CERC — Environmental Software and Services

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MAQS (formerly ADMS-Urban RML)

Multi-Model Air Quality System

What is MAQS?

MAQS (formerly ADMS-Urban RML) enables air qualtiy modelling to be undertaken at a wide range of scales from street scale (metres) to regional (hundreds of kilometres or more). The system combines ADMS-Urban with an innovative regional model link (RML) to provide automated coupling of ADMS-Urban with output data from regional meteorological and air quality models. Supported model formats are WRF for meteorological data and CMAQ, CAMx, CHIMERE, EMEP4UK or WRF-Chem for air quality data. The output from MAQS contains predictions of pollutant concentrations for an urban area, taking into account both regional and local pollutant transport and chemistry effects.

MAQS runs on Linux and comprises:

  • ADMS-Urban dispersion model
  • tools to process the regional model data
  • software to automate running these components

The system is also supplied with an ADMS-Urban Windows interface for generating input files containing local emissions and output point locations for MAQS.

Typical applications of MAQS include:

  • developing and testing the impact of regional and local air quality management policies on pollutant concentrations throughout a complex urban area;
  • exposure assessments;
  • provision of detailed street-scale air quality forecasts for an urban area in combination with a regional scale forecast for surrounding rural area.

Who uses MAQS?

Image of Hong Kong NO2 forecast concentration contours for 2017

Forecast NO2 concentrations contours from CMAQ (left) and MAQS (right) for the main urban areas of Hong Kong and Kowloon, for 3 pm local time on 13th October 2017.


Image of West Midlands NO2 and PM2.5 concentration contours

Annual average NO2 and PM2.5 concentrations for the West Midlands (UK), modelled at street scale resolution using MAQS as part of the WM-Air project. From Zhong et al. (2022).

MAQS is for current users of regional air dispersion models who wish to increase the resolution of their modelling over urban areas to take account of street-scale concentration gradients in a computationally efficient way, and for users of ADMS-Urban who wish to take into account spatially-varying meteorology and background concentrations from regional modelling. The design of the system allows the regional modelling and the local modelling to be performed separately, facilitating collaborations between regional and local modelling specialists and allowing a single set of regional modelling data to be used to test many local modelling scenarios.

Pioneering uses of MAQS include:

  • MAQS has been set up to model the Hong Kong Special Administrative Region for the Hong Kong Environmental Protection Department. Regional model data was taken from the CAMx model run by researchers from the Hong Kong University of Science and Technology (HKUST). The PRAISE-HK project is generating daily street-scale forecasts for Hong Kong using MAQS driven by regional CMAQ forecasting.
  • Researchers at the University of Edinburgh’s Contemporary Climate group use MAQS with the EMEP4UK regional model to investigate the effects of future climate scenarios on local air quality in London and across the UK.
  • CERC and researchers from University of Birmingham collaborated in the WM-Air project, which used MAQS to model street-scale air quality in the West Midlands region of the UK.
  • Under the MAQS-Health project, CERC developed MAQS (formerly ADMS-Urban RML) to support a ‘generic’ input format for meteorological and concentration data, allowing data from other regional models to be converted for use in the system. Partners from the Universities of Edinburgh, Birmingham and Lancaster and the UK Met Office have tested the system with a range of regional models and domains.
  • CERC have used MAQS to model the Republic of Ireland for the Irish Environmental Protection Agency, with 20 m output contour resolution across the whole country and 5 m resolution within main cities.
  • CERC’s partners in France, NUMTECH, are planning to combine their experience of using ADMS-Urban and the regional model CHIMERE by using MAQS to improve modelling of complex urban environments in France.

Why use MAQS?

Image of Scotload NOx concentration contours for 2018

Annual average NOx concentrations for Scotland in 2018, modelling with the MAQS-Health coupled system led by the University of Edinburgh.


Image of Northern Ireland NO2 concentration contours for 2020

March 2020 annual average NO2 concentrations for Northern Ireland modelled using the MAQS-Health coupled system by the University of Lancaster.

Coupling the local model ADMS-Urban within a regional model using MAQS allows both the resolution of high concentration gradients close to a source, and the accurate representation of transport and chemistry over larger spatial and temporal scales. MAQS combines the regional and local concentrations in such a way as to minimise double-counting of emissions, while remaining computationally efficient and user-friendly.

The principal features of MAQS are:

  • An automated control system with logging of progress to file and screen;
  • Option for use of the GNU Parallel approach for distributing runs across multiple machines;
  • Compatibility with CMAQ, CAMx, CHIMERE, EMEP4UK and WRF-Chem regional air pollution models, with potential for extension to other regional models;
  • Automatic division of a large nesting domain into separate runs for each regional model grid cell, with appropriate local meteorology from the meso-scale meteorological model and regional background concentrations;
  • Flexibility regarding the size and shape of the nesting domain;
  • No requirement to re-run the regional air quality or meteorological models;
  • Inclusion of advanced modelling techniques for urban areas, such as street canyon and urban canopy flow field calculations, through the use of ADMS-Urban.

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