Kein Folientitel

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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.emei
s_at_imk.fzk.de
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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
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Measurements from an urban boundary-layer Hannove
r, 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
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Measurements from an urban boundary-layer Budapes
t (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
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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
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mean wind speed
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Monthly mean vertical profiles of wind speed
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Monthly mean vertical profiles of wind speed
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Monthly mean diurnal variation of wind speed
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Monthly mean diurnal variation of wind speed
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sigma w
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Monthly mean vertical profiles of sigma w
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Monthly mean diurnal variation of sigma w
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Monthly mean diurnal variation of sigma w
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turbulence intensity
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Monthly mean diurnal variation of turbulence
intensity
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Monthly mean vertical profiles of turbulence
intensity
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Monthly mean vertical profiles of
turbulence intensity
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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.
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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
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measurements over an airport
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Paris airport Ch. de Gaulle
June/July 2005 The sodar was situated at no. 6
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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
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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
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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
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mixing-layer height
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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
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height
height
Algorithms to detect MLH from Ceilometer-Daten cr
iterion minimal vertical gradient of
backscatter intensity (the most negative gradient)
optical backscatter intensity
vertical gradient of optical backscatter intensity
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height
height
height
comparison of both algorithms
optical backscatter intensity
vertical gradient of optical backscatter
intensity
acoustic backscatter intensity
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acoustic backscatter intensity
optical backscatter intensity
vertical gradient of optical backscatter intensity
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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,
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frequency distribution of MLH Hannover, Germany,
February 2002
nocturnal inver- sions dominate
days with strong winds without diurnal variations
CBL tops dominate
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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_at_imk.fzk.de
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attempt to derive turbulence exchange
coefficients from sodar data
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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)
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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,