Air pollution is a major concern for the environment, human health and climate at scales spanning local to global. Air quality and the associated variability in pollutant concentrations are determined by pollutant emissions and atmospheric dynamical and chemical processes interacting across all scales. The NCAS Weather directorate conducts research on the dynamical and physical processes that determine the distribution of pollutants vertically (e.g. entrainment into and ventilation out of the boundary layer, deep convection) and horizontally (e.g. through advective processes) and their interactions with the regional- and synoptic-scale circulations (e.g. leading to long-range transport). Air quality modelling research focuses particularly on the representation of these processes in numerical models used for weather prediction, pollutant transport and climate studies. The scientific approaches require multi-pollutant multi-scale models that include a comprehensive description of atmospheric transport and mixing processes, along with detailed chemical interactions. A strong collaboration exists with model developers for the application and development of models.

On-going projects include the NCAS-led, NERC funded, Clean Air for London (ClearfLo) and EU FP7 Transport related Air Pollution and Health impacts - Integrated Methodologies for Assessing Particulate Matter (TRANSPHORM) projects. Results from high-resolution meteorological and air quality simulations (using the Weather Research and Forecasting (WRF) model and the Community Multiscale Air Quality (CMAQ) modelling system, respectively) are analysed to assess the current capability of the models to reproduce the key atmospheric processes that determine the variability of London’s air quality. The analysis makes use of data from extensive measurements of the meteorology, composition and particulate loading of London’s urban atmosphere, made at street level and at elevated sites (e.g. BT Tower) collected since early 2011. TRANSPHORM involves the use of regional models such as WRF/CMAQ driven by boundary conditions from global models to predict current and future (2020) particulate matter concentrations over Europe and the estimation of associated health impacts, bringing together the disciplines of weather, composition, climate and health.

 NCAS-Weather has also made important contributions to national and international strategic activities aiming to enhance air quality model development and performance, most notably the Defra Model Intercomparison Exercise (Defra MIE) and the Air Quality Model Evaluation International Initiative (AQMEII), consisting of more than 20 European and North American teams. Such activities underpin the continuous development of models.

Air quality modelling activities have provided specific information to stakeholders on the use of regional models for regulatory and policy applications. On-going projects include Environment Agency and Defra funded projects on the development of the CMAQ modelling system for UK applications.

Staff involved in this activity are Dr Charles Chemel and Prof Ranjeet Sokhi, University of Hertfordshire