A comprehensive introduction to the current technology and application of radar in meteorology and atmospheric sciences
Written by leading experts in the field, Radar Meteorology, A first Course offers an introduction to meteorological radar systems and applications, with emphasis on observation and interpretation of physical processes in clouds and weather systems. This comprehensive introduction to the subject offers an overview of the quantities essential to radar meteorology including the radar reflectivity factor, and Doppler, dual-polarization, and multi-wavelength radar variables. The authors highlight wind retrieval from single and multiple Doppler radars, precipitation estimation and hydrometeorological applications, with chapters dedicated to interpretation of radar data from warm season mid-latitude severe weather, winter storms, tropical cyclones and more.
In addition, Radar Meteorology highlights research applications of this burgeoning technology, exploring dynamic applications such as space-borne and ground-based vertically pointing radar systems, and cloud, airborne and mobile radars. As meteorological radars are increasingly used professionally for weather observation, forecasting and warning, this much-needed text:
- Presents an introduction to the technical aspects and current application of radar as used in the meteorology and atmospheric sciences
- Contains full-colour illustrations that enhance the understanding of the material presented
- Examines the wide-range of meteorological applications of radar
- Includes problems at the end of each chapter as a helpful review of the contents
- Provides full instructor support with all illustrations and answers to problems available via the book’s instructor website.
Radar Meteorology offers a much-needed introductory text to the study of radar as applied to meteorology. The text was designed for a one semester course based on the authors’ own course in Radar Meteorology at the University of Illinois at Urbana-Champaign.
Table of Contents
Preface xvii
Acknowledgments xxi
About the Companion Website xxiii
1 Properties of Electromagnetic Waves 1
1.1 Introduction 1
1.2 Electric and magnetic fields 2
1.2.1 The electric field 2
1.2.2 The magnetic field 4
1.2.3 Relating the electric and magnetic fields - a simple dipole antenna 5
1.2.4 Maxwell equations 6
1.3 The nature of electromagnetic radiation 8
1.3.1 The electromagnetic spectrum 8
1.3.2 Electromagnetic wave interactions 9
1.4 Interactions of electromagnetic waves with matter 11
1.4.1 Refraction 12
1.4.2 Reflection 12
1.4.3 Mie scattering 14
1.4.4 Bragg scattering 17
1.4.5 Absorption 18
1.5 Polarization of electromagnetic waves 18
Important terms 20
Review questions 21
Challenge problems 22
2 Radar Hardware 23
2.1 Introduction 23
2.2 Frequency and wavelength 23
2.3 Components of a weather radar system 25
2.3.1 Transmitter section 26
2.3.2 Waveguides, rotary joints, polarization switching devices, and circulators 28
2.3.3 The antenna section 32
2.3.4 The receiver section 36
2.3.5 Magnetron transmitters 38
2.4 Specialized radar systems 40
2.4.1 Phased-array radars 40
2.4.2 Mobile and deployable radars 41
2.4.3 Airborne radars 43
2.4.4 Spaceborne radars 44
Important terms 46
Review questions 47
Challenge problems 47
3 Radar Characteristics 49
3.1 Introduction 49
3.2 Range and range ambiguity 50
3.3 The transmitted and received signal 53
3.3.1 Pulse duration and pulse length 54
3.3.2 Power and the duty cycle 54
3.4 Radar geometry and types of displays 56
3.4.1 Common radar displays in spherical coordinates 56
Important terms 64
Review questions 64
Challenge problems 64
4 The Path of a Radar Ray 66
4.1 Introduction 66
4.2 Ray propagation in an idealized atmosphere 67
4.2.1 Factors influencing radar ray paths 67
4.2.2 The path of a ray in an idealized atmosphere 69
4.2.3 The range and height of a pulse volume in space 72
4.3 Anomalous propagation 74
Important terms 78
Review questions 78
Challenge problems 79
5 Power and the Radar Reflectivity Factor 82
5.1 Introduction 82
5.2 Radar equation for a solitary target 83
5.2.1 Power flux density incident on a target 83
5.2.2 Power flux density scattered back to the radar 85
5.2.3 Backscattered power collected by the radar antenna 86
5.2.4 Implications of the radar equation 87
5.3 Radar equation for a distributed target 89
5.3.1 The contributing volume for distributed targets 89
5.3.2 The radar cross section of distributed targets 91
5.3.3 The radar equation for a distributed target 94
5.4 The weather radar equation 95
5.4.1 Radar cross section of a small dielectric sphere 95
5.4.2 The radar reflectivity factor 96
5.4.3 The weather radar equation 97
5.4.4 The validity of the Rayleigh approximation 98
5.5 Summary 100
Important terms 101
Review questions 101
Challenge problems 102
6 Radial Velocity - The Doppler Effect 104
6.1 Introduction 104
6.2 Measurement of radial velocity 106
6.2.1 Phase measurements and radial velocity retrieval 107
6.2.2 Velocity ambiguities and their resolution 108
6.3 Doppler spectra 115
6.3.1 Doppler spectra of weather and other targets 116
6.3.2 Moments of the Doppler spectrum 117
6.4 Measurement of the Doppler moments 119
6.5 Summary 122
Important terms 123
Review questions 123
Challenge problems 124
7 Dual-Polarization Radar 126
7.1 Introduction 126
7.2 The physical bases for radar polarimetry 127
7.3 Measuring polarimetric quantities 130
7.4 Reflectivity, differential reflectivity, and linear depolarization ratio 132
7.4.1 Reflectivity factor in the dual-polarization framework (ZHH and ZVV) 132
7.4.2 Differential reflectivity (ZDR) 133
7.4.3 Raindrop shapes and sizes 134
7.4.4 ZDR measurements in rain 138
7.4.5 ZDR measurements in ice and mixed-phase precipitation 141
7.4.6 Linear depolarization ratio (LDR) 145
7.5 Polarization and phase 149
7.5.1 Propagation differential phase shift (;;DP) 150
7.5.2 Backscatter differential phase shift (;;) 152
7.5.3 Specific differential phase (KDP) 152
7.5.4 Retrieval of KDP 155
7.5.5 Co-polar correlation coefficient (;;HV) 162
7.5.6 Using polarimetric variables together 168
7.5.7 Covariation of the polarimetric variables: an example at Sand C-band 168
7.5.8 Using dual-polarization variables to discern meteorological versus non-meteorological echo and non-uniform beam filling 170
7.5.9 Hydrometeor classification 172
Important terms 176
Review questions 181
Challenge problems 181
8 Clear Air Echoes 183
8.1 Introduction 183
8.2 Ground clutter 184
8.2.1 Ground clutter characteristics 184
8.2.2 Sea clutter 185
8.2.3 Effects of anomalous propagation 188
8.2.4 Ground clutter mitigation 188
8.3 Echoes from biological sources 191
8.3.1 Insect echo 192
8.3.2 Birds and bats 193
8.4 Debris, dust, and smoke 195
8.5 Aircraft echoes and chaff 196
8.6 Other non-meteorological echo sources 198
8.6.1 The sun 199
8.6.2 Receiver noise 199
8.6.3 Radio interference 200
8.7 Bragg scattering 200
Important terms 203
Review questions 203
Challenge problems 204
9 Propagation Effects: Attenuation and Refractivity 205
9.1 Introduction 205
9.2 Attenuation 206
9.2.1 Attenuation by atmospheric gases and measurement of water vapor 207
9.2.2 Attenuation by cloud droplets and measurement of liquid water content 212
9.2.3 Attenuation by rain and its correction 214
9.2.4 Attenuation by hail 219
9.2.5 Short-wavelength radars and attenuation 224
9.3 Refractivity 225
9.3.1 Basic principles 226
9.3.2 Measurement of the water vapor field 227
Important terms 229
Review questions 229
Challenge problems 230
10 Operational Radar Networks 232
10.1 Introduction 232
10.2 The WSR-88D radar network 233
10.2.1 Network coverage 233
10.2.2 Radar characteristics and data distribution 234
10.2.3 Scanning strategies 236
10.2.4 Ground clutter suppression 240
10.2.5 Super resolution 240
10.2.6 Additional features 242
10.3 Terminal Doppler weather radars 242
10.3.1 Radar characteristics and data distribution 243
10.4 International operational radar networks 246
Important terms 248
Review questions 249
Challenge problems 249
11 Doppler Velocity Patterns and Single-Radar Wind Retrieval 251
11.1 Introduction 251
11.2 Kinematic properties of the wind field 252
11.3 Doppler radial velocity patterns and the wind field 254
11.3.1 Large-scale flow patterns 255
11.3.2 Fronts 257
11.3.3 Convective scale flow patterns 259
11.4 Wind retrieval with profiling radars 261
11.4.1 Wind profilers 261
11.5 Velocity–azimuth display wind retrieval 264
11.5.1 VAD technique 264
11.5.2 Extended VAD analysis 272
Important terms 275
Review questions 276
Challenge problems 277
12 Multiple Doppler Wind Retrieval 279
12.1 Introduction 279
12.2 Network design and deployment 279
12.2.1 Meteorological considerations 281
12.2.2 Sampling limitations 281
12.2.3 Siting and logistics 283
12.3 Characteristics of single Doppler data 284
12.3.1 Geographic location of a range gate 284
12.3.2 Characteristics of raw data 284
12.3.3 Ambiguities and Doppler radar data editing 287
12.4 Procedures for multiple Doppler syntheses 290
12.4.1 Interpolation of data from spherical to Cartesian coordinates 290
12.4.2 Transformation of radial velocities to orthogonal particle motion components 292
12.4.3 Calculation of vertical motion from orthogonal wind components 302
12.4.4 Uncertainty in vertical motion retrievals 304
12.5 Summary 306
Important terms 306
Review questions 307
Challenge problems 308
13 Precipitation Estimation with Radar 310
13.1 Introduction 310
13.2 Measurement of precipitation rate, total precipitation, and particle size distributions 311
13.2.1 Precipitation gauges 311
13.2.2 Disdrometers 313
13.2.3 Optical array probes 315
13.3 Nature of particle size distributions 316
13.3.1 The exponential size distribution 318
13.3.2 The gamma size distribution 319
13.4 Radar remote sensing of precipitation 319
13.4.1 Determining Z–R relationships 322
13.4.2 Challenges in precipitation estimation with radar 323
13.5 Precipitation estimation using dual polarization 326
13.6 Winter precipitation 329
13.7 Measuring precipitation from space 330
13.7.1 Tropical Rainfall Measuring Mission 332
13.7.2 Global Precipitation Mission 332
Important terms 334
Review questions 334
Challenge problems 335
14 Warm Season Convection 338
14.1 Introduction 338
14.2 Mesoscale convective systems 339
14.2.1 Radar-observed life cycle of an MCS 339
14.2.2 Conceptual model of an MCS as observed with a research radar 341
14.2.3 Radar signatures of hazardous weather in MCSs 343
14.2.4 Frontal squall lines 345
14.3 Supercell thunderstorms 349
14.3.1 Tornado detection 352
14.3.2 Radar signatures of supercells 354
14.3.3 Hail detection 356
14.4 Downbursts and wind shear 358
Important terms 358
Challenge problems 359
15 Extratropical Cyclones 361
15.1 Introduction 361
15.2 Radar approaches to monitor cyclone mesostructure 363
15.3 Mesoscale structures observable with radar 366
15.3.1 The comma-cloud tail 367
15.3.2 The comma-cloud head 371
Important terms 381
Review questions 381
Challenge problems 382
16 Tropical Cyclones 383
16.1 Introduction 383
16.2 Airborne and satellite radar systems for tropical cyclone research and operations 386
16.2.1 NOAA WP-3D radar systems 386
16.2.2 Other airborne radars used in hurricane research 388
16.2.3 Satellite radars used in hurricane research 389
16.3 Tropical cyclone structure and kinematics 390
16.3.1 Eyewall and eye radar structure 395
16.3.2 Radar structure of principal band 399
16.3.3 Other bands within the hurricane vortex 404
16.4 Operational use of radar to detect tropical cyclone hazards 405
16.4.1 High winds and storm surge 405
16.4.2 Heavy precipitation and flooding 407
16.4.3 Tornadoes 409
Important terms 411
Review questions 411
Challenge problems 412
17 Clouds and Vertical Motions 413
17.1 Introduction 413
17.2 Cloud radars 414
17.2.1 Advantages and disadvantages of cloud radars 415
17.2.2 Examples of data from cloud radars 417
17.3 Application of cloud radars 421
17.3.1 Determining vertical motions in clouds 421
17.3.2 Determining statistical cloud properties 424
17.3.3 Understanding atmospheric and storm structure 428
17.3.4 Understanding global cloud properties 432
Important terms 432
Review questions 433
Challenge problems 433
Appendix A List of Variables (and Chapters) 435
Appendix B Derivation of the Exact Equation for a Ray Path through a
Spherically Stratified Atmosphere 441
Index 443
