Defra are undertaking a project to investigate and demonstrate how the Community Multi-Scale Air Quality Modelling System (CMAQ)  might meet Defra’s needs with respect to the national modelling and assessment of UK air quality policies and to develop a configuration optimised for those needs in the UK (CMAQ-UK). The project is a collaboration between Ricardo Energy & Environment, Imperial College and the University of Hertfordshire.

The project involves the development and evaluation of the CMAQ model optimised in a way that will best meet Defra’s future modelling and assessment needs. The overall work programme is being delivered in two phases.

The first phase undertaken in 2011/2012 consisted of 3 main objectives these were:

  • Assessing the potential role to be played by CMAQ in addressing Defra’s main evidence needs associated with different air quality policy drivers
  • Developing an initial optimised configuration of CMAQ to meet Defra’s evidence needs
  • Collaboration with the wider CMAQ community

Example of CMAQ output

Image above: Example of the application of CMAQ in Health Impact Assessments
(i) Number of days when daily maximum 8-hour average O3 concentration > 100 ug m-3 during the June to July period in 2006, (ii) number of deaths brought forward due to short-term exposure to O3 with a threshold values of 35 ppb for the June – July 2006 period

Phase 2 will continue in 2013/14 with:

  • Targeted improvements to CMAQ-UK focusing on the key input data for CMAQ including meteorology, emissions and boundary conditions.
  • A demonstration of using CMAQ-UK to assess compliance with regulatory obligations for 2020. This is a key date for achieving the 2020 PM2.5 exposure reduction target and limit values relative to 2010 as required by EC Directive 2008/50/EC. This will be extended to including gas species and deposition to demonstrate the strengths of using a “one atmosphere” model. The demonstration will be based on three years for 2010 (2009-2011) and three for 2020 (2019-2021) this will provide a robust evaluation taking into account inter-annual variation in meteorology and emissions.
  • The development of tools to evaluate a full range of compliance metrics and that can be used for providing a comparison with existing models used by Defra.
  • Evaluation of the potential use of the decision support tools available within CMAQ.
  • Evaluation of the Secondary Organic Aerosol chemistry scheme used in CMAQ in relation to that developed in the UK from the Master Chemical Mechanism.
  • Continuing collaboration with the wider CMAQ community

For further information contact Andrea Fraser at Ricardo Energy & Environment