Radar Meteorology

Robert M. Rauber, Professor of Atmospheric Sciences, University of Illinois, Urbana-Champaign, USA.Stephen W. Nesbitt, Professor of Atmospheric Sciences, University of Illinois, Urbana-Champaign, USA.

• Preface xxiAcknowledgments xxiiiAbout the Companion Website xvii1 Properties of Electromagnetic Waves 11.1 Introduction 11.2 Electric and magnetic fields 21.2.1 The electric field 21.2.2 The magnetic field 41.2.3 Relating the electric and magnetic fields—a simple dipole antenna 51.2.4 Maxwell equations 61.3 The nature of electromagnetic radiation 81.3.1 The electromagnetic spectrum 81.3.2 Electromagnetic wave interactions 91.4 Interactions of electromagnetic waves with matter 111.4.1 Refraction 121.4.2 Reflection 121.4.3 Mie scattering 141.4.4 Bragg scattering 171.4.5 Absorption 181.5 Polarization of electromagnetic waves 18Important terms 20Review questions 21Challenge problems 222 Radar Hardware 232.1 Introduction 232.2 Frequency and wavelength 232.3 Components of a weather radar system 252.3.1 Transmitter section 262.3.2 Waveguides, rotary joints, polarization switching devices, and circulators 282.3.3 The antenna section 322.3.4 The receiver section 362.3.5 Magnetron transmitters 382.4 Specialized radar systems 402.4.1 Phased-array radars 402.4.2 Mobile and deployable radars 412.4.3 Airborne radars 432.4.4 Spaceborne radars 44Important terms 46Review questions 47Challenge problems 473 Radar Characteristics 493.1 Introduction 493.2 Range and range ambiguity 503.3 The transmitted and received signal 533.3.1 Pulse duration and pulse length 543.3.2 Power and the duty cycle 543.4 Radar geometry and types of displays 563.4.1 Common radar displays in spherical coordinates 56Important terms 64Review questions 64Challenge problems 654 The Path of a Radar Ray 664.1 Introduction 664.2 Ray propagation in an idealized atmosphere 674.2.1 Factors influencing radar ray paths 674.2.2 The path of a ray in an idealized atmosphere 694.2.3 The range and height of a pulse volume in space 724.3 Anomalous propagation 74Important terms 78Review questions 79Challenge problems 805 Power and the Radar Reflectivity Factor 825.1 Introduction 825.2 Radar equation for a solitary target 835.2.1 Power flux density incident on a target 835.2.2 Power flux density scattered back to the radar 855.2.3 Backscattered power collected by the radar antenna 865.2.4 Implications of the radar equation 875.3 Radar equation for a distributed target 895.3.1 The contributing volume for distributed targets 895.3.2 The radar cross section of distributed targets 915.3.3 The radar equation for a distributed target 945.4 The weather radar equation 955.4.1 Radar cross section of a small dielectric sphere 955.4.2 The radar reflectivity factor 965.4.3 The weather radar equation 975.4.4 The validity of the Rayleigh approximation 985.5 Summary 100Important terms 101Review questions 101Challenge problems 1026 Radial Velocity—The Doppler Effect 1046.1 Introduction 1046.2 Measurement of radial velocity 1066.2.1 Phase measurements and radial velocity retrieval 1076.2.2 Velocity ambiguities and their resolution 1086.3 Doppler spectra 1156.3.1 Doppler spectra of weather and other targets 1166.3.2 Moments of the Doppler spectrum 1176.4 Measurement of the Doppler moments 1196.5 Summary 122Important terms 123Review questions 123Challenge problems 1247 Dual-Polarization Radar 1267.1 Introduction 1267.2 The physical bases for radar polarimetry 1277.3 Measuring polarimetric quantities 1307.4 Reflectivity, differential reflectivity, and linear depolarization ratio 1327.4.1 Reflectivity factor in the dual-polarization framework (Z HH and Z VV) 1327.4.2 Differential reflectivity (Z DR) 1337.4.3 Raindrop shapes and sizes 1347.4.4 Z DR measurements in rain 1387.4.5 Z DR measurements in ice and mixed-phase precipitation 1417.4.6 Linear depolarization ratio (L DR) 1457.5 Polarization and phase 1497.5.1 Propagation differential phase shift (φ DP) 1507.5.2 Backscatter differential phase shift (δ) 1527.5.3 Specific differential phase (K DP) 1527.5.4 Retrieval of K DP 1557.5.5 Co-polar correlation coefficient (ρ HV) 1647.5.6 Using polarimetric variables together 1687.5.7 Covariation of the polarimetric variables: an example at S- and C-band 1687.5.8 Using dual-polarization variables to discern meteorological versus non-meteorological echo and non-uniform beam filling 1707.5.9 Hydrometeor classification 172Important terms 176Review questions 181Challenge problems 1818 Clear Air Echoes 1838.1 Introduction 1838.2 Ground clutter 1848.2.1 Ground clutter characteristics 1848.2.2 Sea clutter 1858.2.3 Effects of anomalous propagation 1888.2.4 Ground clutter mitigation 1888.3 Echoes from biological sources 1918.3.1 Insect echo 1928.3.2 Birds and bats 1938.4 Debris, dust, and smoke 1958.5 Aircraft echoes and chaff 1968.6 Other non-meteorological echo sources 1988.6.1 The sun 1998.6.2 Receiver noise 1998.6.3 Radio interference 2008.7 Bragg scattering 200Important terms 203Review questions 203Challenge problems 2049 Propagation Effects: Attenuation and Refractivity 2059.1 Introduction 2059.2 Attenuation 2069.2.1 Attenuation by atmospheric gases and measurement of water vapor 2079.2.2 Attenuation by cloud droplets and measurement of liquid water content 2129.2.3 Attenuation by rain and its correction 2149.2.4 Attenuation by hail 2199.2.5 Short-wavelength radars and attenuation 2249.3 Refractivity 2259.3.1 Basic principles 2269.3.2 Measurement of the water vapor field 227Important terms 229Review questions 229Challenge problems 23010 Operational Radar Networks 23210.1 Introduction 23210.2 The WSR-88D radar network 23310.2.1 Network coverage 23310.2.2 Radar characteristics and data distribution 23410.2.3 Scanning strategies 23610.2.4 Ground clutter suppression 24010.2.5 Super resolution 24010.2.6 Additional features 24210.3 Terminal Doppler weather radars 24210.3.1 Radar characteristics and data distribution 24310.4 International operational radar networks 246Important terms 248Review questions 249Challenge problems 24911 Doppler Velocity Patterns and Single-Radar Wind Retrieval 25111.1 Introduction 25111.2 Kinematic properties of the wind field 25211.3 Doppler radial velocity patterns and the wind field 25411.3.1 Large-scale flow patterns 25511.3.2 Fronts 25711.3.3 Convective scale flow patterns 25911.4 Wind retrieval with profiling radars 26111.4.1 Wind profilers 26111.5 Velocity–azimuth display wind retrieval 26411.5.1 VAD technique 26411.5.2 Extended VAD analysis 272Important terms 275Review questions 276Challenge problems 27712 Multiple Doppler Wind Retrieval 27912.1 Introduction 27912.2 Network design and deployment 27912.2.1 Meteorological considerations 28112.2.2 Sampling limitations 28112.2.3 Siting and logistics 28312.3 Characteristics of single Doppler data 28412.3.1 Geographic location of a range gate 28412.3.2 Characteristics of raw data 28412.3.3 Ambiguities and Doppler radar data editing 28712.4 Procedures for multiple Doppler syntheses 29012.4.1 Interpolation of data from spherical to Cartesian coordinates 29012.4.2 Transformation of radial velocities to orthogonal particle motion components 29212.4.3 Calculation of vertical motion from orthogonal wind components 30212.4.4 Uncertainty in vertical motion retrievals 30412.5 Summary 306Important terms 306Review questions 307Challenge problems 30813 Precipitation Estimation with Radar 31013.1 Introduction 31013.2 Measurement of precipitation rate, total precipitation, and particle size distributions 31113.2.1 Precipitation gauges 31113.2.2 Disdrometers 31313.2.3 Optical array probes 31513.3 Nature of particle size distributions 31613.3.1 The exponential size distribution 31813.3.2 The gamma size distribution 31913.4 Radar remote sensing of precipitation 31913.4.1 Determining Z–R relationships 32213.4.2 Challenges in precipitation estimation with radar 32313.5 Precipitation estimation using dual polarization 32613.6 Winter precipitation 32913.7 Measuring precipitation from space 33013.7.1 Tropical Rainfall Measuring Mission 33213.7.2 Global Precipitation Mission 332Important terms 334Review questions 334Challenge problems 33514 Warm Season Convection 33814.1 Introduction 33814.2 Mesoscale convective systems 33914.2.1 Radar-observed life cycle of an MCS 33914.2.2 Conceptual model of an MCS as observed with a research radar 34114.2.3 Radar signatures of hazardous weather in MCSs 34314.2.4 Frontal squall lines 34514.3 Supercell thunderstorms 34914.3.1 Tornado detection 35214.3.2 Radar signatures of supercells 35414.3.3 Hail detection 35614.4 Downbursts and wind shear 358Important terms 358Review questions 359Challenge problems 35915 Extratropical Cyclones 36115.1 Introduction 36115.2 Radar approaches to monitor cyclone mesostructure 36315.3 Mesoscale structures observable with radar 36615.3.1 The comma-cloud tail 36715.3.2 The comma-cloud head 371Important terms 381Review questions 381Challenge problems 38216 Tropical Cyclones 38316.1 Introduction 38316.2 Airborne and satellite radar systems for tropical cyclone research and operations 38616.2.1 NOAA WP-3D radar systems 38616.2.2 Other airborne radars used in hurricane research 38816.2.3 Satellite radars used in hurricane research 38916.3 Tropical cyclone structure and kinematics 39016.3.1 Eyewall and eye radar structure 39516.3.2 Radar structure of principal band 39916.3.3 Other bands within the hurricane vortex 40416.4 Operational use of radar to detect tropical cyclone hazards 40516.4.1 High winds and storm surge 40516.4.2 Heavy precipitation and flooding 40716.4.3 Tornadoes 409Important terms 411Review questions 411Challenge problems 41217 Clouds and Vertical Motions 41317.1 Introduction 41317.2 Cloud radars 41417.2.1 Advantages and disadvantages of cloud radars 41517.2.2 Examples of data from cloud radars 41717.3 Application of cloud radars 42117.3.1 Determining vertical motions in clouds 42117.3.2 Determining statistical cloud properties 42417.3.3 Understanding atmospheric and storm structure 42817.3.4 Understanding global cloud properties 432Important terms 432Review questions 433Challenge problems 433Appendix A List of Variables (and Chapters) 435Appendix B Derivation of the Exact Equation for a Ray Path through a Spherically Stratified Atmosphere 441Index 443