Models-3 Performance for UK Air Quality

1. Models-3 Performance for annual deposition and air quality in the UK Ian Rodgers

2. Why Models3? • Why did we select this model? • ‘future proof’ methodology via modular science • range of spatial scales (to enable single station to transboundary calculations in a single framework) via grid nesting • range of time scales (to enable simulation of air quality episodes through to annual depositions) • air quality, acidification, eutrophication, ozone, particulates in a single model simulation – consistency • Models-3/CMAQ emerged as best match to requirements from a review of available methods

3. Models-3 key capabilities • Eulerian model • Dynamic model of atmospheric transport and processes • Atmosphere resolved vertically • ‘1 atmosphere’ model • Nested grid capability • Plume rise and PinG model • RADM/CB4 • Particulates via 3 log-normal modes • Wet deposition via aqueous extension to chemical scheme, and coupling to cloud processes • Dry deposition via resistance analogy

4. Approach to development of Models-3 • Build Models-3/CMAQ domain to include a large enough region of Europe to provide good boundary fluxes for U.K. • Use nested grid capability to provide 4km grid resolution for test region in Midlands • Build key inputs • Emissions: various public sources, incl EMEP, NAEI (UK) • Meteorology: UK Met Office NWP output • ‘unsolder’ hard-wired features! • Test performance of ‘vanilla’ model on annual run for 108 -> 12 km grids

5. Current studies • A number of studies are currently being performed: • Validation of Models-3 wet deposition modelling • Full-year simulation of air quality and deposition for the U.K. (joint JEP/Environment Agency study) • Validation of Models-3 particulate modelling • Testing of Models-3 plume rise and plume in grid methodologies • Development & testing of an aggregation scheme

6. Development of Models 3 - Europe-scale model domain

7. Development of Models 3 - UK modelling domains

8. Major point source emissions included in model

9. Location of monitoring sites used

10. Annual comparison: precipitation

11. Annual comparison: wet deposition of S

12. Annual comparison: wet deposition of oxidised N

13. Annual comparison: wet deposition of reduced N

14. Model – measurement comparison for wet depn.

15. Model – measurement comparison for AQ

16. Summary of conclusions from study • At 12km resolution, Models-3 gives reasonable simulations of the wet and dry deposition of sulphate, nitrate, and reduced nitrogen species. • It also gives reasonable simulations of the atmospheric concentrations of SO2, NO2, NH3, and particulate. • Agreement with measurements for wet deposition improves with increasing averaging time and the model gives good results for an annual simulation, the period of most interest for acid deposition. • Models-3 performance for wet deposition compares favourably with the EMEP Lagrangian model. • Rainfall obtained from Numerical Weather Prediction (NWP) models is inherently limited by the fact that it is a sub-gridscale process represented within the meteorological model. • Total deposition maps are in fair agreement with interpolated measurements. • Models-3 is a suitable model for use as a high-resolution long-range transport model for the UK and Europe.

17. The next steps • Data mining of Gbytes of data generated to date • Detailed testing of impact of choice of science representation for JEP company priority issues • Use of Models-3 for effects assessment and case making • Comparison of performance with other models • Would welcome interaction with other users / potential users • Training and workshop sessions

19. Science content overview • 3D Eulerian method • Nested grid capability • our studies have used 108, 36, 12 and 4 km grids • Terrain-following vertical coordinate • Modular design to allow ‘plug & play’ science representation • ‘One atmosphere’ model • Source code access

20. Models3 process flow

21. Modular approach to science

22. Science content - meteorology • Meteorology • driven by 3-D Met fields from external met. model • Models3 is set up to use output from MM5 mesoscale model • Innogy have written utility to take Met Office Global and Mesoscale model output and write into MM5 format • met data preprocessor used to derive required boundary layer and surface parameters

23. Science content - mixing • Vertical diffusion via eddy diffusion approach • Horizontal diffusion either constant diffusivity or simple function of wind speed • Plume in grid model for plume rise, chemistry and dispersion • intended for largest point sources • Briggs-like final plume rise formula • plume advected through grid until reaches critical condition • plume vertical & horizontal spread • full CMAQ chemical evolution • dry deposition, and effect of surface emissions into plume

24. Science content - chemistry • Gas, liquid and solid chemistry treated separately • Gas-phase chemistry via either RADM2 or CB4 • linked to aerosol and aqueous chemistry modules

25. Science content - deposition • Dry deposition via resistance analogy from bl vertical profiles and land cover type • canopy resistance broken down to sub-canopy processes • Cloud processes and wet deposition • sub-grid and resolved cloud • in-cloud mixing, scavenging, aq. chemistry and wet deposition • accumulation & coarse mode particulate incorporated into cloud & rain water

26. Science content - aerosols • Aerosol represented as 3 lognormal modes • PM2.5 - Aitken and accumulation modes • PM2.5 - PM10 • each mode describes particle number, surface area and mass concentrations • Primary & secondary particulates included • 2ndary: sulphate, nitrate, ammonium, water, organic & elemental C • Primary: sea salt, wind-blown dust, unspecified