The impact of boundary layer dynamics on mixing of pollutants Janet F.Barlow 1 , Tyrone Dunbar 1 , Eiko Nemitz 2 , Curtis Wood 1 , Martin Gallagher 3 , Fay Davies 4 and Roy Harrison 5 1 University of Reading 2 Centre for Ecology and Hydrology 3 University of Manchester 4 University of Salford 5 University of Birmingham Funded by The BOC Foundation
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The impact of boundary layer dynamics on mixing of pollutants
The impact of boundary layer dynamics on mixing of pollutants. Janet F.Barlow 1 , Tyrone Dunbar 1 , Eiko Nemitz 2 , Curtis Wood 1 , Martin Gallagher 3 , Fay Davies 4 and Roy Harrison 5 1 University of Reading 2 Centre for Ecology and Hydrology 3 University of Manchester - PowerPoint PPT Presentation
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The impact of boundary layer dynamics on mixing of pollutants
Janet F.Barlow1, Tyrone Dunbar1, Eiko Nemitz2, Curtis Wood1, Martin Gallagher3, Fay Davies4 and Roy Harrison5
1University of Reading2Centre for Ecology and Hydrology
3University of Manchester4University of Salford
5 University of Birmingham
Funded by The BOC Foundation
Urban Boundary Layer dynamics: effect on aerosol distribution
City scale:
(from Oke, 1987)
Urban Boundary Layer dynamics: effect on aerosol distribution
Neighbourhood scale:
• heat and moisture sources / drag sinks are patchy• aerosol / precursor gas sources are patchy too!• vertical structure of turbulence and aerosols varies spatially and diurnally
Simultaneous measurements required to attribute variability in pollutant concentrations to both dynamical and chemical processes
REPARTEE campaign 2007
Regents Park
Lidar Site BT TowerDAPPLE roof site
Aim:Intensive observations of aerosols, trace gases and boundary layer dynamics to quantify variability in urban pollutants due to both chemical and meteorological processes.
Special Issue in Atmospheric Chemistry and Physics!
• 24th Oct to 14th Nov 2007 • vertical stare• 30 m resolution gates• integration every 4 sec
• backscatter• along beam Doppler velocity (vertical component)
Doppler lidar measurements
• R3 sonic anemometers (Gill)• 15th Oct to 15th Nov • 20Hz sampling frequency• height z = 190 m (BT), 17 m (roof)• wind velocity, sonic temperature, fluxes
• Big changes in: mixing height, strength of turbulence, vertical structure of turbulence
What is the impact on upward mixing of pollutants?
Estimated time to diffuse from surface up to BT Tower
Tim
e (
secon
ds)
Conclusions• Doppler lidar gives reliable measurements of turbulent structure of urban boundary layer
• Lidar measurements indicate well-mixed profiles by day, separate layers of aerosol and turbulence at night of depth ~100-500m
Occasionally during night-time ground-level and BT Tower measurements can diverge, i.e. the flow is decoupled from the surface• Mixing timescales depend on boundary layer turbulenceHow far will pollutants be transported vertically (horizontally)?