Atmospheric Acoustic Remote Sensing

Sonic Detection and Ranging (SODAR) systems and Radio Acoustic Sounding Systems (RASS) use sound waves to determine wind speed, wind direction, and turbulent character of the atmosphere. They are increasingly used for environmental and scientific applications such as analyzing ground-level pollution dispersion and monitoring conditions affecting wind energy generation. However, until now there have been no reliable references on SODAR and RASS for practitioners in the field as well as non-experts who wish to understand and implement this technology to their own applications. Authored by an internationally known expert in the design and use of SODAR/RASS technology, Atmospheric Acoustic Remote Sensing: Principles and Applications systematically explains the underlying science, principles, and operational aspects of acoustic radars. Abundant diagrams and figures, including eight pages of full-color images, enhance clear guidelines and tools for handling calibration, error, equipment, hardware, sampling, and data analysis. The final chapter explores applications in environmental research, boundary layer research, wind power and loading, complex terrain, and sound speed profiles. Atmospheric Acoustic Remote Sensing offers SODAR and RASS users as well as general remote sensing practitioners, environmental scientists, and engineers a straightforward guide for using SODARs to perform wind measurements and data analysis for scientific, environmental, or alternative monitoring applications.

What Is Atmospheric Acoustic Remote Sensing? Direct Measurements and Remote Measurements How Can Measurements Be Made Remotely? Passive and Active Remote Sensing Some History Why Use Acoustics? Direct Sound Propagation from a Source to a Receiver Acoustic Targets Creating Our Own Target Modern Acoustic Remote Sensing Applications Where to, from Here? The Atmosphere Near the Ground Temperature Profiles Near the Surface Wind Profiles Near the Surface Richardson Number The Prandtl Number The Structure of Turbulence Monin-Oboukhov Length Similarity Relationships Profiles of and Probability Distribution of Wind Speeds Sound in the Atmosphere Basics of Sound Waves Frequency Spectra Background and System Noise Reflection and Refraction Diffraction Doppler Shift Scattering Attenuation Sound Propagation Horizontally Sound Transmission and Reception Geometric Objective of SODAR Design Speakers, Horns, and Antennas Monostatic and Bistatic SODAR Systems Doppler Shift from Monostatic and Bistatic SODARs Beam Width Effects on Doppler Shift Continuous and Pulsed Systems Geometry of Scattering The Acoustic Radar Equation Acoustic Baffles Frequency-Dependent Form of the Acoustic Radar Equation Obtaining Wind Vectors Multiple Frequencies Pulse Coding Methods SODAR Systems and Signal Quality Transducer and Antenna Combinations SODAR Timing Basic Hardware Units Data Availability Loss of Signal in Noise Calibration SODAR Signal Analysis Signal Acquisition Detecting Signals in Noise Consistency Methods Turbulent Intensities Peak Detection Methods of AeroVironment and Metek Robust Estimation of Doppler Shift from SODAR Spectra Averaging to Improve SNR Spatial and Temporal Separation of Sampling Volumes Sources of Measurement Error A Model for SODAR Response to a Prescribed Atmosphere RASS Systems RADAR Fundamentals Reflection of RADAR Signals from Sound Waves Estimation of Measured Height Deduction of Temperature Wind Measurements Turbulent Measurements RASS Designs Antennas Limitations Applications Review of Selected Applications Environmental Research Boundary Layer Research Wind Power and Loading Complex Terrain Sound Speed Profiles Hazards Appendix 1: Mathematical Background Appendix 2: Sample Data Sets and Matlab Code Appendix 3: Available Systems Appendix 4: Acoustic Travel Time Tomography Appendix 5: Installation of a SODAR or RASS Index