ADMS-Urban RML - Innovative Automated System for Nesting ADMS-Urban

The main components of the ADMS-Urban RML system are the ADMS-Urban local dispersion model, Run Managersoftware for distributing ADMS-Urban runs across multiple machines and the ADMS-Urban RML Controller, which consists of a graphical user interface, control program and five utility programs.

Typical applications of the ADMS-Urban RML include include:

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

The ADMS-Urban RML system 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 the ADMS-Urban Regional Model Link include:

• The ADMS-Urban RML 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). HKUST hope to extend their existing CMAQ and CAMx regional model air quality forecasting system to predict roadside concentrations by incorporating the ADMS-Urban RML system.
• Researchers at the University of Edinburgh’s Contemporary Climate group use the ADMS-Urban RML with the EMEP4UK regional model to investigate the effects of future climate scenarios on local air quality in London and across the UK.
• CERC’s partners in France, NUMTECH, are planning to combine their experience of using ADMS-Urban and the regional model CHIMERE by using the ADMS-Urban RML system to improve modelling of complex urban environments in France.

Nesting the local model ADMS-Urban within a regional model using the ADMS-Urban Regional Model Link 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. The ADMS-Urban RML system 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 the ADMS-Urban RML system are:

• A user-friendly graphical interface
• An automated control system with logging of progress to file and screen
• Integration with CERC’s Run Manager software for distributing ADMS-Urban runs across multiple machines
• Compatibility with CMAQ, CAMx and EMEP4UK 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 WRF meso-scale model and 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

Meso-scale Meteorological Model Data

The ADMS-Urban RML system uses meteorological data output files from the WRF meso-scale model. These files should contain the same data as used to run the regional air quality model, to ensure consistency between the regional and local components of the system. The ADMS-Urban RML Controller automatically identifies the correct data file for each hour of the modelling period following a user-defined date- and time-dependent naming convention.

Regional Model Concentration Data

At present the ADMS-Urban RML is compatible with output files from the CMAQ, CAMx (converted to I/O API) and EMEP4UK regional air quality models. The regional model output data should cover the required RML modelling domain with a buffer of one cell in each direction. The regional model grid must be regular in a projected coordinate system with units of metres. As the more detailed chemistry schemes used for regional modelling include a larger number of chemical species than are typically used in ADMS-Urban, a species map file is used to define how the regional model and ADMS-Urban pollutant species are related, including any required unit conversion factors. The ADMS-Urban RML system is designed to be extendable to other regional models. Please contact CERC if you would like to use the ADMS-Urban RML system with output from a different regional model.

Emissions

NO2 emissions data visualised in the ADMS Mapper

In addition to the standard emissions data which is required to model an urban area using ADMS-Urban, for the ADMS-Urban RML system, gridded emissions data consistent with that used in the regional model must be processed in order to obtain valid nesting background concentrations. Both the total emission rates and the time-variation of emissions should be matched as closely as possible to the regional model equivalents.

Local Modelling Parameters

ADMS-Urban model parameter files must be set up containing local source emissions, for example explicitly-modelled road sources, and specification of the required output locations and pollutant species.

Model Output Data

The output files from the ADMS-Urban RML system contain hourly concentrations at each output location in the portablenetCDF format. The system is also supplied with a utility to extract statistics such as percentiles to ADMS-format text files, which can then be used in the standard ADMS-Urban contour plotting utilities and the MyAir Model Evaluation Toolkit.

As with ADMS-Urban, intelligent gridding can be included in the ADMS-Urban RML system in order to create high-resolution contour plots of concentrations.

The ADMS-Urban RML Controller interface allows the user to enter the data required for the modelling in a straightforward manner. The inputs are divided into four broad categories, with individual sections covering more specific aspects of the run. To set up a model run, the user simply works through the screens entering the relevant data or referencing external data files.

The user can define a template file to set custom default values for any or all system parameters which will then be applied to new ADMS-Urban RML system runs.

The initial concept of nesting ADMS-Urban in the regional model CMAQ was developed by CERC and published as Stocker et al. (2012). Further development for nesting in the EMEP4UK model was carried out in collaboration with the Centre for Ecology and Hydrology and supported by the UK Department for the Environment, Food and Rural Affairs.

Example frequency scatter plots comparing modelled and observed NO2 hourly concentrations from the ADMS-Urban RML (left) and CAMx (right)

The development of the automated ADMS-Urban RML system was carried out under a project for the Hong Kong Environmental Protection Department, in collaboration with researchers from the Hong Kong University of Science and Technology.

Details of verification studies using the ADMS-Urban RML system can be found on the Model validation pages.

User Support
The ADMS-Urban RML system is supplied with an in-depth user guide (please refer to the User Guides page) that details all user inputs and outputs, and includes a number of step-by-step worked examples. The user guide also gives a technical description of the system.

An annual maintenance contract provides support for users; this includes:

• maintenance model upgrades,
• use of the helpdesk by e-mail, phone, fax or post,
• attendance at the annual ADMS-Urban user group meeting,
• receipt of the ADMS-Urban newsletter twice a year, and
• access to the password-protected user area.

If you would like any additional information regarding the ADMS-Urban RML system, including details of available training courses, please contact CERC.