1. DAPPLE Science Meeting Tuesday 30 th November 2004, Imperial College London. Air Flow – Fieldwork: Sam Arnold (1&2), Adrian Dobre (2), Rob Smalley (3), Janet Barlow (2), Stephen Belcher (2), Doug Boddy (3), Ian Harman (2), Jethro Redmore (3) & Alison Tomlin (3). (1) Imperial College London, (2) University of Reading, (3) ERRI, University of Leeds. Supported by data from: The Met Office & QinetiQ

2. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. Objectives: To investigate: the relationship between street level (constrained) and rooftop winds; how the horizontal advection compares with the vertical mixing in urban envs; the turbulent fluxes and mean flows across the intersection in the centre of the road; vertical turbulent fluxes; more comprehensively the characteristics of the above-roof winds; ground level flows with mobile sonics in 2004 only – to provide support for exposure and tracer tracer releases. Key: Both, 2003 only, 2004 only.

3. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. DAPPLE 2003: Existing Analysis Papers: Arnold et al (2004) – Introduction to the DAPPLE project – STOTEN, 332, 139-153; Dobre et al (2004) - Flow field measurements in the proximity of an urban intersection in London, UK– to be submitted to Atmospheric Environment ASAP; Main Conference Presentations: 5-th Conference on Urban Env., Vancouver - Aug 2004 Clean Air Congress – Aug 2004 UWERN – Dec 2004

4. Roof-top conditions DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. Pdf of the roof-top wind direction Sector mean wind speeds θ Marylebone Rd

5. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. Horizontal flow patterns NW roof-top windsSW roof-top winds Switching Channeling Apparent mirroring  Pdf of wind directions based analysis

6. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. Decomposition model Helical effect Axial advection Recirculation U rt V rt u v θ rt θ

7. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. Decomposition Model Roof-top wind component parallel to the street, U rt In-street axial wind component, u V rt sqrt(v 2 +w 2 ) R 2 =0.78 R 2 =0.39

8. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. Hall Farm measurements Aim: To investigate the mechanisms responsible for venting urban street canyons To measure detrainment and subsequent re- entrainment PMCPPMCH SF 6 3.2m 1m 1. 2.3.

9. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. DAPPLE 2004: Preliminary Analysis Data check: total of 53 days of roof-top measurements, 43 days of BT tower, 22 days of street level data. Initial data post-processing: Time stamped files with raw data and 10minute averages for the whole campaign; also 1 minute averages for the 3 “special days”: DUST release and 2 TRACER releases

10. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. Synoptic conditions wind direction wind speed max 2.5m/s at roof-top! BT tower: 180 m θ Marylebone Rd 10 min averages

11. DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. DAPPLE 2: In-street winds

12. DAPPLE 2: Site 1 180º N 250 º 90º 0º0º 270 º 180º DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London.

13. Site 1: variation with height -60 º -10º 225 º lower: 4.1 mupper: 8.3 m 90º 0º0º 270 º 180º DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London.

14. DAPPLE 2: Site 2 210º 160 º lower: 4.4 mupper: 8.1 m 90º 0º0º 270 º 180º DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London.

15. DAPPLE 2: Site 3 225º 90º 0º0º 270 º 180º DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London.

16. DAPPLE 2: Site 4 DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London. significant “apparent reflection”

17. Sites 1 – 4: analysis An effective above-roof reference needs to be selected Variation of mean flow and turbulence with height (4.0 < H (m) < 8.5): - significant within the intersection (site 1) -minimal within the canyon and on the intersection boundary (site 2) Turbulence intensity relatively high (~250%) Turbulence measured is more isotropic compared with data from the building edge. (To present at UWERN December 2004, with York data) Application to pollutant dispersion: The influence of air flow regimes on the concentration of a traffic related pollutant in the vicinity of a complex urban intersection (submitted as a presentation at UAQ5, March 2005) DAPPLE Science Meeting Tuesday 30th November 2004, Imperial College London.

18. Unifying Themes 1 Helical mean flow in streets 1.Sensitivity to above roof wind direction 2.DAPPLE II: 1.Tool for understanding tracer release? 2 Intermittency 1.Definition: Intermittent excursions from mean 2.Flow switching at intersections as mechanism 3.DAPPLE II: 1.Vertical coherence of switching 3 Neighbourhood preconditioning 1.Upstream and downstream neighbourhood flow 2.DAPPLE II: 1.Use different synoptic wind directions 2.Which above roof wind for reference?