Clean Air For London: ClearfLo

1. Sylvia Bohnenstengel, Stephen Belcher Clean Air For London: ClearfLo University of Reading University of York University of Leeds University of Salford CEH Edinburgh UEA University of Leicester University of Manchester Kings College London University of Birmingham University of Hertfordshire A consortium of Coordinated by National Centre for Atmospheric Science

2. Air quality is a health driver • WHO (2005) • Clean air is considered to be a basic requirement of human health and well-being • However, air pollution continues to pose a significant threat to health worldwide • Strongest health drivers: Particulate matter Ozone Nitrogen oxides Heat

3. Ambition of ClearfLo and beyond • Integrated measurements • Measure time evolving 3d met and composition for European mega city • Fully integrated met and composition • Integrated modelling + data analysis • Bridge gap between synoptic & street scales • Validate models in urban areas • Diurnal cycle of urban BL • Tools to tackle 21st century AQ issues

4. PM and health Epidemiology: High PM concentration gives health impact Increment uncertain Current trends PM emissions falling PM concentration level EEA, 2007. Air Pollution in Europe 1990–2004. EEA Report No2/2007. EuropeanEnvironment Agency, Copenhagen. Need to know: PM size, composition and processing Urban scale obs for best health metrics Estimated loss in life expectancy Courtesy Paul Monks

5. 2003 summer heat wave • In the UK, 2000 excess deaths during heat wave • 700 may have been attributable to high levels of ozone and PM10 • 20-40% of all U.K. deathsStedman, AENV, 2004 Paul Wilkinson LSHTM Measured, from Defra O3 network data and mapped by Univ. of Leicester (Lee et al, AENV, 2006) Need to know: Drivers of local temperatures Drivers of high ozone and NOx Courtesy Paul Monks UK Ozone Bubble – 2pm 6th August 2003

6. Gas phase chemistry • Further route to O3 via VOCs • Uncertainties for emission fluxes of NOX and VOC • Emissions are decreasing but concentrations stay the same • What is the biogenic component in VOC? • Contribution of secondary or recycled VOC to generation of O3 and aerosol • Testing of AQ models Photochemistry ~ minutes NO + O3  NO2 + O2 NO2 + photons  NO + O O + O2 + M  O3 + M Polluted environment ~ hours/days RH + OH  R + H2O R + O2 + M  RO2 + M NO + RO2  NO2 + RO ozone formation NOx acts as catalyst for O3 production from VOCs. Paradoxically, emission controls in vehicles lead to increases of O3 in urban areas.

7. Gas phase chemistry Photochemistry in urban areas generally understood. The concentration of NOx and other photochemical accelerants can lead to excess urban chemistry: HONO + photons  OH + NO (HONO increased with modern engines)  O3 formed from secondary sources. • Need to understand OH budget (lifetime and concentration) to understand daytime photochemistry • Test process understanding and source understanding for models and emission inventories

8. Particulate matter • estimate of the amount of secondary aerosol formed with the city • large proportion of PM in London may be generated as secondary aerosols from biogenic gas phase precursors • major impact on the ability of anthropogenic regulation alone to control future PM in UK cities • Clearflo can provide the experimental basis to test this hypothesis of a major London biogenic source

9. Meteorology: Measurements and models • Seasonal variation of urban boundary layer • Seasonal variation • Model evaluation • Analysis of night-time decoupling events • Processes determining magnitude of UHI • Processes determining timing of UHI • Quantification of sea breezes across London • Model runs for May case study

10. Strategy for ClearfLo: Atmospheric Science for Health Impacts of Urban Air Quality Health Drivers PM Ozone and NOx Heat waves • Atmospheric Science Questions • Urban meteorology • Heat balance • BL depth • Evolution of PM • Size + composition • Processing • Evolution of gas phase • Emission + oxidation • Processing • Measurement strategy • Establish infrastructure • Long-term measurements • Seasonal variations • IOPs • Process studies Process studies • Predictive tools: • Strengths & Weaknesses

11. Measurement sites Core measurements Ozone, NOx, CO, NOy Particle size spectrum .0025–10μm Particle mass, PM10, PM2.5 Particle composition samples Boundary-layer structure and energy fluxes Elevated BT Tower (180m) KCL Roof (35 m) Urban increment Rural Chilbolton Detling Harwell Urban background North Kensington Kerbside Marylebone Road Rural background Detling Add value to existing sites

12. Intensive Observation Periods • Winter and summer campaigns • 9th Jan – 12th Feb 2012 + 20th Jul – 23rd Aug 2012 (Olympics) • Comprehensive instrumentation • Vertical structure of urban BL • Oxidation budget of urban BL • Composition and properties of PM • Location: Sion Manning school, North Kensington • Call for proposals in January • Allow external participation

14. Judith

15. Weather Conditions In London on the 14th-17th January 2012

16. What sort of weather was London seeing? • UK was under the influence of firmly-established high pressure, so the well-subsided airmass above London was eliminating most cloud. So the urban surface could radiate freely. • Wind direction had changed from more southerly flow to northeasterly, allowing temperatures to be cooler still. • Winds were relatively calm and the conditions settled, so urban pollutants were not being rapidly advected . • Temperatures were dropping below 0°C at night and freezing mist and fog patches took some time to clear in the mornings • Stationary weather and low winds meant that the pollution in London would have been mainly locally-driven, and clear skies will lead to a strong Urban Heat Island (UHI) effect.

17. London acting as a “mixing layer dome” The increased surface roughness and the UHI effect contribute to a deeper circulating mixing layer over urban areas. In clear, high pressure conditions without strong winds pollution can accumulate, leading to high concentrations.

18. ‘“Moderate” air pollution incident notification from King’s College London Environmental Research Group • Issued: 14:30 Monday 16th January 2012Summary“Settled, cold weather on Saturday 14th January led to a buildup of local traffic pollution. Widespread ‘moderate’ nitrogen dioxide and PM10 and PM2.5 particulate was measured close to busy roads throughout London in both central and suburban areas. The greatest PM10 concentrations were measured alongside the North Circular in Brent and the greatest nitrogen dioxide was measured in Knightsbridge.‘Moderate’ PM10 particles were also measured in residential west London at the National Physical Laboratory in Teddington.Further west, ‘moderate’ PM10 and PM2.5 particles were measured in Reading. ‘Moderate’ PM10 was also measured in Sussex alongside the A259 east of Bexhill-on-Sea and alongside the A2011 in Crawley. North of London, ‘moderate’ PM10 was measured alongside the A1 in Bedfordshire.Outside the south east, ‘moderate’ PM10 and PM2.5 particles were measured in many cities in the eastern half of England. “

20. Maximum and Minimum Temperatures

21. Radiation & Wind Direction

22. Lidar Results

28. UKV

29. 12 13 14 15 16 • 17 18 19 20 21 22 • 23 24 25 26 27 28 • 29 30 31 UHI (London – Detling) UHI (London – Harwell) January 2012 UKV Model output

30. Surface energy balance - Forcing

31. Spatial evolution of potential temperature profile 03 06 12 UTC Previous’ days daytime mixed layer Surface layer starts to warm Stable nocturnal Surface layer 15 18 21 UTC Well mixed daytime layer – urban is deeper than rural Urban less stable then rural profiles Unstable urban surface layer Well mixed urban, but stable rural surface layer

32. Temporal evolution of potential temperature profile Harwell BT Tower Detling More mixing during evening and night 18 UTC and later Wind direction

33. Next steps for this case study • Comparison with lidar and BT tower measurements • In which AQ variables do we find the urban increment observed in the MET? • Analyse a large-scale driven case to contrast results.

34. ClearfLo Jan/Feb 2012 IOP Air Quality Modelling and Measurements

35. Some chemistry produced From cars ~ minutes Used up molecule NO released by cars; O3 depleted, so none near cars These are fast reactions ~ minutes

36. Polluted air ~ hours From cars produced These are slow reactions ~ hours NO/NO2 ratio affected by these processes Ozone formation catalysed by NOx

37. Jan 16 case study – AQUM simulations

40. North Kensington measured data

41. Fire on 31/01/12

42. Aethalometer and MAAP