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Meteorological Institute Klima Campus University of Hamburg. 17.08.11. High resolution modelling for London, UK using an urban surface exchange parameterisation for METRAS. David Grawe 1,2 , Heather Thompson 2 , Jennifer Salmond 3 , Xiao-Ming Cai 2 , Heinke Schl ü nzen 1

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17.08.11

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  1. Meteorological Institute Klima Campus University of Hamburg 17.08.11

  2. High resolution modelling for London, UK using an urban surface exchange parameterisation for METRAS David Grawe1,2, Heather Thompson2, Jennifer Salmond3,Xiao-Ming Cai2, Heinke Schlünzen1 1 Meteorological Institute, Klima Campus, University of Hamburg, Germany 2 School of Geography, Earth and Environmental Sciences, University of Birmingham, UK 3 School of Environment, University of Auckland, New Zealand

  3. Introduction Motivation • Direct influence of tall buildings and sealed surface onmeteorological variables • Indirect impact on dispersion and chemical reactions • Changes in land use due to urbanisation Aim • Evaluation of the implementation • Description of regional influence of urban effect

  4. Urban Areas localshading sealedsurfaces emissions wind,turbulence radiativetrapping

  5. METRAS • 3d mesoscale numerical model • prognostic, non-hydrostatic • Part of M-SYS:METRAS / MECTM / MITRAS / MICTMused as meteorological preprocessor for chemistry model • Previously: 10 land use classes, incl 1 urban(has been extended since this study) • Sub-grid land use with flux averaging

  6. BEP • BEP: Building Energy Parametrisation • Martilli et al (2002) • Multi-layer1d-model • Implementedinto severalother models METRAS- and BEP-grid

  7. BEP Dynamical effect Influence of horizontal and vertical surfaces on momentum, TKE, turbulent length scales Thermodynamic effect Turbulent heat flux above horizontal surfaces Surface enegy budget with radiative trapping and shading Heat diffusion equation solved for all surfaces

  8. BEP Input Data • Building height distriution asprobability distribution(several classes) • Direction of street canyons • Street and building width • Core building temperature z [m] Roof height of buildings Fraction [%]

  9. Application to London Fraction ofurban land use Orography [m] [%] (from CEH Edinburgh) (from USGS)

  10. Set-up for London domain Domain dimensions Size 70 x 70 km² (100 x 100 km²) Resolution 1 x 1 km2 Land use Realistic land use with two urban classes Meteorological conditions Driven with radiosonde data every 6 hours

  11. Selected situations 30-31 July 1999 Temperatures above average No/few clouds Low wind speed 6-7 August 1998 Part of a longer period with average UHI No/few clouds Low wind speed

  12. Comparison data (MIDAS) Urban London Weather Centre city centre roof top Heathrow airport St James’ Park urban park Rural Wisley 32 km south west Bracknell-Beaufort Park outside of model domain

  13. Temperature: 30-31 July 1999 Heathrow London Weather Centre METRAS METRAS+ BEP St James’ Park

  14. Temperature: all locations, all days

  15. Wind: 7-8 August 1998 wind speed [m/s] wind direction [deg] LWC LHR

  16. Summary of comparison

  17. Analysis of the urban effect Urban effect: model-centric definition result of model run with current land use - result of model run with no urban fraction ---------------------------------------------------------------- effect of the urban area (annihilation approach)

  18. Effect on temperature / UHI T (current urbanisation) – T (rural domain) 4:00 a.m. 12:00 noon ΔT[K] ΔT[K]

  19. Effect on wind speed FF (current urbanisation) – FF (rural domain) 4:00 a.m. 12:00 noon ΔFF[m/s] ΔFF[m/s]

  20. Regional effect REI = total area of affected cells / total area of urban cells≥ 100% based on Trusilova et al. (2008) urban grid cell: any cell with at least 30% urban land use affected grid cell: defined, so that the total urban area is affected any cell with a difference higher than the lowest difference of any urban cell is affected

  21. Regional effect REI = total area of affected cells / total area of urban cells

  22. Conclusions • Implementation of BEP into METRAS improves resultsfor the urban area. • Suitable measurements required in the urban area. • Urban impact on meteorology not limited to the urban area. • High data demand for adequate application of BEP.

  23. Outlook Impact on chemistry Application for urban climate studiesfor Hamburg, Germany Incorporate more detailed informationabout the urban area: - building resolved building heights - street resolved street direction and street width Include direct anthropogenic heat flux.

  24. THE END 17.08.11

  25. Idealised Domain Domain dimensions Size 40 x 40 km2 Resolution 1 x 1 km2 Land use Centre (400 km2) urban Background meadows Meteorological conditions Geostrophic wind speed 4.0 m/s Potential temperature gradient 3.5 K/km

  26. Idealised Domain green: METRASblack: METRAS+BEP yellow: rural Potential Temperature Windspeed TKE

  27. Sensitivity to size of urban area Tpot [K] 6 km 10 km 20 km Distance across domain [km] Extent of urban area: 6km, 10km, 20km

  28. Sensitivity to size of urban area Tpot [K] ΔT = 4.0 K ΔT = 3.5 K ΔT = 3.0 K Distance across domain [km] Extent of urban area: 6km, 10km, 20km

  29. UHI diurnal cycle UHI intensity: Highest temperature difference 'Current land use' – 'rural land use' within the domain REPLACE WITH FIGURE FROM PUBLICATION UHI

  30. Detailed data for Hamburg

  31. Idealised Domain z = 10m z = 30m Potential Temperature

  32. 6-7 August 1998 LHR Heathrow METRAS METRAS+ BEP St James’ Park

  33. LWC: 30-31 July 1999 LWC METRAS+ BEP METRAS

  34. LWC: 6-7 August 1998 METRAS+ BEP LWC METRAS

  35. LHR: 30-31 July 1999 LHR METRAS+ BEP METRAS

  36. LHR: 6-7 August 1998 LHR METRAS+ BEP METRAS

  37. SJP: 6-7 August 1998 METRAS+ BEP SJP METRAS

  38. Urban areas • Model components • Simplified tests • Evaluation and analysis for London • Outlook (Hamburg) 17.08.11

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