicit road source emissions (ADMS-Urban) has been used to simulate air quality in 2012 across London. The study makes use of emission factors for NO x and NO 2 and non-exhaust emission rates of PM 10 and PM 2.5 which have been adjusted compared to standard factors to reflect real-world emissions, with increases in total emissions of around 30 % for these species. The performance of the coupled model and each of the two component models is assessed against measurements from background and near-road sites in London using a range of metrics concerning annual averages, high hourly average concentrations and diurnal cycles. The regional model shows good performance compared to measurements for background sites for these metrics, but under-predicts concentrations of all pollutants except O 3 at near-road sites due to the low resolution of input emissions and calculations. The coupled model shows good performance at both background and near-road sites, which is broadly comparable with that of the urban model that uses measured concentrations as regional background, except for PM 2.5 where the under-prediction of the regional model causes the coupled model to also under-predict concentrations. Using the coupled model, it is estimated that 13 % of the area of London exceeded the EU limit value of 40 µg m −3 for annual average NO 2 in 2012, whilst areas of exceedances of the annual average limit values of 40 and 25 µg m −3 for PM 10 and PM 2.5 respectively were negligible.

CALIOPE-Urban v1.0: Coupling R-LINE with a mesoscale air quality modelling system for urban air quality forecasts over Barcelona city (Spain)

“…Urban air quality models such as SIRANE (Soulhac et al, 2011) have already implemented vertical mixing depending on local meteorology. In this study, we will show that this process may be relevant and explain some systematic errors found in the literature: nighttime NO 2 concentration values tend to be overestimated and afternoon values tend to be underestimated in traffic areas (e.g., Hood et al, 2018). Further efforts are necessary to explicitly resolve processes happening among scales and to correct these biases in the mentioned periods of the day.…”

“…In order to overcome these limitations, coupling regional and urban scale models has been recently found to be successful in some cities. Hood et al (2018) coupled a regional climate-chemistry model with 5 km horizontal resolution EMEP4UKwith the fine-scale model ADMS-URBAN to simulate air quality over London in 2012. They compared the coupled system results with the regional and the fine-scale models run separately.…”

“…Kochanski et al (2015) used a simplified CFD (QUIC) in combination with WRF to estimate wind conditions at street level. Hood et al (2018) estimate an urban canopy flow field at the same resolution of the regional model. This calculation is based on the variation of surface roughness within the city.…”

A hybrid model approach for estimating health burden from NO2 in megacities in China: a case study in Guangzhou

“…The challenge of high spatial resolution air pollution modelling has driven integrated data and modelling approaches (Johnson et al 2010, Beevers et al 2012, Hao et al 2016, Yang et al 2017, Hood et al 2018, Xue et al 2019. For megacities of large area like Guangzhou, without additional monitoring data, our solution for simulation of an NO 2 concentration map has been to derive a hybrid modelling approach that uses a virtual network of receptor locations for dispersion and LUR modelling.…”

Interactive comment on “CALIOPE-Urban v1.0: Coupling R-LINE with a mesoscale air quality modelling system for urban air quality forecasts over Barcelona city (Spain)” by Jaime Benavides et al.

“…In order to overcome these limitations, coupling the regional and urban scales offline by downscaling the regional model using a dispersion kernel has been successfully applied in some cities Moussafir et al, 2014;Isakov et al, 2014;Jensen et al, 2017;Maiheu et al, 2017;Kim et al, 2018;Hood et al, 2018;Fagerli et al, 2019). For instance, Hood et al (2018) coupled a regional climate-chemistry model with 5 km horizontal resolution (EMEP4UK) with the fine-scale model ADMS-URBAN to simulate air quality over London in 2012.…”