Ozone Modelling in the UK

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Ozone Modelling in the UK

• Garry Hayman
• Joint Meeting of the TFMM and TFIAM
• IIASA, 16th-17th November 2006

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Content and Acknowledgements

• Content
• The Ozone Source-receptor Model
• Model Performance
• The Urban Ozone Decrement
• Summary
• Acknowledgements
• John Abbott (netcen)
• Dick Derwent
• Met Office (for met data)
• Defra and the Devolved Administrations

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Ozone Source-receptor Model (OSRM)

• UK ozone policy tool
• Builds on earlier ozone models
• Calculates air mass trajectories from global met.
  datasets (1995-2005 available)
• Uses emission inventories taken from NAEI and
  EMEP
• Chemical mechanisms based on STOCHEM-ELMO or CRI
• Full diurnal calculation to represent depletion
  of ozone in the shallow night-time boundary layer
• Option to define major urban areas at higher
  spatial resolution

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Observed vs. Modelled O3 Concentrations
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OSRM Postprocessor

• Derives a range of outputs from
  calculated/observed hourly concentrations O3
  (29), NO (1) and NO2 (3) metrics, O3 frequency
  distributions and histograms
• Surface Conversion Algorithm developed to address
  overprediction of O3 and underprediction of NOx
  in urban areas

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OSRM Postprocessor Surface Conversion

• Assume stability constant (ku/?) is constant
  with height and transform to resistance-based
  co-ordinate system
• Coupled differential equations solved iteratively
  with assumed upper and lower boundary conditions

• Solve coupled differential equations for O3, NO
  and NO2

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Effect of Surface Conversion Harwell - 2001
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Effect of Surface Conversion Bloomsbury - 2002
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OSRM Performance for Selected Ozone Metrics
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OSRM as Supplementary Assessment Method
Empirical OSRM AOT40 Crops (5-Year Average
2000-2004)
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Evaluation of OSRM as Supplementary Assessment
Technique
Empirical OSRM AOT40 Crops (5-Year Average
2000-2004)
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Recent Policy Application Review of the UK Air
Quality Strategy

• OSRM Model Runs
• UK 10 km x 10 km Receptor Grid
• Current Years, 2010, 2015, 2020
• NAEI emission inventories and projections
  developed for Review
• 2003 meteorology
• Allow for changing atmospheric composition
• Sensitivity Runs
• Meteorology (2000 and 2002)
• Atmospheric Composition
• Emissions
• OSRM Output
• Surface-conversion Module activated
• Focus on 1 NO2 and 7 O3 metrics
• Presented as Population- or Area-weighted Means

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Review of the UK Air Quality Strategy Base Case
Runs
(Relative to 2003 1)
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Current vs. Future Atmospheric Composition
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Review of the UK Air Quality Strategy Key Results

• The base case runs show a progressive worsening
  of ozone air quality for all metrics from 2003 to
  2010 and beyond
• Smaller local NOx titration in urban areas as NOx
  emissions are reduced
• Increased photochemical production as NOx
  inhibition is reduced
• Increasing O3 background arising from climate
  change
• Meteorological effects and year-to-year
  variability in meteorology can have a larger
  effect on ozone air quality than the emission
  control measures considered.

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Urban Ozone Decrement

• Ozone concentrations modelled at 41 UK monitoring
  sites for the years 1999-2005
• 20 rural sites, 10 London and 11 other urban
  sites
• Metrics calculated with and without surface
  conversion
• Without Surface Conversion Effective Regional
  O3 Concentration
• With Surface Conversion Actual O3
  Concentration
• Calculate O3 decrement as
• ?O3 metric O3 metric (with SC) - O3 metric
  (no SC)
• Is there a correlation between the O3 decrement
  and the grid square NOx emission?

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EMEP NOx Emission
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Urban Decrement No Cutoff
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Urban Decrement 35 ppb Cutoff
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Urban Decrement AOT40 Crops
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Correlation using Emission Inventories at Higher
Spatial Resolution
1 km x 1 km 10 km x 10 km
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Urban Decrement No Cutoff
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Urban Decrement 35ppb Cutoff
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Urban Decrement AOT40 Crops
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Approach for Integrated Assessment Modelling

• Emissions
• High resolution NOx emission inventories
• Meteorology
• Aerodynamic resistance
• Boundary Layer Height
• Temperature
• Photostationary State Chemistry
• Photolysis Rate of NO2
• Rate constant for NO O3
• Ozone Deposition
• Land Cover
• Stomatal resistances for different surface
  coverages
• Non-stomatal resistances

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European High-Resolution Emission Inventories
Dataset Total NOx Emissions Source Convention
on Long Range Transboundary Air Pollution
(CLRTAP) Attribute/Description NOx Emission in
Tonnes per square kilometer Scale/Geography Raste
r, 1 km2 pixel Time period 2001 Geographic
extent All countries (except Sweden and Norway)
Courtesy of EU APMoSPHERE Project
(http//www.apmosphere.org/)
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Land Cover - PELCOM

• Features
• Land Use Classification
• Similar to CORINE LC types
• Resolution 1.1 x 1.1 km²
• One system for all of Europe

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Summary

• Ozone Source-Receptor Model, its performance and
  applications described
• OSRM gives a reasonable description of ozone
  across the UK over a number of recent years
• Ozone decrements investigated. Stronger
  correlation with higher resolution NOx emissions
• Potential approach outlined for application in
  integrated assessment models