Atmospheric Acoustic Remote Sensing: Principles and Applications
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Summary
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.
Table of Contents
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
Editorial Reviews
". . . Atmospheric Acoustic Remote Sensing is a welcome contribution to the field of acoustic remote sensing."
– Gilles A. Daigle, National Research Council of Canada, in Physics Today, Dec 2008
