Post on 26-Mar-2015
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Vertical profiles of the variance of the vertical wind component and
turbulence intensitiesfrom 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
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Large SODARof IMK-IFU(METEK DSDR3x7)
frequency: 1500 Hzrange: 1300 mresolution: 20 mlowestrange gate: ca. 60 m
size of instrument:
height: 4 mwidth: 1,50 mlength: 10 mweight: 8 t
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Measurements from an urban boundary-layer
Hannover, Germanyoverall roughness length: about 1 mlarge SODAR on industrial grounds near a railway stationtypical range: 500 to 700 mtemporal resolution: 30 min
30 m
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Measurements from an urban boundary-layer
Budapest (Hungary) on the western side hills,100 – 200 m above the Danube river, in thewestern outskirts of the town
large SODAR
typical range: 500 to 700 mtemporal resolution: 30 min
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
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 mtemporal resolution: 30 min
nearly flat terrain in Northern Bavaria
MiniSODAR
100 to 150 m10 min
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
mean wind speed
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean vertical profiles of wind speed
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean vertical profilesof wind speed
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean diurnal variation of wind speed
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean diurnal variationof wind speed
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
sigma w
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean vertical profiles of sigma w
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean diurnal variation of sigma w
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean diurnal variationof sigma w
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
turbulence intensity
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean diurnal variation of turbulence intensity
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean vertical profiles of turbulence intensity
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Monthly mean vertical profilesof turbulenceintensity
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
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.
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
0
100
200
300
400
500
Vertical structure of the UBL over Hannover
Ekman-layer
Prandtl-layer
Canopy-layer
Wake-layerurban roughness-layer
m
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
measurements over an airport
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
June/July 2005
The sodar wassituated at no. 6
Paris airportCh. de Gaulle
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
vertical profilesof 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)
S2S4
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
vertical profilesof 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)
S4S2
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
vertical profilesof turbulenceintensity (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
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
mixing-layer height
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Algorithms todetect MLHfrom SODAR data
criterion 1:upper edge
of highturbulence
criterion 2:surface andliftedinversions
MLH = Min (C1, C2)
acoustic backscatter intensity acoustic backscatter intensity
height height
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Algorithms todetect MLHfrom Ceilometer-Daten
criterion
minimal vertical gradientof backscatterintensity (the mostnegative gradient)
optical backscatter intensity vertical gradient ofoptical backscatter intensity
height height
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
comparison of both algorithms
acoustic backscatter intensity
optical backscatter intensity
vertical gradient ofoptical backscatter intensity
heightheightheight
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
optical backscatter intensity
acoustic backscatter intensity
vertical gradient of optical backscatter intensity
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Simultaneous operation SODAR-Ceilometer: examples for summer days
CBLCBL
CBLCBL
SBLSBL
SBLSBL
RLRL
RLRL
RL
RL RL
RL
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,
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
nocturnal inver-sions dominate
CBL tops dominate days with strong winds withoutdiurnal variations
frequency distribution of MLHHannover, Germany, February 2002
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.destefan.emeis@imk.fzk.de
Monthly mean diurnal courses of mixing-layer heightHannover, 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.
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
attempt to derive turbulence exchange coefficientsfrom sodar data
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
The efficiency of vertical transport by turbulent motion isdescribed by the turbulent viscosity t of the flow.
In numerical flow models this turbulent viscosity is calledturbulent 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)
zu
wu
''
zu
za
w
)(
2
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft
IMK-IFU, Stefan Emeis stefan.emeis@imk.fzk.de
Available papers1) 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
2) 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
3) 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