Meteorological influences on the noise reduction potential of forests

Transcription

1 Fakultät Umweltwissenschaften, Fachrichtung Hydrowissenschaften, Institut für Hydrologie und Meteorologie Meteorological influences on the noise reduction potential of forests Astrid Ziemann 1, D. Keith Wilson 2 1) Technische Universität Dresden, Professur für Meteorologie 2) U.S. Army Engineer Research and Development Center, Hanover DAGA 2014 Oldenburg

2 Meteorological influence on measured sound level Gradient effective sound speed [1/s] Introduction :00 20:00 00:00 16:00 20:00 00:00 04:00 08: Time [CET] Sound level [db] 1000 Hz Distance from source: 143 m Correlation between vertical gradient (10-2 m height) of effective sound speed (temperature and wind vector) and sound level

3 Scheme of model area: Strip of forest Methods Modeled forest: Strip of different (homogeneous) forests within homogeneous grassland, bushes and young forest at the edges

4 Simulation of meteorological quantities , 12 CET, decidious forest Horizontal wind velocity in m/s Air temperature in K PAD Wind [1/m] Results Atmospheric boundary layer model HIRVAC HIgh Resolution Vegetation Atmosphere Coupler

5 Simulation of vertical sound speed gradients Height [m] , 12 CET, upwind of forest (grassland) Gradient c eff [1/s] Results upward refraction downward refraction upwind downwind grass

6 Simulation of vertical sound speed gradients Height [m] , 12 CET, inside forest Gradient c eff [1/s] Results upward refraction downward refraction upwind downwind forest upwind downwind grass

7 Simulation of vertical sound speed gradients Height [m] , 12 CET, downwind of forest Gradient c eff [1/s] Results upward refraction downward refraction upwind downwind grass upwind downwind forest upwind downwind grass

8 Methods Scheme of model area: Strip of forest

9 Simulation of sound attenuation Sound frequency=500 Hz Sound attenuation [db] Time downwind: upwind: Results 48 m distance 164 m distance Sound attenuation [db] Time Sound wave model CNPE (after Wilson et al., 2012, InterNoise)

10 Simulation of sound attenuation Sound frequency=500 Hz Sound attenuation [db] Results downwind 48 m distance 164 m distance upwind Sound attenuation [db] Red: decidious forest, Green: coniferious forest, Black: Grassland Increased sound atttenuation for upwind conditions (besides decidious forest, large distance from source) Daily variability depending on scenario, distance, wind direction Increasing differences between scenarios with increasing distance

11 Simulation of sound attenuation Sound frequency=63 Hz Sound attenuation [db] m distance 164 m distance downwind upwind Sound attenuation [db] Red: decidious forest, Green: coniferious forest, Black: Grassland Increased sound atttenuation for upwind conditions (besides decidious forest, small distance from source) Maximal daily variability during summer and for upwind conditions Increasing differences between scenarios with increasing distance Results

12 Measurements Clearing-Forest August/September 2011 Tharandt Forest near Dresden

13 Scheme of model area: Clearing inside forest Downwind Upwind Inhomogeneous forest Clearing Inhomogeneous forest Methods Cross section west east adapted to measurements of plant area density within Tharandt forest

14 Comparison of sound attenuation: Simulation and measurement Sound attenuation [db] Simulation downwind upwind clearing/forest frequency: 63 Hz 48 m distance 164 m distance 8.2 Measurements Time Sound attenuation [db] Time downwind: evening-morning, upwind: during daytime Higher attenuation inside forest due to direct vegetation influences Results

15 Measurements inside forest (Old spruce stand) August 2012 Sound source

16 Comparison of attenuation: Clearing and forest Averaged sound attenuation between R1 (ca. 26 m from source) and R2/ Distance between R1 and R2 (ca. 48 m) Sound attenuation [db/m] Clearing Frequency [Hz] Geometrical attenuation Sound attenuation [db/m] Frequency [Hz] Geometrical attenuation forest :00 04:00 08:00 12:00 16:00 20:00 24:00 Time :00 04:00 08:00 12:00 16:00 20:00 24:00 Time Higher sound attenuation for higher sound frequencies inside forest Diffference forest-grass 500 Hz: 0.08 db/m, 1000 Hz: 0.37 db/m Results

17 Summary and Conculsions Different vertical profiles of temperature and wind velocity within forest and over grassland -> influence on sound propagation Increasing daily and yearly variation of sound attenuation and differences between upwind and downwind with increasing sound frequency and distance Maximal sound attenuation for downwind conditions due to forest meteorology: Attenuation of 1-2 db for 63 Hz (in comparison to grassland) Attenuation of 1-12 db for 500 Hz (in comparison to grassland) Summary

18 Thank you for your attention