1 / 40

Vertical profiles of the variance of the vertical wind component and turbulence intensities

Vertical profiles of the variance of the vertical wind component and turbulence intensities from sodar soundings in urban measurement campaigns. Stefan Emeis Institute for Meteorology and Climate Research, Dept. Atmospheric Environmental Research (IMK-IFU) Forschungszentrum Karlsruhe GmbH

mechelle-rich
Download Presentation

Vertical profiles of the variance of the vertical wind component and turbulence intensities

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Vertical profiles of the variance of the vertical wind component and turbulence intensities from sodar soundings in urban measurement campaigns Stefan Emeis Institute for Meteorology and Climate Research, Dept. Atmospheric Environmental Research (IMK-IFU) Forschungszentrum Karlsruhe GmbH Garmisch-Partenkirchen, Germany stefan.emeis@imk.fzk.de

  2. Large SODAR of IMK-IFU (METEK DSDR3x7) frequency: 1500 Hz range: 1300 m resolution: 20 m lowest range gate: ca. 60 m size of instrument: height: 4 m width: 1,50 m length: 10 m weight: 8 t

  3. Measurements from an urban boundary-layer Hannover, Germany overall roughness length: about 1 m large SODAR on industrial grounds near a railway station typical range: 500 to 700 m temporal resolution: 30 min 30 m

  4. Measurements from an urban boundary-layer Budapest (Hungary) on the western side hills, 100 – 200 m above the Danube river, in the western outskirts of the town large SODAR typical range: 500 to 700 m temporal resolution: 30 min

  5. Measurements from rural boundary-layers flat terrain (Fürstenfeldbruck (FFB), alpine foreland) complex terrain (Black Forest, at a sattle point on a crest line) roughness length: FFB: a few cm, Black Forest about 1 m large SODAR typical range: 500 to 700 m temporal resolution: 30 min nearly flat terrain in Northern Bavaria MiniSODAR 100 to 150 m 10 min

  6. mean wind speed

  7. Monthly mean vertical profiles of wind speed

  8. Monthly mean vertical profiles of wind speed

  9. Monthly mean diurnal variation of wind speed

  10. Monthly mean diurnal variation of wind speed

  11. sigma w

  12. Monthly mean vertical profiles of sigma w

  13. Monthly mean diurnal variation of sigma w

  14. Monthly mean diurnal variation of sigma w

  15. turbulence intensity

  16. Monthly mean diurnal variation of turbulence intensity

  17. Monthly mean vertical profiles of turbulence intensity

  18. Monthly mean vertical profiles of turbulence intensity

  19. Conclusions for the urban boundary layer The variances of the vertical velocity component are about 30% higher than over rural terrain. In the afternoon the variance is increasing considerably with height, in summer up to about 350 m above ground, in winter up to about 200 m. This feature is not found over rural terrain. In summer and autumn the variance is increasing with height even at night-time, which it does not over rural terrain. The turbulence intensity at night-time is double as high as over rural terrain. The daytime increase in turbulence intensity is larger than over rural terrain. This indicates a stronger heating of the urban surface. The turbulence intensity is highest at 60 m agl, at night-time it is up to 50% larger than the turbulence intensity at 210 m agl. The nocturnal decrease of the turbulence intensity with height is much stronger than over rural terrain. Also, we find that the wind speed at 60 m agl is nearly constant all the day, whereas over flat rural terrain it shows an increase around noon.

  20. Vertical structure of the UBL over Hannover m 500 400 Ekman-layer 300 200 Prandtl-layer 100 Wake-layer urban roughness-layer Canopy-layer 0

  21. measurements over an airport

  22. Paris airport Ch. de Gaulle June/July 2005 The sodar was situated at no. 6

  23. vertical profiles of wind speed u CDG June/July 2005 S2: influenced by the airport (lower wind speed over rough surface) S4: rural profiles (higher wind speed over smooth surface) S2 S4

  24. vertical profiles of sw (variance of vertical wind speed, a measure for turbulence) S2: influenced by the airport (higher turbu- lence over rough surface) S4: rural profiles (lower turbu- lence over smooth surface) S4 S2

  25. vertical profiles of turbulence intensity (u / sw) CDG S2: influenced by the airport (higher turbu- lence over rough surface) S4: rural profiles (lower turbu- lence over smooth surface) S4 S2

  26. mixing-layer height

  27. height height Algorithms to detect MLH from SODAR data criterion 1: upper edge of high turbulence criterion 2: surface and lifted inversions MLH = Min (C1, C2) acoustic backscatter intensity acoustic backscatter intensity

  28. height height Algorithms to detect MLH from Ceilometer-Daten criterion minimal vertical gradient of backscatter intensity (the most negative gradient) optical backscatter intensity vertical gradient of optical backscatter intensity

  29. height height height comparison of both algorithms optical backscatter intensity vertical gradient of optical backscatter intensity acoustic backscatter intensity

  30. acoustic backscatter intensity optical backscatter intensity vertical gradient of optical backscatter intensity

  31. Simultaneous operation SODAR-Ceilometer: examples for summer days RL RL RL RL CBL CBL SBL SBL SBL SBL RL RL RL RL CBL CBL SBL SBL SBL SBL Emeis, S., K. Schäfer, 2006: Remote sensing methods to investigate boundary-layer structures relevant to air pollution in cities. Bound.-Lay Meteorol., 121, 377-385,

  32. frequency distribution of MLH Hannover, Germany, February 2002 nocturnal inver- sions dominate days with strong winds without diurnal variations CBL tops dominate

  33. Monthly mean diurnal courses of mixing-layer height Hannover, Germany 2002/03 Emeis, S., M. Türk, 2004: Frequency distributions of the mixing height over an urban area from SODAR data. Meteorol. Z., 13, 361-367. stefan.emeis@imk.fzk.de

  34. attempt to derive turbulence exchange coefficients from sodar data

  35. The efficiency of vertical transport by turbulent motion is described by the turbulent viscosity tof the flow. In numerical flow models this turbulent viscosity is called turbulent exchange coefficient. t = - or approximated by sodar data  a(z) = 1.6 (0-200 m), 2.0 (200 – 600 m), 2.5 (600 – 1000 m)

  36. Available papers • wind profiles • Emeis, S., 2001: Vertical variation of frequency distributions of wind speed in and above the surface layer observed by sodar. • Meteorol. Z., 10, 141-149. DOI: 10.1127/0941-2948/2001/0010-0141 • Emeis, S., 2004: Vertical wind profiles over an urban area. Meteorol. Z., 13, 353-359. DOI: 10.1127/0941-2948/2004/0013-0353 • mixing layer height • Emeis, S., M. Türk, 2004: Frequency distributions of the mixing height over an urban area from SODAR data. Meteorol. Z., 13, 361-367. • DOI: 10.1127/0941-2948/2004/0013-0361 • Emeis, S. and K. Schäfer, 2006: Remote sensing methods to investigate boundary-layer structures relevant to air pollution in cities. • Bound-Lay. Meteorol., 121, 377-385. DOI: 10.1007/s10546-006-9068-2 • Schäfer, K., S. Emeis, H. Hoffmann, C. Jahn, 2006: Influence of mixing layer height upon air pollution in urban and sub-urban areas. • Meteorol. Z., 15, 647-658. DOI: 10.1127/0941-2948/2006/0164 • Piringer, M., S. Joffre, A. Baklanov, A. Christen, M. Deserti, K. De Ridder, S. Emeis, P. Mestayer, M. Tombrou, D. Middleton, • K. Baumann-Stanzer, A. Dandou,A. Karppinen, J. Burzynski, 2007: The surface energy balance and the mixing height in urban areas – • activities and recommendations of COST-Action 715. Published online in Bound.-Lay. Meteorol. DOI: 10.1007/s10546-007-9170-0 • parameterization of turbulent exchange coefficients • Emeis, S., 2004: Parameterization of turbulent viscosity over orography. Meteorol. Z., 13, 33-38. DOI: 10.1127/0941-2948/2004/0013-0033

More Related