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Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Vertical profiles of the variance of the vertical.

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Presentation on theme: "Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Vertical profiles of the variance of the vertical."— Presentation transcript:

1 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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

2 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis mean wind speed

7 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean vertical profiles of wind speed

8 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean vertical profiles of wind speed

9 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean diurnal variation of wind speed

10 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis

11 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean diurnal variation of wind speed

12 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis sigma w

13 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean vertical profiles of sigma w

14 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean diurnal variation of sigma w

15 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis

16 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean diurnal variation of sigma w

17 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis turbulence intensity

18 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean diurnal variation of turbulence intensity

19 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean vertical profiles of turbulence intensity

20 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis

21 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Monthly mean vertical profiles of turbulence intensity

22 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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.

23 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Vertical structure of the UBL over Hannover Ekman-layer Prandtl-layer Canopy-layer Wake-layer urban roughness-layer m

24 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis measurements over an airport

25 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis June/July 2005 The sodar was situated at no. 6 Paris airport Ch. de Gaulle

26 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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

27 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis vertical profiles of w (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

28 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis vertical profiles of turbulence intensity (u / w ) CDG S2: influenced by the airport (higher turbu- lence over rough surface) S4: rural profiles (lower turbu- lence over smooth surface) S4 S2

29 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis mixing-layer height

30 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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 height

31 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Algorithms to detect MLH from Ceilometer-Daten criterion minimal vertical gradient of backscatter intensity (the most negative gradient) optical backscatter intensityvertical gradient of optical backscatter intensity height

32 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis comparison of both algorithms acoustic backscatter intensity optical backscatter intensity vertical gradient of optical backscatter intensity height

33 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis optical backscatter intensity acoustic backscatter intensity vertical gradient of optical backscatter intensity

34 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Simultaneous operation SODAR-Ceilometer: examples for summer days CBL SBL RL SBL Emeis, S., K. Schäfer, 2006: Remote sensing methods to investigate boundary-layer structures relevant to air pollution in cities. Bound.-Lay Meteorol., 121, ,

35 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis nocturnal inver- sions dominate CBL tops dominate days with strong winds without diurnal variations frequency distribution of MLH Hannover, Germany, February 2002

36 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis 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,

37 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis attempt to derive turbulence exchange coefficients from sodar data

38 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis The efficiency of vertical transport by turbulent motion is described by the turbulent viscosity t of 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)

39 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis

40 Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft IMK-IFU, Stefan Emeis Available papers 1)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, DOI: / /2001/ Emeis, S., 2004: Vertical wind profiles over an urban area. Meteorol. Z., 13, DOI: / /2004/ )mixing layer height Emeis, S., M. Türk, 2004: Frequency distributions of the mixing height over an urban area from SODAR data. Meteorol. Z., 13, DOI: / /2004/ Emeis, S. and K. Schäfer, 2006: Remote sensing methods to investigate boundary-layer structures relevant to air pollution in cities. Bound-Lay. Meteorol., 121, DOI: /s 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, DOI: / /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: /s )parameterization of turbulent exchange coefficients Emeis, S., 2004: Parameterization of turbulent viscosity over orography. Meteorol. Z., 13, DOI: / /2004/


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