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Radar Meteorology Radarisakeyinstrumentusedinmeteorologyformonitoringwindandprecipitation,and hasbecome theprimarytoolusedforshort-termweatherforecasting. Thispractical text- book introduces the fundamental concepts behind radar measurements and their meteor- ologicalinterpretation. The first part of the book provides the essential background theory behind radar measurements to guide students and practitioners in the proper interpretation of radar reflectivity,Dopplervelocity,anddual-polarizationimagery.Operationalapplicationsare thenexplored,suchashowradarimagerycanbeusedtoanalyzeandforecastconvective andwidespreadweathersystems.Thebookconcludeswithanoverviewofcurrentresearch topics,includingthestudyofcloudsandprecipitationusingground-basedandspaceborne radars,signalprocessing,anddataassimilation. Numerousfull-colorillustrationsareincluded,aswellascasestudies,andavarietyof supplementary electronic material, including problem sets and animated time sequences ofimagestohelpconveycomplexconcepts.Thisbookisavaluableresourceforadvanced undergraduateandgraduatestudentsinradarmeteorologyandotherrelatedcourses,such as precipitation microphysics and dynamics. It will also make a useful reference for researchers,professionalmeteorologists,andhydrologists. FrédéricFabryisanAssociateProfessoratMcGillUniversityinMontreal,Canada,wherehe teaches topics in radar, meteorology, and the environment. He is also the Director of the MarshallRadarObservatoryatMcGill.Hisresearchcoversvariousfacetsofradarmeteor- ology,fromtechnicalaspectssuchassignalprocessingtoapplicationsofradarinhydrology andinnumericalweathermodeling,includingmoretraditionalradarmeteorologyresearch suchasthecharacterizationofthemeltinglayerofprecipitation.Hewasawardedthe2004 CanadianMeteorologicalandOceanographicSocietyPresidentPrizeforthedevelopment ofatechniquetoestimatetherefractiveindexofairusinggroundtargets. Radar Meteorology Principles and Practice FRÉDÉRIC FABRY McGillUniversity UniversityPrintingHouse,CambridgeCB28BS,UnitedKingdom CambridgeUniversityPressispartoftheUniversityofCambridge. ItfurtherstheUniversity’smissionbydisseminatingknowledgeinthepursuitof education,learningandresearchatthehighestinternationallevelsofexcellence. www.cambridge.org Informationonthistitle:www.cambridge.org/9781107070462 ©FrédéricFabry2015 Thispublicationisincopyright.Subjecttostatutoryexception andtotheprovisionsofrelevantcollectivelicensingagreements, noreproductionofanypartmaytakeplacewithoutthewritten permissionofCambridgeUniversityPress. Firstpublished2015 PrintedintheUnitedKingdombyBellandBainLtd AcataloguerecordforthispublicationisavailablefromtheBritishLibrary LibraryofCongressCataloguinginPublicationdata Fabry,Frédéric,1967– Radarmeteorology:principlesandpractice/FredericFabry,McGillUniversity. pages cm Includesbibliographicalreferencesandindex. ISBN978-1-107-07046-2 1. Radarmeteorology. 2. Radar. 3. Meteorology. I. Title. QC973.5.F33 2015 551.63053–dc23 2015008279 ISBN978-1-107-07046-2Hardback Additionalresourcesforthispublicationatwww.cambridge.org/fabry CambridgeUniversityPresshasnoresponsibilityforthepersistenceoraccuracyof URLsforexternalorthird-partyinternetwebsitesreferredtointhispublication, anddoesnotguaranteethatanycontentonsuchwebsitesis,orwillremain, accurateorappropriate. ToNicole,Roland,andVéronique Contents Preface pagexi Notation xiii 1 Meteorologyandradar 1 1.1 Howitallstarted 1 1.2 Whyradarsnow 2 1.3 Understandingradarobservations 4 1.4 Supplementalreadings 7 2 Fundamentalsofweatherradarmeasurements 8 2.1 Radar:anactiveremotesensor 8 2.2 Microwavesandtheatmosphere 9 2.3 Propagationintheatmosphere 20 2.4 Basicradarmeasurements 24 2.5 Weathersurveillance 29 3 Radarreflectivityandproducts 32 3.1 Theradarequation 32 3.2 Theequivalentreflectivityfactor 33 3.3 Reflectivityfactorandrainrate 35 3.4 Radarproducts 38 4 Reflectivitypatterns 43 4.1 Typesoftargets 43 4.2 Precipitationprocesses:aquickoverview 43 4.3 Theverticalstructureofrainechoes 45 4.4 Radarsignaturesofwidespreadrain 48 4.5 Frozenprecipitation 52 4.6 Nonprecipitationweathertargets 55 4.7 Nonweathertargets 58 4.8 Anechoidentificationapproach 61 5 Dopplervelocityinformation 65 5.1 Dopplermeasurements 65 5.2 Informationatverticalincidenceandprofiling 66 vii viii Contents 5.3 MeanDopplervelocityonPPIdisplays 76 5.4 Velocity-basedproducts 83 5.5 Datacontaminationandambiguities 86 6 Theaddedvalueofdualpolarization 92 6.1 Whypolarizationmatters 92 6.2 Dual-polarizationmeasurables 93 6.3 Signaturesandartifacts 102 6.4 Applications 110 7 Convectivestormsurveillance 115 7.1 Aforecastapproach 115 7.2 Severeconvectionanditscontrols 116 7.3 Whattolookfor 126 8 Monitoringwidespreadsystems 133 8.1 Radar,widespreadsystems,andthreatforecasting 133 8.2 Whatradarcancontribute 136 8.3 Acasestudyofwinterstormforecasting 142 8.4 Whatabouttropicalcyclones? 145 9 Radarestimationofprecipitation 148 9.1 Precipitationmonitoringneeds 148 9.2 Sourcesofestimationerrors 150 9.3 Radar-basedaccumulationgeneration 152 9.4 Uses 165 10 Nowcasting 166 10.1 Nowcastingneedsandapproaches 166 10.2 Thebasisforsimplenowcastingsystems:extrapolation 168 10.3 Precipitationnowcasting 169 10.4 Severeweathernowcasting 171 10.5 Mesoscalemodelingafterradardataassimilation 174 11 Additionalradarmeasurementsandretrievals 180 11.1 Usingmultipleviewingangles 180 11.2 MultipleDopplerretrievals 183 11.3 Near-surfacerefractiveindex 185 11.4 Multiple-frequencyandattenuationmeasurements 186 12 Cloudandspaceborneradars 189 12.1 Cloudradars 189 12.2 Spaceborneradars 195