Tutorial for Obtaining Forecast Turbulence Parameters for Acoustic Propagation

Turbulence in the atmospheric boundary layer impacts propagation of sound near the surface of earth. This effect presents a challenge in accurately predict noise exposure to sonic booms. New supersonic aircraft noise regulations are being considered due to advances in technology to reduce sonic boom loudness. These regulations will require noise certification flight tests that are likely to include bounds on weather parameters similar to that of subsonic aircraft noise regulations. Obtaining forecasts of turbulence strength prior to takeoff helps ensure that noise certification tests are within limits. Depending on the level of accuracy required, these forecast data or reanalysis data could be used in lieu of or to supplement measurements of turbulence in the field, which would reduce costs and complexity of the measurements. This paper serves as a tutorial for obtaining forecast data of near-surface turbulence from the Climate Forecast System atmospheric model. While the primary application of the tutorial is for supersonic aircraft noise certification and sonic boom propagation, the parameters are broadly applicable for other acoustics problems. The relevant ambient parameters are pressure, temperature, and relative humidity; the turbulence parameters are atmospheric boundary layer height, friction velocity, mixed-layer velocity scale, and surface layer temperature scale.