Providing high-quality meteorological data is a key requirement for undertaking robust and defensible air quality modelling. RapidAir has been designed to enable users to quickly process and undertake quality assurance (gap filling using the United States Environmental Protection Agency (USEPA) methodology).
Default RapidMet users are provided with 3 years of meteorological files relevant to their study area. Specialist RapidMet users have access to tools that enable the processing and quality assurance of meteorological data available from a wide range of data sources, including respected open data sources such as those provided by the US National Oceanic and Atmospheric Administration. Once the data has been processed, wind and turbulence profiles are estimated based on the approximated stability of the atmospheric boundary layer.
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RapidEMS
Traffic emissions module
The RapidEMS module enables the rapid calculation of emissions rates for a range of key pollutants – including oxides of nitrogen (NOx), particulate matter with a diameter of less than 10 microns or 2.5 microns (PM10 and PM2.5 respectively) and carbon dioxide (CO2) – for specific years, road types (e.g motorways, urban), vehicle speeds and fleet composition. The default version of RapidEMS uses COPERT coefficients. In the UK, RapidEMS closely aligns with the latest version of the Department for Environment, Food and Rural Affairs’ (Defra) Emissions Factors Toolkit.
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RapidAir
Roads Dispersion Module
RapidAir is based on AERMOD, the USEPA’s recommended dispersion model for traffic emission sources. It is a steady-state dispersion model, in which pollutants are assumed to disperse away from their source in a plume with a Gaussian concentration profile in both directions perpendicular to the plume centreline.
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Canyons
Street canyon model and allocator
In built-up urban areas, air pollution can become trapped in street canyons – streets surrounded by tall buildings. As such, the impacts of canyons are important elements of any robust air quality modelling system. Street canyon models range from complex computational fluid dynamic (CFD) models to simpler empirical (such as the USEPA STREET box-model and semi-empirical models (such as the Danish Operational Street Pollution Model (OSPM)). RapidAir includes a canyon module based on the AEOLIUS system developed by the UK Met Office.
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