aerosol measurements in london using the opal weather station network: preliminary results from the...
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![Page 1: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/1.jpg)
Aerosol Measurements in London using the OPAL Weather Station Network:
Preliminary Results from the EM25 Campaign
Claire McConnell
Ralf Toumi (Imperial College)EM25:
Jim Haywood (Met Office), Patrick Chazette (LSCE), Will Morgan (Manchester)
![Page 2: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/2.jpg)
Motivation
• Measurement of column aerosol load– Total column load important for radiative effect (SW
and LW), interaction with clouds, long range transport• Spatial distribution of aerosol across London– Transport of London aerosol plume, input from
outside London• Development of a cheap, automatic, freely
available, educational network of measurements across London
![Page 3: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/3.jpg)
OPAL Weather Station Network
• Currently 38 Davis weather stations in London – a few more awaiting installation
• Measure pressure, T, RH, precipitation, wind speed & direction, solar radiation, UV index
• Data recorded every minute• Most located in schools• Locations not always optimal,
data uncalibrated (so far)
![Page 4: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/4.jpg)
LGfL Weather Website• Data publicly available at http://
weather.lgfl.org.uk• Publicly available for previous month• Complete (secure) archive
– All data– Requires registration– Allows csv downloads
![Page 5: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/5.jpg)
Using Solar Radiation to Infer Aerosol Loading
• Dense network of solar radiation measurements (low quality?) – probably only existing urban network
• Simple method to capitalise on high density measurements:– Use change in solar radiation flux over time to infer
amount of aerosol– → spatial distribution of aerosol– Sky must be clear!
• Data available for every minute, presently using 30 minute averages
![Page 6: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/6.jpg)
Technique: Langley Extrapolations• Plot ln(I) against air mass
(1/cos(θ) )• Calculate gradient of ln(I)
and air mass• Magnitude of gradient
indicates amount of aerosol present
Time
Solar Radiation (I)
Clear sky
AOD at 550nm = 1.0
![Page 7: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/7.jpg)
Test Case: 23rd June 2009
![Page 8: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/8.jpg)
Focus on Clear Times1300Z 1400Z
1500Z 1600Z
![Page 9: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/9.jpg)
Langley Extrapolation Results
Wind E to NE
![Page 10: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/10.jpg)
Comparison with Other DataOPAL solar radiation PM10 PM2.5
Met Office Aerosol ForecastMODIS 550nm AOD 1050Z MODIS 550nm AOD 1240Z
![Page 11: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/11.jpg)
EM25 Campaign
• 16th – 26th June 2009• BAe145 aircraft
– circuits around London and the UK coast– Vertical profiles at Farnborough, Northolt,
Biggin Hill, Southend– Aerosol size distribution, scattering,
absorption, composition– Chemistry (CO, Ozone, NOx...)– Met variables– Lidar (failed)
• French Lidar van– circuits around M25, cross-sections from
Reading to Imperial– Vertical profile of back scatter
![Page 12: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/12.jpg)
Daytime, 23 June (10:10-12:50 GMT)Flight 4 (1/2)
Trip between Reading and Dover during the comeback to France.
Cloud free condition.
M25, Paris, 24/09/2009
Courtesy of P. Chazette, LSCE
![Page 13: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/13.jpg)
Daytime, 23 June (10:10-12:50 GMT)Flight 4 (2/2)
Other area subjectsto pollution!
M25, Paris, 23/09/2009
Courtesy of P. Chazette, LSCE
![Page 14: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/14.jpg)
Next Steps...
• Look-up table to convert from measured Langley gradient to AOD
• Switch to high resolution OPAL data (every minute)• Sensitivity tests• Calibration/instrument comparisons• Other clear days?• Longwave radiative effect of London aerosol
– IR camera for EM25 campaign• Weather station data
– Urban heat island?
![Page 16: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/16.jpg)
PM2.5 in 2 hour intervalsNote change in pattern throughout day from E-W split to NE-S split
![Page 17: Aerosol Measurements in London using the OPAL Weather Station Network: Preliminary Results from the EM25 Campaign Claire McConnell Ralf Toumi (Imperial](https://reader038.vdocuments.us/reader038/viewer/2022110207/56649d2e5503460f94a053e1/html5/thumbnails/17.jpg)
Longwave Aerosol Effect
AOD=1.0AOD=0.0
Theoretical calculations with SBDART, 8-12um.