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Ian Longley Street canyon aerosol pollutant transport measurements in Manchester I.D. Longley, M.W. Gallagher, J.R. Dorsey, M. Flynn, K. Bower, I. Barlow.

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Presentation on theme: "Ian Longley Street canyon aerosol pollutant transport measurements in Manchester I.D. Longley, M.W. Gallagher, J.R. Dorsey, M. Flynn, K. Bower, I. Barlow."— Presentation transcript:

1 Ian Longley Street canyon aerosol pollutant transport measurements in Manchester I.D. Longley, M.W. Gallagher, J.R. Dorsey, M. Flynn, K. Bower, I. Barlow J.R. Allan, M.R. Alfarra, H. Coe

2 Ian Longley Aerosol in Urban Street Canyons Fine aerosol, linked to adverse health effects (COMEAP, 2001, EPAQS,2000, Colville et al, 2001). Fine aerosol from vehicle emissions. Street canyons act as major emission sites. Large numbers of people exposed. Canyons re-circulate and trap pollutants. Canyon emissions transported across and beyond city – affecting chemical and radiative atmospheric properties and the biosphere. Need to understand transport within, and emission from, urban street canyons.

3 Ian Longley SCAR – Street Canyon Aerosol Research Regulatory dispersion models are based upon a simple transport mechanism – PM 10 only. Numerical modelling – simple canyons. Field studies are rare. SCAR to apply eddy correlation techniques. Aim: Parameterised size- segregated aerosol emission rates.

4 Ian Longley Experimental site – Princess Street, Manchester

5 Ian Longley SCAR measurements SMPS (TSI nano DMA) OPC (PMS ASASP-X) FSSP 20 Hz sonic anemometers 18m mast Platform lift for profiling Mobile turbulence system 4 campaigns in 2001: (3 x 1 week, 1 x 2 weeks)

6 Ian Longley Mean ultrafine aerosol spectra Left: SMPS spectrum from UMIST Land Rover Discovery TDi Left: average SMPS spectrum from SCAR, 2m height

7 Ian Longley Aerosol Chemistry (from Aerosol Mass Spectrometer, J.R. Allen, M.R. Alfarra, H.Coe) Mode in the mass spectra at around nm consisting of aliphatic organic chemicals. Organic activity within the Manchester sampling periods correlates well with NO x activity.

8 Ian Longley Temporal variation in fine aerosol spectra (4.6nm

9 Ian Longley Mean air flow: Channelling

10 Ian Longley Mean air flow: Vertical flow

11 Ian Longley Mean air flow: Vertical flow

12 Ian Longley Mean air flow: Up-canyon

13 Ian Longley Mean air flow: NE perpendicular

14 Ian Longley Mean air flow: SW perpendicular

15 Ian Longley Influence of wind speed and direction on fine aerosol number concentrations – 1. PARALLEL FLOW

16 Ian Longley Influence of wind speed and direction on fine aerosol number concentrations – 2. NE PERPENDICULAR Canyon vortex blows emissions away from instruments

17 Ian Longley Influence of wind speed and direction on fine aerosol number concentrations – 3. SW PERPENDICULAR Canyon vortex blows emissions towards instruments Flow at pavement level disconnected from roof-top wind

18 Ian Longley Vertical concentration gradients

19 Ian Longley Vertical concentration gradients

20 Ian Longley Accumulation mode (100nm

21 Ian Longley Horizontal fluxes

22 Ian Longley Coarse particle fluxes SASUA All Experiments Aerosol Eddy Flux Measurements d p >1.9  m Mode- CEH instrument Wind driven re-suspension

23 Ian Longley Vertical turbulence

24 Ian Longley Parameterisation for  w Traffic-induced turbulence

25 Ian Longley Parameterisation for  w = 0.16 at a height of 3.5m  wt = T 1/2 T = traffic flow rate (hr -1 )

26 Ian Longley Turbulent variances:  w /U profiles

27 Ian Longley Turbulent variances:  u /U profiles

28 Ian Longley Turbulent variances:  v /U profiles

29 Ian Longley Spatial variation in  w /U: 1. Sheltered zone Above: U/U roof Below:  w /U Plan views of canyon

30 Ian Longley Spatial variation in  w /U: 2. Convergence Above: U Below:  w /U

31 Ian Longley Conclusions  The flux of accumulation mode aerosol (100nm

32 Ian Longley Forthcoming analysis More street-level accumulation mode flux data Profiles of coarse aerosol concentrations Improved parameterisation for wind-driven re- suspension Spectral & quadrant analysis SCAR-5: suburban street canyon Improved parameterisation for turbulence, including traffic-layer turbulence


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