Atmospheric Acoustic Remote Sensing - Chapter 1 ppt

Atmospheric Acoustic Remote Sensing © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:06:59 PM ATMOSPHERIC ACOUSTIC REMOTE SENSING STUART BRADLEY Stuart Bradley CRC Press Taylor & Francis Group Boca Raton London New York Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business Taylor & Francis Group, an informa business © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:06:59 PM CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2008 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S Government works Printed in the United States of America on acid-free paper 10 International Standard Book Number-13: 978-0-8493-3588-4 (Hardcover) This book contains information obtained from authentic and highly regarded sources Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use The Authors and Publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint Except as permitted under U.S Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers For permission to photocopy or use material electronically from this work, please access www copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc (CCC) 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400 CCC is a not-for-profit organization that provides licenses and registration for a variety of users For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe Library of Congress Cataloging-in-Publication Data Bradley, Stuart Atmospheric acoustic remote sensing / author, Stuart Bradley p cm Includes bibliographical references and index ISBN 978-0-8493-3588-4 (hardback : alk paper) Atmosphere Remote sensing Echo sounding I Title QC871.B73 2006 551.5028’4 dc22 2007034585 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:07:00 PM Contents Preface xi Acknowledgments xiii Author xv Symbol List xvii Chapter What Is Atmospheric Acoustic Remote Sensing? 1.1 Direct Measurements and Remote Measurements 1.2 How Can Measurements Be Made Remotely? 1.3 Passive and Active Remote Sensing 1.4 Some History 1.5 Why Use Acoustics? 1.6 Direct Sound Propagation from a Source to a Receiver 1.7 Acoustic Targets 1.8 Creating Our Own Target 1.9 Modern Acoustic Remote Sensing 1.10 Applications 1.11 Where to from Here? References Chapter 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 The Atmosphere Near the Ground 11 Temperature Profiles near the Surface 11 Wind Profiles near the Surface 13 Richardson Number 16 The Prandtl Number 17 The Structure of Turbulence 18 Monin-Oboukhov Length .20 Similarity Relationships 20 2 Profiles of C T and CV 22 2.9 Probability Distribution of Wind Speeds 23 2.10 Summary 23 References 25 Chapter 3.1 3.2 3.3 3.4 3.5 3.6 Sound in the Atmosphere 27 Basics of Sound Waves 27 Frequency Spectra 30 Background and System Noise 32 Reflection and Refraction 34 Diffraction 36 Doppler Shift 37 v © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:07:09 PM vi Atmospheric Acoustic Remote Sensing 3.7 Scattering 39 3.7.1 Scattering from Turbulence 39 3.7.2 Intensity in Terms of Structure Function Parameters 43 3.7.3 Scattering from Rain 44 3.8 Attenuation 47 3.8.1 Losses Due to Spherical Spreading 47 3.8.2 Losses Due to Absorption 47 3.8.3 Losses Due to Scattering out of the Beam 48 3.9 Sound Propagation Horizontally 51 3.10 Summary 52 References 53 Chapter Sound Transmission and Reception 55 4.1 4.2 Geometric Objective of SODAR Design 55 Speakers, Horns, and Antennas 56 4.2.1 Speaker Polar Response 56 4.2.2 Dish Antennas 57 4.2.3 Phased Array Antennas 61 4.2.4 Antenna Shading 66 4.2.5 Receive Phasing 69 4.2.6 Reflectors 70 4.3 Monostatic and Bistatic SODAR Systems 71 4.4 Doppler Shift from Monostatic and Bistatic SODARs 73 4.5 Beam Width Effects on Doppler Shift 82 4.6 Continuous and Pulsed Systems 83 4.7 Geometry of Scattering 89 4.8 The Acoustic Radar Equation .90 4.9 Acoustic Baffles 91 4.10 Frequency-Dependent Form of the Acoustic Radar Equation 96 4.11 Obtaining Wind Vectors .97 4.12 Multiple Frequencies 100 4.13 Pulse Coding Methods 100 4.14 Summary 103 References 103 Chapter 5.1 SODAR Systems and Signal Quality 105 Transducer and Antenna Combinations 105 5.1.1 Speakers and Microphones 105 5.1.2 Horns 108 5.1.3 Phased-Array Frequency Range 109 5.1.4 Dish Design 110 5.1.5 Designing for Absorption and Background Noise 111 5.1.6 Rejecting Rain Clutter 112 5.1.7 How Much Power Should Be Transmitted? 114 © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:07:10 PM Contents vii 5.2 SODAR Timing 115 5.2.1 Pulse Shape, Duration, and Repetition 115 5.2.2 Range Gates 117 5.3 Basic Hardware Units 120 5.3.1 The Basic Components of a SODAR Receiver 120 5.3.2 Microphone Array 120 5.3.3 Low-Noise Amplifiers 121 5.3.4 Ramp Gain 122 5.3.5 Filters 123 5.3.6 Mixing to Lower Frequencies (Demodulation) 123 5.3.7 Switching from Transmit to Receive, and Antenna Ringing 126 5.4 Data Availability 127 5.4.1 The Highest Useful Range 127 5.5 Loss of Signal in Noise 128 5.5.1 Loss of Signal Due to Beam Drift 132 5.6 Calibration 134 5.6.1 Why Are Calibrations Required? 134 5.6.2 Effective Beam Angle 137 5.6.3 What Accuracy Is Required? 138 5.6.4 Calibrations against Various Potential Standards 138 5.6.5 The PIE Field Campaign Setup 140 5.6.6 Raw SODAR Data versus Mast 141 5.6.7 Numerical Filtering of Data 143 5.6.8 Correlation Method 145 5.6.9 Distribution of Wind Speed Data 147 5.6.10 Regression Slope 149 5.6.11 Variations with Height 152 5.6.12 Wind Direction Regressions 154 5.7 Summary 154 References 156 Chapter 6.1 6.2 6.3 SODAR Signal Analysis 157 Signal Acquisition 157 6.1.1 Sampling 157 6.1.2 Aliasing 157 6.1.3 Mixing 158 6.1.4 Windowing and Signal Modulation 160 6.1.5 Dynamic Range 160 Detecting Signals in Noise 162 6.2.1 Height of the Peak above a Noise Threshold 162 6.2.2 Constancy over Several Spectra 162 6.2.3 Not Generally Being at Zero Frequency 163 6.2.4 Shape 163 6.2.5 Scaling with Transmit Frequency 164 Consistency Methods 164 © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:07:11 PM viii Atmospheric Acoustic Remote Sensing 6.4 Turbulent Intensities 166 6.4.1 Second Moment Data 167 6.5 Peak Detection Methods of AeroVironment and Metek 168 6.5.1 AeroVironment 168 6.5.2 Metek 168 6.6 Robust Estimation of Doppler Shift from SODAR Spectra 170 6.6.1 Fitting to the Spectral Peak 170 6.6.2 Estimation of w 174 6.7 Averaging to Improve SNR 175 6.7.1 Variance in Wind Speed and Direction over One Averaging Period 176 6.7.2 Combining Wind Data from a Number of Averaging Periods 177 6.7.3 Different Averaging Schemes for SODAR and Standard Cup Anemometers 180 6.7.4 Calculating Wind Components from Incomplete Beam Data 182 6.7.5 Which Gives Less Uncertainty: A 3-Beam or a 5-Beam System? 183 6.8 Spatial and Temporal Separation of Sampling Volumes 185 6.9 Sources of Measurement Error 188 6.9.1 Height Estimation Errors 188 6.9.2 Errors in Beam Angle 189 6.9.3 Out-of-Level Errors 190 6.9.4 Bias Due to Beam Spread 190 6.9.5 Beam Drift Effects 190 6.10 A Model for SODAR Response to a Prescribed Atmosphere 193 6.11 Summary 195 References 195 Chapter RASS Systems 197 7.1 7.2 7.3 7.4 RADAR Fundamentals 197 Reflection of RADAR Signals from Sound Waves 198 Estimation of Measured Height 201 Deduction of Temperature 202 7.4.1 Doppler-RASS 202 7.4.2 Bragg-RASS 203 7.5 Wind Measurements 204 7.6 Turbulance Measurements 204 7.7 RASS Designs .204 7.8 Antennas .206 7.8.1 Baffles 207 7.9 Limitations 207 7.9.1 Range .208 7.9.2 Temperature .208 7.10 Summary 211 References 211 © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:07:12 PM Contents Chapter ix Applications 213 8.1 Review of Selected Applications 213 8.1.1 Environmental Research 213 8.1.2 Boundary Layer Research 215 8.1.3 Wind Power and Loading 217 8.1.4 Complex Terrain 217 8.1.5 Sound Speed Profiles 220 8.1.6 Hazards 222 8.2 Summary 223 References 224 Appendix Mathematical Background 227 A1.1 A1.2 A1.3 A1.4 Complex Exponentials 227 Fourier Transforms 228 Autocorrelation and Convolution 230 Least-squares Fitting 232 Appendix Sample Data Sets and Matlab Code 235 Appendix Available Systems 237 A3.1 AeroVironment Inc [California, USA] 237 A3.2 AQ Systems [Stockholm, Sweden] 237 A3.2.1 AQ500 SODAR 237 A3.3 Atmospheric Research Pty Inc [Canberra, Australia] 238 A3.4 Atmospheric Research and Technology LLC (ART) [Hawaii, USA] and Kaijo Corporation [Tokyo, Japan] 239 A3.5 Atmospheric Systems Corporation (ASC) [California, USA] 239 A3.6 METEK GmbH [Elmshorn, Germany] .240 A3.7 REMTECH SA [France] 241 A3.8 Scintec GmbH [Tübingen, Germany] 242 Appendix Acoustic Travel Time Tomography 247 Appendix Installation of a SODAR or RASS 249 A5.1 Guidelines for the Use of Sodar in Wind Energy Resource Assessment 249 A5.1.1 Calibration and Testing 249 A5.1.2 Operating Requirements 250 A5.1.2.1 Temperature 251 A5.1.2.2 Precipitation 251 A5.1.2.3 Vertical Range and Resolution 251 A5.1.2.4 Reliability Criteria 252 © 2008 by Taylor & Francis Group, LLC 3588.indb 11/27/07 4:07:12 PM x Atmospheric Acoustic Remote Sensing A5.1.3 Siting and Noise 253 A5.1.3.1 Acoustic Noise (Passive and Active) 253 A5.1.3.2 Electronic Noise 254 A5.1.3.3 Public Annoyance 254 A5.1.4 Power Supply and Site Documentation 254 A5.1.5 Data Collection and Processing 255 A5.1.5.1 Data Parameters and Sampling/Recording Intervals 255 A5.1.5.2 Calculation of Wind Shear 255 A5.1.5.3 Measurement Period 256 A5.1.5.4 Exclusion of Precipitation Periods 257 A5.1.6 Comparisons with Mechanical Anemometry 257 A5.1.7 Other Considerations for Incorporating SODAR Information into a Resource Assessment Program 258 A5.2 Analysis of The AeroVironment 4000 SODAR Data Processing Methods .260 A5.2.1 Parameter settings 260 A5.2.2 Interrelations of Parameters and Conditions for Parameter Values 260 A5.2.3 Use of an Artificial Signal to Verify Performance 261 References 265 © 2008 by Taylor & Francis Group, LLC 3588.indb 10 11/27/07 4:07:13 PM Preface In 2001 I was contacted by a consortium of research institutions and wind energy interests with a request to provide some background information on the operational characteristics of acoustic radars or SODARs The consortium partners had set up and been funded for an European EU project to evaluate SODARs as a tool in monitoring wind flows at wind turbine sites They felt reasonably confident in their knowledge of SODARs and had purchased some instruments, but wanted to be able to consult on any more complex issues which arose Ultimately this developed into a relatively simple contract in which my colleague at the University of Salford, Sabine von Hünerbein, and I delivered an intensive two-day short course on SODARs to a small group of scientists and engineers at ECN headquarters in Amsterdam There were two aspects of this short course which impressed themselves upon me The first was the volume of information required to adequately cover the principles of operation and data interpretation for SODARs performing wind measurements in the atmospheric boundary layer The second aspect was that intelligent and extremely technically capable people, already working in the area of wind measurement, did not adequately obtain enough information about remote sensing instruments from manufacturers’ information manuals and data sheets The initial interaction with the ‘WISE’ EU consortium led to Sabine and me being responsible for overseeing the major calibration work-package in the project The final report from the group working on that work-package was arguably the most comprehensive investigation of SODAR-mast calibrations But, of necessity, that report was focused on wind energy applications and target goals for calibration accuracy There still remained a need to make available a more general description of SODAR and other atmospheric acoustic remote sensing principles for a wider audience There is a huge body of literature available in journal papers which covers applications of acoustic remote sensing methodology in sensing atmospheric properties in the 1-km layer nearest the ground But the body of literature describing design and operating principles is much more confined and also often rather specialized Frequent requests from a range of scientists, engineers, local authorities, and other areas indicate that there is a demand for a more comprehensive collection of information on ‘how things work’ The difficulty in writing a book of this nature is to cover the principles of operation in detail sufficient enough that the reader is not left wondering about gaps in the descriptions, but at the same time trying to give a more intuitive feel for interactions between various atmospheric and instrumental components than might be found in a pedantically accurate textbook Although the resulting book does contain considerable algebra, extensive use of diagrams makes for better readability and efforts have been made to avoid the more abstruse mathematical treatments SODARs and RASS instruments are endemic in monitoring atmospheric boundary layer wind systems, turbulent transports, and thermal properties There is of xi © 2008 by Taylor & Francis Group, LLC 3588.indb 11 11/27/07 4:07:14 PM 1.5 Atmospheric Acoustic Remote Sensing WHY USE ACOUSTICS? Turbulence transports heat from higher-temperature regions to lower-temperature regions This means that turbulent patches of air have a different temperature from their surroundings, and therefore a different density and refractive index n Refractive index changes cause scattering of light, microwaves, and sound For example, turbulent scattering of starlight causes “twinkling.” But the dependence of refractive index on temperature is very much weaker for electromagnetic radiation than it is for sound (Table 1.1) Note, however, that microwave radiation may also be refracted by humidity gradients Sound therefore reflects more strongly from turbulence The generally lower cost of acoustic equipment makes sensing of atmospheric turbulence by sound even more attractive How large are the temperature variations in a turbulent patch? As discussed later, SODARs reflect efficiently from patches having diameters of half an acoustic wavelength, say 0.1 m Even if a patch had the full background temperature variation (0.01 C/m) across it, this would mean a temperature variation of only 10 –3 C and a refractive index variation of order one part in 106 1.6 DIRECT SOUND PROPAGATION FROM A SOURCE TO A RECEIVER The SODAR and RASS instruments record energy scattered back from the atmosphere An alternative remote-sensing methodology is to use direct sound transmission and to either monitor the intensity at a receiver, or monitor the travel time of the sound from the transmitter to the receiver The former technique is really a part of the study of outdoor sound propagation and has not been very much used as a remote-sensing method, partly because of continuing disagreement between observations and models New methods of signal coding and analysis may well make this a viable tool in the near future The second method is acoustic travel-time tomography and has successfully been used to study turbulence and coherent structures moving across pastures The limitation of both these direct methods is that they essentially measure in the horizontal, and vertical profiles are not easily obtained For example, an approximate guide to the height reached by sound energy which is directly measured in a horizontal propagation path is one-tenth of the horizontal range This would mean a horizontal spacing of km between the source and the receiver if refraction effects TABLE 1.1 The sensitivity of electromagnetic and acoustic remote-sensing instruments to temperature variations Refractive index variation with temperature RADAR SODAR 1.3 × 10 –6 per °C 1.7 × 10 –3 per °C © 2008 by Taylor & Francis Group, LLC 3588_C001.indd 11/20/07 5:16:43 PM What Is Atmospheric Acoustic Remote Sensing? were going to be used to sense atmospheric properties to a height of 100 m Above these sorts of distances, the ground effects can be troublesome In the case of traveltime tomography, refraction effects are undesirable, and this puts a limit on the likely horizontal range 1.7 ACOUSTIC TARGETS What are the reflectors when sound is sent vertically? Reflections of sound occur only if there is a change of density or air velocity, known as a change in acoustic refractive index The air does generally change its density and wind speed slowly with height, but this type of continuous gradient is not sufficient to give measurable reflections In practice, it is only when many reflections from small fluctuations add together that acoustic scattering can be measured As we will see later, this is a calculable effect, and relates quite directly to the turbulent state of the atmosphere It should be noted that birds, insects, and precipitation within the acoustic beam can also act as reflectors The occasional signal “spike” from a bird can readily be detected and removed by software filters, but precipitation is much more troublesome Similarly, sound leaking from the instrument sideways and reflecting off a hard structure such as a building can swamp a valid reflection from turbulence For these reasons, good understanding of the acoustic design of a SODAR’s antenna is required Antenna designs vary considerably, as seen from Figure 1.1 to 1.3 1.8 CREATING OUR OWN TARGET The principle of the RASS is to create the refractive index fluctuations deliberately and systematically by transmitting an acoustic beam vertically which is “tuned” so as to give strong reflections of the RADAR signal This has the advantage that the FIGURE 1.1 (See color insert following page 10) An experimental SODAR installed in 2004 at the British Antarctic Survey base at Halley in the Antarctic © 2008 by Taylor & Francis Group, LLC 3588_C001.indd 11/20/07 5:16:44 PM Atmospheric Acoustic Remote Sensing FIGURE 1.2 (See color insert following page 10) An AeroVironment (now Atmospheric Systems) SODAR conducting measurements of valley flows high in the Southern Alps of New Zealand FIGURE 1.3 (See color insert following page 10) Scintec’s modern SFAS mini-SODAR antenna (left-hand photograph) and a Metek SODAR–RASS (right-hand photograph) turbulent strength in the atmosphere is immaterial, and a signal is always received The method has also been transferred to RADAR wind-profilers, with both the acoustic and RADAR beams transmitted at several angles to the vertical so as to sense various components of the wind 1.9 MODERN ACOUSTIC REMOTE SENSING SODARs and RASS now have a long pedigree as operational and research instruments They are sufficiently compact to be carried in a small 4-wheel drive vehicle, and can generally be installed in a remote site within a few hours Routine operation thereafter is really only a matter of periodically checking data quality in case there has been a change caused, for example, by a power failure, degradation of one or more acoustic transducers, or some physical misalignment occurring © 2008 by Taylor & Francis Group, LLC 3588_C001.indd 11/20/07 5:16:45 PM What Is Atmospheric Acoustic Remote Sensing? Height (m) 800 400 40 12 Local Time 24 10 14 18°C FIGURE 1.4 (See color insert following page 10) The atmospheric temperature recorded during one day by the Metek DSDPA90.64 SODAR–RASS Height (m) 800 400 40 12 Local Time 24 10 ms–1 FIGURE 1.5 (See color insert following page 10) Wind speed profiles recorded during one day by the Metek DSDPA 90.64 SODAR The quality of data available is now very high For example, Figures 1.4 and 1.5 show routine plots from the Metek SODAR–RASS of temperature and wind speed Many other parameters can also be displayed Similarly, Figure 1.6 shows a plot of wind vectors recorded by an AeroVironment 4000 SODAR during a three-hour period Accuracy, with some care, can be better than 1% of wind speed, as shown in Figure 1.7 1.10 APPLICATIONS Applications are in all those areas where wind, turbulence, and temperature information is required Figure 1.8 gives some indication © 2008 by Taylor & Francis Group, LLC 3588_C001.indd 11/20/07 5:16:49 PM Atmospheric Acoustic Remote Sensing Height (m) 500 m 0m 00:00 03:00 Local Time (hours) FIGURE 1.6 Wind vectors recorded by the AeroVironment 4000 during three hours A strong upwardly propagating structure is observed 20 18 SODAR Wind Speed (m/s) 16 14 12 10 0 10 12 14 Mast Wind Speed (m/s) 16 18 20 FIGURE 1.7 Correlation between SODAR measured wind speed and wind speed measured with cup anemometers on a mast 1.11 WHERE TO FROM HERE? Over the past few years, the challenges presented to atmospheric acoustic remote sensing include greater accuracy of wind measurements for wind energy applications, © 2008 by Taylor & Francis Group, LLC 3588_C001.indd 11/20/07 5:16:52 PM What Is Atmospheric Acoustic Remote Sensing? Hazards Pollution Complex terrain Forests Transport FIGURE 1.8 Industry Urban Wind energy Some of the application areas for atmospheric acoustic remote sensing operation in urban areas, without disturbing the populace, demand for better data availability, easier installation and operation by non-experts, reduction in the need for filters to exclude rain and spurious echoes from SODARs, and desire for a more “turn-key” autonomous operation The route to meeting most of these challenges is in better design, and particularly acoustic design For example, the new AQ500 SODAR has a parabolic dish design which is innovative, coupled with better acoustic shielding than has been seen in most other systems The time is ripe for a quantum leap forward: this could be achieved through much more tightly specified acoustics, but could also come from new signal coding methodologies and from moving to a different acoustic frequency regime than used previously Given the often less-than-optimum use of these instruments, and the need for progressing toward new designs, the main scope of this book is to concentrate on describing the principles of design and operation of SODAR and RASS This is the area in which it is more difficult to find research papers There are many excellent reference sources for research applications, such as Asimakopoulos et al (1996), Coulter and Kallistratova (2004), Kirtzel et al (2001), Engelbart and Steinhagen (2001), Kallistratova and Coulter (2004), Neff and Coulter (1986), Peters and Fischer (2002), Peters and Kirtzel (1994), Seibert et al (2000), and Singal (1997) REFERENCES Asimakopoulos DN, Helmis CG et al (1996) Mini acoustic sounding — a powerful tool for ABL applications: recent advances and applications of acoustic mini-SODARs Boundary Layer Meteorol 81(1): 49–61 Beran DW, Little CG et al (1971) Acoustic Doppler measurements of vertical velocities in the atmosphere Nature 230: 160–162 Coulter RL, Kallistratova MA (2004) Two decades of progress in SODAR techniques: a review of 11 ISARS proceedings Meteorol Atmos Phys 85: 3–19 Engelbart DAM, Steinhagen H (2001) Ground-based remote sensing of atmospheric parameters using integrated profiling stations Phys Chem Earth Part B Hydrol Oceans Atmos 26(3): 219–223 Kallistratova MA, Coulter RL (2004) Application of SODARs in the study and monitoring of the environment Meteorol Atmos Phys 85: 21–37 © 2008 by Taylor & Francis Group, LLC 3588_C001.indd 11/20/07 5:17:37 PM 10 Atmospheric Acoustic Remote Sensing Kirtzel HJ, Voelz E et al (2000) RASS — a new remote-sensing system for the surveillance of meteorological dispersion Kerntechnik 65(4): 144–151 McAllister LG (1968) Acoustic sounding of the lower troposphere J Atmos Terr Phys 30 1439–1440 Moulsley TJ, Cole RS (1979) High frequency atmospheric acoustic sounders Atmos Environ 13: 347–350 Neff WD, Coulter RL (1986) Acoustic remote sensing: probing the atmospheric boundary layer D H Lenschow, pp 201–239 North EM, Peterson AM et al (1973) A remote-sensing system for measuring low-level temperature profiles Bull Am Meteor Soc 54: 912–919 Peters G, Fischer B (2002) Parameterization of wind and turbulence profiles in the atmospheric boundary layer based on SODAR and sonic measurements Meteorol Z 11(4): 255–266 Peters G, Kirtzel HJ (1994) Complementary wind sensing techniques: SODAR and RASS Ann Geophys 12 506–517 Seibert P, Beyrich F et al (2000) Review and intercomparison of operational methods for the determination of the mixing height Atmos Environ 34(7): 1001–1027 Singal SP (1997) Acoustic remote-sensing applications Springer-Verlag, Berlin, 405 pp © 2008 by Taylor & Francis Group, LLC 3588_C001.indd 10 11/20/07 5:17:38 PM Atmospheric Acoustic Remote Sensing  figure 1.1  An experimental SODAR installed in 2004 at the British Antarctic Survey base at Halley in the Antarctic figure 1.  An AeroVironment (now Atmospheric Systems) SODAR conducting measurements of valley fiows high in the Southern Alps of New Zealand © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:40:38 PM  Atmospheric Acoustic Remote Sensing figure 1.4  The atmospheric temperature recorded during one day by the Metek DSDPA SODAR–RASS figure 1.5  Wind speed proflles recorded during one day by the Metek DSDPA SODAR © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:40:46 PM 1   Atmospheric Acoustic Remote Sensing  figure 4.14  The beam pattern from an 8 × 8 square array without an applied phase gradient and with kd = Figure 4.5  The beam pattern from an × square array with an applied phase increment of π/2 per speaker and with kd = © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:40:48 PM  Atmospheric Acoustic Remote Sensing figure 4.16  The beam pattern from an 8 × 8 square array without an applied phase gradient and with kd = and a cosine-shaded speaker gain pattern 1   Figure 4.7  The beam pattern from an × square array with an applied phase increment of π/2 per speaker and with kd = and a cosine-shaded speaker gain pattern © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:40:50 PM Atmospheric Acoustic Remote Sensing  figure 4.3  Unshaded bistatic system sensitivity for baseline D = 50 m, and with preset intersection height z0 = 50 m (left) and 100 m (right) figure 4.4  Shaded bistatic system sensitivity for baseline D = 50 m, and with preset intersection height z0 = 50 m (left) and 100 m (right) © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:41:01 PM  Atmospheric Acoustic Remote Sensing FIGURE 5.28  Percentage of relative data yield of Scintec SODAR receptions, plotted against height z of the SODAR range gates and against the Richardson number Ri based on meteorological mast measurements at 100 m The solid yellow and blue lines are two con2 tours of constant CT / Z FIGURE 5.30  Data availability for the Metek SODAR based on Monin-Obhukov length L estimated from a sonic anemometer at 20 m height © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:41:06 PM Atmospheric Acoustic Remote Sensing  FIGURE 5.31  Data availability for the Metek SODAR based on Monin-Obhukov length L estimated from a sonic anemometer at 100 m height © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:41:07 PM Atmospheric Acoustic Remote Sensing FIGURE 8.6  Plots of time variations measured by the four SODARs of the C T fleld FIGURE 8.7  Matrix of covariances between C T values measured by each pair of SODARs at each height © 2008 by Taylor & Francis Group, LLC 3588_Color_Insert.indd 11/26/07 1:41:12 PM ... 34(7): 10 01? ? ?10 27 Singal SP (19 97) Acoustic remote- sensing applications Springer-Verlag, Berlin, 405 pp © 2008 by Taylor & Francis Group, LLC 3588_C0 01. indd 10 11 /20/07 5 :17 :38 PM Atmospheric Acoustic. .. Combinations 10 5 5 .1. 1 Speakers and Microphones 10 5 5 .1. 2 Horns 10 8 5 .1. 3 Phased-Array Frequency Range 10 9 5 .1. 4 Dish Design 11 0 5 .1. 5 Designing for... Group, LLC 3588_C0 01. indd 11 /20/07 5 :16 :43 PM 1. 5 Atmospheric Acoustic Remote Sensing WHY USE ACOUSTICS? Turbulence transports heat from higher-temperature regions to lower-temperature regions