TPD 1

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Coupling of a meteorological model with a sound
propagation model

• Frank van den Berg
• TNO TPD
• Delft, The Netherlands

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Refraction and reflectionwind- and temperature
distribution curved sound rays
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Complex sound propagation path

• Variations of
• Ground type
• Surface temperature
• Wind direction
• Wind and temperature profile
• Humidity

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Long term Goal

• Calculation method to estimate long-term average
  noise contours from shooting noise
• Calculation method to predict the noise load from
  shooting noise for actual meteorological
  situations

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Aim of this study
Meteo model
sound model
now 2d later 3d

• Developing a model which can describe the
  meteorological situation in the wetlands
• Coupling this model with a sound propagation
  model
• Study influence of variations in meteorology on
  sound propagation

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Meso-scale Meteorological model
Grid points in XZ-plane, system constant in Y
direction
Z
Grid z 0 m to 5000 m, 12 points x-150 to 150
km, 300 points
2-dimensional
Y
X
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Meteorological model 2

• Developed by University Amsterdam (VU-Adam)
• Time step 15 sec
• Run from 0600 till 2100 1 hour calculation
  time on PC

Surface sand dune, vegetation, wetlands (tide),
difference between summer and winter.

• For each grid point the model calculates
• wind speed along x, y and z-axis
• potential temperature (C)
• water vapour concentration

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Meteorological model 3
Physics
U,V Pressure gradient, Coriolis, Advection,
Friction W Conservation of mass T,q
Diffusion, Advection, Surface flux
cold
U(t,z,x,W,T,P,? ) V(t,z,x,W,T,P,?) T(t,z,x,U,W,H)
q(t,z,x,U,W,L,E) W(t,z,x,P,U,T)
advection
radiation
evaporation
warm
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Calculation method for sound propagation
Parabolic Equation (PE) method
height z
atmosphere effective sound speed c ct u
absorbing layer
l/10
source
position r
Surface with complex impedance
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Sea breeze

• Circulation with onshore breeze at the surface
• Caused by temp. differences (cold sea and warm
  land)
• In spring and early summer (when there is a weak
  large-scale wind, preferably offshore)

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Coast on cloudless summer day with light
background wind relatively strong sea breeze
that moves inland
temperature
horizontal wind speed
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Calculated Sound field source 1.2 km from coast
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Case study
Continent
Island
Wetlands
Sea
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Small island and no large-scale wind sea breeze
at both sides of the island
temperature
sea land sea
wind speed
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Calculated Sound field source middle of island
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Large island near continent and weak large-scale
wind
sea land sea land
temperature
wind speed
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Calculated Sound field source 1.2 km from coast
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Conclusions

• To describe the sound propagation in the wetlands
  a combination of a meteorological model and a
  sound propagation model is needed
• A coupling of a meteorological meso-scale model
  can be achieved
• To describe realistic situations 3-dimensional
  models are needed.