Clean Air For London: ClearfLoClean Air For London: ClearfLo

A consortium of

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

Coordinated by

National Centre for Atmospheric Science

Sylvia Bohnenstengel, Stephen BelcherSylvia Bohnenstengel, Stephen Belcher

Air quality is a health driverAir 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

Ambition of ClearfLo and beyondAmbition 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

PM and health

• Epidemiology:– High PM concentration

gives health impact– Increment uncertain

• Current trends– PM emissions falling– PM concentration level

Need to know:

PM size, composition and processing

Urban scale obs for best health metrics

Estimated loss in life expectancy

EEA, 2007. Air Pollution in Europe 1990–2004. EEA Report No2/2007. EuropeanEnvironment Agency, Copenhagen.

Courtesy Paul Monks

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

UK Ozone Bubble – 2pm 6UK Ozone Bubble – 2pm 6thth August 2003 August 2003

Paul Wilkinson LSHTM

Need to know:

Drivers of local temperatures

Drivers of high ozone and NOx

Measured, from Defra O3 network data and mapped by Univ. of Leicester (Lee et al, AENV, 2006)

Courtesy Paul Monks

Gas phase chemistryPhotochemistry ~ 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.

• 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

Gas phase chemistryPhotochemistry 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 photochemistryTest process understanding and source understanding for models and emission inventories

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

Meteorology: Measurements and models

1. Seasonal variation of urban boundary layero Seasonal variationo Model evaluation

2. Analysis of night-time decoupling eventso Processes determining magnitude of UHIo Processes determining timing of UHI

3. Quantification of sea breezes across Londono Model runs for May case study

Atmospheric Science Questions• Urban meteorology

– Heat balance– BL depth

• Evolution of PM– Size + composition– Processing

• Evolution of gas phase– Emission + oxidation– Processing

Strategy for ClearfLo: Atmospheric Science for Health Impacts of Urban Air Quality

Health Drivers

• PM

• Ozone and NOx

• Heat waves

Measurement strategy• Establish infrastructure• Long-term measurements

– Seasonal variations• IOPs

– Process studies

Process studies

Predictive tools:

• Strengths & Weaknesses

Core measurementsOzone, NOx, CO, NOy

Particle size spectrum .0025–10μm

Particle mass, PM10, PM2.5

Particle composition samples

Boundary-layer structure and energy fluxes

Rural

Chilbolton

Detling

Harwell

Urban background

North Kensington

Kerbside

Marylebone Road

Elevated

BT Tower (180m)

KCL Roof (35 m)

Measurement sites

Add value to existing sites

Urban increment

Rural background Detling

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

Judith

Weather Conditions

In London on the 14th-17th January 2012

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.

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.

‘“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. “

Maximum and Minimum Temperatures

Radiation & Wind Direction

Lidar Results

UKV

UHI (London – Harwell)

UHI (London – Detling)

11 12 13 14 15 16

17 18 19 20 21 22

23 24 25 26 27 28

29 30 31

January 2012 UKV Model output

Surface energy balance - Forcing

15 18 21 UTC

03 06 12 UTC

Previous’ days daytime mixed layer

Stable nocturnal Surface layer

Well mixed daytime layer – urban is deeper than rural

Unstable urban surface layer

Well mixed urban, but stable rural surface layer

Urban less stable then rural profiles

Spatial evolution of potential temperature profile

Surface layer starts to warm

Temporal evolution of potential temperature profile

Harwell BT Tower Detling

More mixing during evening and night 18 UTC and later

Wind direction

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.

ClearfLo Jan/Feb 2012 IOP

Air Quality Modelling and Measurements

Some chemistry

NO released by cars; O3 depleted, so none near cars

These are fast reactions ~ minutes

~ minutes

From cars

Used up

produced

molecule

Polluted air

These are slow reactions ~ hours

NO/NO2 ratio affected by these processes

Ozone formation catalysed by NOx

~ hours

From carsproduced

Jan 16 case study – AQUM simulations

North Kensington measured data

Fire on 31/01/12

Aethalometer and MAAP