外文文献word

InternationalLaboratoryforAirQualityandHealth,QueenslandUniversityofTechnology,NationalClimateCentre,AustralianBureauofMeteorology,GPOBox1289K,Melbourne,AtmosphericResearch79(2006)1–14*aGPOBox2434,Brisbane,QLD4001,AustraliabVictoria3001,AustraliaReceived12January2005;accepted22March2005AbstractGround-basedobservationsofannualrainfallandlightningincidencecollectedoverperiodsrangingfrom9to22yearsat23stationsaroundthecontinentofAustraliawereusedtocomputevaluesofdrainyieldT,definedasthemassofrainproducedperlightninggroundflash(units:kgflÀ1)overagivenareaofground.Therainyieldwasfoundtovaryconsiderablywithgeographicallocation,seasonandclimaticconditions.Ofthe23stations,5weremid-continentalandtheseshowedameanrainyieldof2.64Â108kgflÀ1incontrasttothecoastalandnear-coastalstationsthatshowedacorrespondingmeanvalueof9.91Â108kgflÀ1.Thedifferencewasstatisticallysignificantattheconfidencelevelof95%.Whenthestationswereclassifiedaccordingtoseasonalclimatezones,thewinterandwinter-dominantrainfallstationsshowedarainyieldof1.28Â109kgflÀ1whilethesummerandsummer-dominantrainfallstationsshowedasignificantlylowervalueof5.44Â108kgflÀ1.Againthedifferencewasstatisticallysignificantatthe95%confidencelevel.Everyoneofthe23stationsshowedmeanwinterrainyieldsthatweresignificantlyhigherthanthesummervalues.Thesedifferencesareattributedtosurfaceheatingwhichcontrolssuchparametersascloudbaseheightandconvectiveavailablepotentialenergyintheatmosphere.Intermsofthebehaviouroftherainyieldwithgeographical,seasonal*Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](Y.Kuleshov).0169-8095/$-seefrontmatter.CrownCopyrightD2005PublishedbyElsevierB.V.Allrightsreserved.doi:10.1016/j.atmosres.2005.03.0042E.R.Jayaratne,Y.Kuleshov/AtmosphericResearch79(2006)1–14andclimaticconditions,theAustralianobservationsareingoodagreementwithstudiesinotherpartsoftheworld.CrownCopyrightD2005PublishedbyElsevierB.V.Allrightsreserved.Keywords:Lightning;Rainfall;Groundflash;Rainyield1.IntroductionThecloseassociationbetweenrainandlightninghasbeenrecognizedsincetimeimmemorial.TheRomanphilosopherLucretiusobservedthecorrelationin58BCandconcludedthatthundercausedrainfall.RobertHookenotedarelationshipbetweengushesofrainatthegroundandoverheadlightningin1664.Morerecently,LordKelvinandFaradaybothmadereferencestothephenomenonandhypothesizedthatfallingrainmaycauselightning.However,systematicscientificstudieswerenotcarriedoutuntilthelatterhalfofthelastcentury.Battan(1965)andPiepgrassetal.(1982)relatednumbercountsofcloudtoground(CG)lightningfromnearbythunderstormstoraingaugereadingsandfoundthemtobewellcorrelated.Manystudieshavefoundtheintensityoflightningtobepositivelycorrelatedtorainfallestimatedfromradarmeasurements(Kinzer,1974;ReapandMacGorman,1989;Williamsetal.,1992;ChezeandSauvageot,1997).IntensefallsofrainassociatedwithnearbyCGlightninghavebeendocumentedbyShackford(1960),Mooreetal.(1962),Piepgrassetal.(1982)andJayaratneetal.(1995).2.RainyieldsAlthoughthereisahighpositivecorrelationbetweenrainfallandlightning,theratioofrainmasstoCGlightningflashcountoveracommonarea,withunitsofkilogramsofrainperflash,quantitativelydefinedasthebrainyieldQ,variesconsiderablewithlocation.Ingeneral,heavyrainassociatedwithmonsoonoroceanicconvectionshowrainyieldsoftheorderof109–1010kgflÀ1,whilecontinentalconvectivethunder-stormsshowmuchsmallervaluesof107–108kgflÀ1(Williamsetal.,1992;PetersenandRutledge,1998).Zipser(1994)foundthatthenumberofthunderdaysassociatedwithheavyrainintropicalmonsoonandoceanicstormregionswassignificantlylowerthanthatincontinentalrainfallregimes.Observingtheresultsofseveralstudiesatvariousgeographicallocations,PetersenandRutledge(1998)concludedthattherainyieldvariedbyafactorof10ormoreatanygivenlocationandbyafactorofupto103betweendifferentlocationsandrainfallregimes.Atthelowerend,valuesofaround5Â107kgflÀ1werefoundinthearidsouth-westernUnitedStates.Awidesectionofthemid-continentalUnitedStatesshowedremarkablystablevaluesclusterednear108kgflÀ1,asdidalandlockedstationinBotswanawithintheAfricansubcontinent.Intropicallocations,therainyieldsincreasedsystematicallyfromacontinentalvalueof4Â108kgflÀ1toamaritimevalueof1010kgflÀ1inthewesternPacificOcean.Williamsetal.(1992)identifiedtwodistinctrainfallregimesinDarwinE.R.Jayaratne,Y.Kuleshov/AtmosphericResearch79(2006)1–143incontinentalnorthernAustralia.Rainyieldsfortropicalcontinentalbreakperiodthunderstormsandtropicaloceanicthunderstormsdifferedbyalmostanorderofmagnitude,being3Â108kgflÀ1and2Â109kgflÀ1,respectively.Similarly,rainyieldsforbreakandmonsoonperiodconvectionthatoccurredoffshoreoverMelvilleandBathurstIslandsnearDarwinshowedvaluesof8Â108kgflÀ1and8Â109kgflÀ1,respectively.Williamsetal.(1992)attributedthecontrastinglightningactivityinthetwotypesofrainfallregimestodifferencesinconvectiveavailablepotentialenergy(CAPE).Manystud