Effects of Meteorology on propogation

Abstract – Honington 2001

A fundamental investigation of the effects of range-dependent meteorology on outdoor sound propagation

• Field campaigns
  • Experimental techniques
  • SODAR
  • LIDAR
• Comparisons with predictions
• Limitations in theoretical modelling

Introduction

• Influence of weather on a particular measurement depends upon the determination of the prevailing meteorological conditions over the propagation path
• Application of research into outdoor noise propagation to practical environmental noise measurement and prediction
• Three principal mechanisms of refraction, atmospheric absorption and scattering

Schematic of Field Trial

Experimental Method: Meteorology

• Wind profiles
  • SODAR
    • 250 metres along array
  • Doppler LIDAR
    • Scanning in three-dimensions
    • Radial wind velocities from a single location
    • 900 metres perpendicular array
  • Radar wind profiler
    • 28km southeast of site
    • Augment data at highest altitudes
• Automatic weather stations
  • 2m and 10m at source and furthest position

Aerial view of bunker trial

Multi-Azimuth Parabolic Equation Predictions

Conclusion

• Meteorological changes may exert significant influence
  • High-level sources and long distances
• Downwind
  • Noise levels may increase by a few dB
  • Depends on wind speed
• Measurement normally preferred downwind
  • More conservative since deviation is smaller
• Upwind or sidewind level
  • Decreases in excess of 20 dB
• Temperature gradients under with no wind
  • Variations of same order as strong vector winds

Acknowledgements

• The SODAR team was led by Prof Bradley and Prof Collier led the LIDAR team
• We would like to thank D Humpheson and R Beaman of RAF Henlow, Group Captain Anderton of RAF Honington, and CL Murray of QinetiQ Malvern
• This work was kindly funded by the EPSRC under grant GR/M71459

Contact

Dr David Waddington