The application of Models-3 in national policy Samantha Baker Air and Environment Quality Division, Defra

Value of air quality modelling in policy development To provide a quantitative link between pollutant emissions at one or many locations, and the resulting concentrations or deposition experienced by humans or the environment, which is being protected. This allows changes in impact resulting from hypothetical changes in emissions to be readily evaluated.

Why use air quality modelling for policy development? To establish the current picture (compliance with legal obligations, or calculate baseline to compare future scenarios against) To establish future scenarios under business as usual (assess progress towards future legislative targets) To establish future scenarios that go beyond business as usual (assess impact of a range of potential abatement strategies to inform a negotiating position, to meet future legislative targets, or effects of proposed development)

Conflicting requirements in using modelling for policy applications Need to have a reasonable turn around time for scenario runs, especially during negotiating periods Need to have confidence in the model predictions - must believe that the model output is an accurate representation of what is currently happening and what will happen in the future – best science

Legislative drivers Air Quality Framework Directive and its Daughter Directives Clean Air For Europe National Emission Ceilings Directive UNECE Gothenburg Protocol IPPC, LCPD National Air Quality Strategy

AEQ7 contracts Modelling concentrations and deposition of long range air pollutants to develop and apply UK scale models for the deposition and concentration of a range of long range air pollutants including S and N compounds The UK Application of the EMEP model to develop and test a mesoscale version of the Unified EMEP Eulerian model for use in the UK at a 5km resolution The UK Application of Eulerian models at fine spatial resolution to investigate the use of state of the art Eulerian models, including Models-3, as possible future replacements for FRAME, the current Lagrangian model used to predict S and N deposition in the UK

WP1- Initial assessment Installation of operating versions of Models-3 and other state of the art Eulerian models Provision of high quality UK meteorology for operation of the models Verification of the atmospheric chemistry components of the models Comparison of the transport processes in the models with other models

WP2 - Implementation across the UK Successful implementation of models at a fine spatial scale (between 1 and 5km) in the UK Connection of models to a continental wide model domain using model nesting Investigation of the use of multiple atmospheric layers close to the ground surface

WP3 - Comparison with modelled and monitored data Comparison of sulphur and nitrogen concentrations and deposition generated by the Eulerian models with each other Comparison of sulphur and nitrogen concentrations and deposition generated by the Eulerian models with output from existing UK models Comparison of sulphur and nitrogen concentrations and deposition generated by the Eulerian models with field measurements

Achievements The model runs for time periods of a month on a 5km UK domain nested with a western European 45km scale domain The model outputs are comparable with observed data The effectiveness of the orographic enhancement of wet deposition is currently being studied.

Constraints Input of UK emissions data proved to be more difficult than expected The computing resource to run the model across the whole UK domain remains considerable The meteorology used comes from MM5 with ECMWF data The sub-grid scale processes (e.g. for NH 3 ) will not be improved within this project

Meteo: Hourly 3D meteorological fields from the PSU/NCAR mesoscale model MM5 BCs and ICs: Boundary and Initial concentrations from the 3D Lagrangian transport chemical model STOCHEM Emissions: CO,NO2,SO2,NH3, PM10 and PM25 from EMEP database ( and NAEI (National Emission Inventory) database ( Episode: June 1999

Concentration maps of CO,NO2,SO2 and O3 at every hour and for 6 different vertical layers Hourly trends of surface concentration in single grid cells Daily averages of surface concentration in single grid cells Scatter plots Statistical parameters Preliminary results from episode: June 1999

Concentration maps

Rochester

Daily averages

Scatter plots

Monthly averages

Future work Extension of the validation to longer periods of time (typical summer and winter periods) and more pollutants (NH3) Sensitivity analysis Emission scenarios Comparison with FRAME

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