Andrea Fraser – October 2011

Andrea Fraser, Geoff Dollard, Paul Willis,

Trevor Davies, Justin Lingard

UK Air Quality Forecasting of Particulate Matter Spring 2011

Presentation outline

Brief outline of the UK air quality forecast

Air Quality Forecast Spring 2011

PM episodes

PM Speciation during the episodes

Summary

AEA – UK Air Quality Forecast

AEA have been providing daily forecasts to protect public health and to meet specific EC Directive Requirements since 1990.

AEA’s approach is to use a team of air quality experts to compile the forecasts based on a portfolio of inputs.

Inputs Include:

• WRF-CMAQ AQ forecasting models.• Back Trajectories• Pan-European model results.• Latest UK & European monitoring data.• Weather forecasts.• Satellite imagery.• Expert judgement based on analyses of

historical air pollution episodes.

Meteorology Data produced using WRF (Weather Research and Forecasting) Model

• 50km and 10km resolution for Europe and the UK.

• 48 vertical layers.

Using GFS initial and boundary conditions

WRF-CMAQ for UK Air Quality Forecast

Emissions data

Europe – EMEP - 50km UK - NAEI - 1km Biogenic Potential Inventory - 50km

CMAQ (Community Multiscalar Air Quality) ModelVersion 4.7.1CB05 Chemistry with aerosol and aqueous extensions (AE5) Boundary conditions are from the STOCHEM global modelCMAQ uses the same resolution as WRF, with a slightly smaller grid and 25 vertical layers, with 12 layer below 800M

Extract values at monitoring stationsDaily and Monthly evaluation with monitoring data

Create ImagesAnimations and plots of daily maximum – O3 NO2 SO2 CO PM10 PM2.5

Ozone Daily max PM10 Daily Max

SO2 Daily Max

Air Quality Forecast

AQ forecasting has a few more challenges than a retrospective modelling study.

Retrospective model

• Weather is modelled using boundary conditions from models that have assimilated measurements.

• Emissions from the inventory for the year being simulated.• Boundary conditions may be taken from a variety of sources including models

that have assimilated measurement and satellite data.

Forecast model

• The weather is modelled using boundary conditions from a weather model projecting into the future.

• The emission are based on the last available year – 2009.• Generic modelled boundary conditions.

Air Quality Forecast

When making an air quality forecast you need to use your experience of model performance to decide how reliable the forecast is.

Retrospective model• Evaluate over long time periods - often months, years.• Detailed studies of specific time periods often associated with intensive

measurement campaigns. • Uses ratified measurements from automated and specialised networks and

campaigns.

Forecast model• Everyday for a over a 24 and 48 hour period.• Need to know how well the model will perform over the next few days. • Evaluated with provisional data from the Automated Urban and Rural Network

(AURN).

• We can learn about the seasonal performance from evaluation of the forecast over longer time scale.

• Use more specialised measurements for evaluation and model development

WRF-CMAQ Performance – 2010

Ozone (10km) PM10 (10km)

Ozone 2010

In 2010 Ozone had a positive bias and PM10 negative. Particularly at the Urban and Urban Background sites

PM10 (10km)

PM10 2010

“Summer-Smog” April 2011

This was the first ‘smog warning’ for two years. The unusual weather caused by a high pressure system above the UK, and pollution drifting over from Europe, combined to breach European safety limits.

High pollution episode warning: First “summer-smog” of 2011

The high pressure system persisting over the UK is forecast to bring warm and still conditions to the UK over the Easter weekend. These conditions mean it is likely that the UK will experience a high pollution episode this weekend.

Elevated levels of PM10 and ozone reaching high or moderate are expected from now until at least Sunday.

Friday 22nd April 2011

http://uk-air.defra.gov.uk/ http://www.londonair.org.uk/

Earth Observatory NASALooking more like summer than spring, the United Kingdom was wreathed in smog on April 22, 2011, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite acquired this image. According to UK Air, much of the pollution is coming from continental Europe, and some of that transport is evident in the image.

http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=50214&src=nha

March 2011 – PM10 (24hr running mean)

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Bristol St Paul's

Bury Roadside

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Cardiff Centre

Chepstow A48

Chesterfield

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London Bloomsbury

Salford Eccles

Glasgow Kerbside

Harwell

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London Harlington

Hull Freetown

London N. Kensington

Leamington Spa

Leeds Headingley Kerbside

Leeds Centre

Liverpool Speke

Middlesbrough

London Marylebone Road

Norwich Lakenfields

Nottingham Centre

Newport

Oxford St Ebbes

Plymouth Centre

Portsmouth

Port Talbot Margam

Reading New Town

Rochester Stoke

Scunthorpe Town

Sheffield Centre

Southwark A2 Old Kent Road

Southampton Centre

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Storrington Roadside

Thurrock

Warrington

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No. of stations Index 6 each hour

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No. of stations Index 4 each hour

No. AURN dlyMean above 50

ModerateIndex 4 – 65 μgm-3 Index 5 – 75 μgm-3 Index 6 – 87 μgm-3

HighIndex 7 – 97 μgm-3

March 2011

Rural sites (4) Urban Background (16)

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acr

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AU

RN

sit

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-3 g

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uiv

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Birmingham Tyburn

Birmingham Tyburn Roadside

Bristol St Paul's

Bury Roadside

Camden Kerbside

Chepstow A48

Chesterfield

Chesterfield Roadside

London Bloomsbury

Salford Eccles

Glasgow Kerbside

Harwell

Stanford-le-Hope Roadside

London Harlington

Hull Freetown

London N. Kensington

Leamington Spa

Leeds Headingley Kerbside

Liverpool Speke

Middlesbrough

London Marylebone Road

Norwich Lakenfields

Nottingham Centre

Newport

Oxford St Ebbes

Plymouth Centre

Portsmouth

Port Talbot Margam

Reading New Town

Rochester Stoke

Scunthorpe Town

Sandy Roadside

Sheffield Centre

Southampton Centre

Stoke-on-Trent Centre

Storrington Roadside

Thurrock

Warrington

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April 2011 – PM10 (24hr running mean)

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ot)

No. of stations Index 7 each hour

No. of stations Index 6 each hour

No. of stations Index 5 each hour

No. of stations Index 4 each hour

No. AURN dlyMean above 50

ModerateIndex 4 – 65 μgm-3 Index 5 – 75 μgm-3 Index 6 – 87 μgm-3

HighIndex 7 – 97 μgm-3

UK Met. Office UK overview April 2011

With areas of high pressure over or near to the UK for much of the month, there was plenty of fine, warm weather.

Temperature

The UK mean temperature was 3.7 °C above the 1971–2000 average and it was the warmest April in the series from 1910.

The daily maximum temperatures in particular were well above average, by as much as 6 °C in south-east England.

A maximum temperature of 27.8 °C was recorded at Wisley, Surrey on 23rd.

In central England, it was the warmest April for over 350 years.

Sun

It was a sunny month across all of the UK, with amounts generally close to 150% of normal, making it the sunniest April in the series from 1929.

Rainfall

Rainfall was close to or above normal over much of western Scotland, but elsewhere it was dry — exceptionally so over much of southern, central and eastern England where less than 10% of normal rainfall was recorded

http://www.metoffice.gov.uk/climate/uk/2011/april.html

WRF ForecastSurface Conditions 19th to 24th April at 12:00

23rd April

Back Trajectories

Urban Background

19th – 26th April 2011

Back Trajectories

Urban Background

Elevated PM April 2011

Evaluation of CMAQ forecast with hourly PM10 provisional data from 16 AURN Urban Background sites 12-26th April 2011

Rural and Remote Urban Background UrbanNo. of Sites 4 16 12

Normal Mean Bias (%) 8 -14 -24

Normal Mean Error (%) 44 37 41

% of pairs within a factor of 2 68 73 68

Forecast the hourly PM10 exceeding 65 μgm-3

Proportion Correct 0.96 0.91 0.97Odds Ratio Skill Score 0.98 0.90 0.64

Typical Episodes result in higher nitrate

Daily average (μg m-3)

Provisional anion measurement from NPL

Dharsheni Muhunthan (NPL) Sonya Beccaceci (NPL) David Green (Kings College London)

PM2.5 Species

Provisional AURN measurement

PM2.5 Species

Provisional AURN measurement

PM2.5 Species

Provisional AURN measurement

Summary

The UK CMAQ air quality forecast generally underestimates PM10 pollution.

During the period of moderate to high pollution in April 2011 model performance was better than in previous years.

Can we identify why model performance was better during the ‘summer smog’ of April 2011?

It was an unusual period and was challenging for the air quality forecast.

Weather – hot, dry and sunny.

Emissions:• Two four day holiday weekends with only 3

‘normal’ working days• Holidays and daytrips• Biogenic emissions

Thank you

The air quality forecast is produce on behalf of the Department for the Environment, Food and Rural Affairs and the Devolved Authorities.