A risk based application of the regional model CMAQ to policy decisions

Özet

A risk based approach to assessing compliance with EU limit values is described, using the advancedchemical transport model CMAQ to determine the regional component of NO2 and particulate matterunder various conditions over the UK. A new air quality data analysis retrieval tool AirDART is used toextract concentrations for selected areas of the country. Roadside concentrations in a street canyon arethen calculated using a dispersion model. The two model calculations need to be combined to obtainconcentrations in future years assuming appropriate changes in emission. To merge the local andregional contributions exactly requires assumptions regarding parameterisations and is computationallyexpensive. From a risk based viewpoint not every possible condition need be considered in order to makepolicy decisions. Instead future trends under typical conditions are estimated, allowing the direct effectof local action plans and of national measures to be assessed. The approach is applied to London, thisbeing a worst case UK example, to demonstrate the procedure.