Coherent Doppler Wind Lidars in a Turbulent Atmosphere

by Victor Banakh

Overview

Radio-physical tools for measuring atmospheric dynamics include sodars, Doppler radars, and Doppler lidars. Among these, coherent Doppler lidars (CDLs) have been considered the best for remote measurement of wind turbulence. This is important not only for understanding the exchange processes in the boundary layer, but also in the applied aspect, such as aviation safety. CDLs significantly extend possibilities of experimental investigation of not only wind turbulence, but also coherent structures such as aircraft wake vortices. The authors of this book conducted field tests of the developed methods of lidar measurements of wind velocity, atmospheric turbulence parameters, and aircraft wake vortices. This valuable resource, containing over 500 equations based on original results from the authors' work, gives professionals a comprehensive description of the operating principles of continuous wave and pulsed coherent Doppler lidars. This book studies the possibilities of obtaining information about wind turbulence from data measured by continuous wave and pulsed CDLs. The procedures for estimation are described, as well as algorithms for numerical simulation. Results on the vortex behavior and evolution are then presented.

Product Details

ISBN-13:	9781608076673
Publisher:	Artech House, Incorporated
Publication date:	08/28/2013
Pages:	248
Product dimensions:	7.20(w) x 10.20(h) x 0.90(d)

Table of Contents

Preface ix

Introduction xi

References xvii

Chapter 1 Statistics of CDL Echo Signal 1

1.1 Introduction 1

1.2 Coherent Detection and Governing Equations for CDL Echo Signals 2

1.3 Echo Signal Statistics for Continuous-Wave CDLs 10

1.3.1 Statistical Characteristics of Echo Signal of Continuous-Wave CDLs 15

1.3.2 One-Dimensional Probability Density Functions of the Amplitude and Power of the Echo Signal of Continuous-Wave CDLs 19

1.4 Echo Signal Statistics for Pulsed CDLs 23

1.4.1 Statistical Characteristics of the Echo Signals of Pulsed CDLs 26

1.4.2 Influence of Turbulent Fluctuations of the Refractive Index of Air on Echo Signal Power Statistics 27

1.5 Conclusions 34

References 35

Chapter 2 Statistics of Lidar Estimates of the Radial Velocity and Doppler Spectrum Width 41

2.1 Introduction 41

2.2 Estimation of Spectral Moments 42

2.2.1 Weighting Functions of Averaging over the Sensing Volume 42

2.2.2 Estimation Algorithms 48

2.3 Statistical Characteristics of Estimates of the Radial Velocity and the Doppler Spectrum Width for Continuous-Wave CDLs 51

2.3.1 Variance of the Lidar Estimate of Radial Velocity and Mathematical Expectation of the Squared Width of the Doppler Spectrum 52

2.3.2 Temporal Structure Function and Spectrum of Wind Velocity Measured with a Continuous-Wave CDL 57

2.4 Error in Estimation of the Radial Velocity from Continuous-Wave CDL Data 63

2.5 Influence of Turbulent Fluctuations of the Refractive Index on the Temporal Spectrum of Wind Velocity Measured by Continuous-Wave CDL 71

2.6 Statistics for Radial Velocity Estimates and the Width of the Doppler Spectrum for Pulsed CDLs 77

2.7 Conclusions 85

References 86

Chapter 3 Measuring the Wind Velocity and Direction with Coherent Doppler Lidars 91

3.1 Introduction 91

3.2 Measurement of Mean Wind Velocity and Direction with a Continuous-Wave CDL 93

3.3 Methods for Estimating the Wind Velocity Vector from Pulsed CDL Data 102

3.3.1 Method of Filtered Sine Wave Fitting (FSWF) 103

3.3.2 Maximum of the Function of Accumulated Spectra (MFAS) Method 104

3.3.3 Wind Vector Maximum Likelihood (WVML) Method 105

3.3.4 Cramer-Rao Lower Bound 106

3.3.5 Analysis of the Accuracy of Wind Velocity Vector Estimation Techniques Based on Numerical Simulations 107

3.4 Experimental Testing of the FSWF and MFAS Techniques 112

3.5 Simulation of Retrieval of Vertical Wind Profiles from Measurements by Spaceborne CDLs 116

3.6 Conclusions 121

References 123

Chapter 4 Estimation of Atmospheric Turbulence Parameters from Wind Measurements with Coherent Doppler Lidars 127

4.1 Introduction 127

4.2 Estimation of Wind Turbulence Parameters from Doppler Spectrum Width and Temporal Statistics of Radial Velocity Measured with Continuous-Wave CDLs 129

4.3 Determination of the Turbulent Energy Dissipation Rate from the Transverse Spatial Structure Function of Radial Velocity Measured by Conically Scanning Continuous-Wave CDLs 135

4.4 Retrieval of Vertical Profiles of the Turbulent Energy Dissipation Rate from Continuous-Wave CDL Data 139

4.5 Methods for Estimating Wind Turbulence Parameters from Pulsed CDL Scanning Data in the Vertical Plane 143

4.6 Experimental Studies of the Possibility of Turbulence Measurements by Pulsed CDLs in the Atmospheric Boundary Layer 150

4.6.1 Comparison of Lidar Estimates of the Turbulent Energy Dissipation Rate with Data from Sonic Anemometers 156

4.7 Estimation of the Turbulence Energy Dissipation Rate from Data Measured with a Conically Scanning Pulsed CDL 162

4.8 Simulation of Clear Air Turbulence Detection by Coherent Doppler Lidars 168

4.9 Conclusions 172

References 175

Chapter 5 Lidar Investigations of Aircraft Wake Vortices 179

5.1 Introduction 179

5.2 Influence of Aircraft Wake Vortices on the Form of Doppler Spectra: Velocity Envelopes and Integration Method 181

5.3 Measurement of Wake Vortex Parameters Using a Continuous-Wave CDL 188

5.4 Measurement of Wake Vortex Parameters Using a Pulsed CDL 191

5.5 Comparative Analysis of the Results of Simultaneous Measurements of Wake Vortex Parameters Using Pulsed and Continuous-Wave Lidars 195

5.6 Measurements of Wake Vortex Parameters in the Atmospheric Surface Layer 203

5.7 Lidar Investigations of the Influence of Wind and Atmospheric Turbulence on Wake Vortices in the Atmospheric Boundary Layer 205

5.8 Measurement of Wake Vortex Parameters Using an Airborne Lidar in the Free Atmosphere 211

5.9 Lidar Investigations of a Wind Turbine Wake 222

5.10 Conclusions 228

References 230

List of Acronyms 235

Nomenclature 236

About the Authors 243

Index 245