简介:Startingfromnonlinearequationsonthef-planecontainingfrictionaldissipationundertheBoussinesqapproximation,anewkindofgeneralizedenergyisproposedastheLyapunovfunction,andaveragesaretakenasanyfunctionsof(x,z)insteadofthecommonly-usedmeansofbilinearfunctionsof(x,z),therebyresultinginanewcriterionofgeneralizednonlinearsymmetricstability.Itshowsthatnotonlymustthedissipativecoefficientbegreaterthanacertaincriticalvaluebuttheinitialdisturbanceamplitudemustbesynchronouslysmallerthananothermarginalvalueaswell.Itfollowsthatthelatterimposesacrucialconstraintontheformer,thusleadingtothefactthatwhentheamplitudeisbiggercomparedtoanothercriticalvalue,generalizednonlinearsubcriticalsymmetricalinstabilitymayoccur.Thenewcriterioncontributesgreatlytotheimprovementofthepreviousresultsofitskind.
简介:Inthispaper,usingHolland’smethod,theeffectofthehorizontalstructureoftropicalcyclonesontheirmotionisinvestigated.The"characteristicradius",r0characterizedasthehorizontalstructureofatropicalcyclone,inwhichmandparetheparametersofthevortex,hasbeenfoundbytheauthor.Andthenithasbeenshownthatthereisbutone"characteristicradius"foreachcyclonewithhorizontalstructure.Twodirectanalyticsolutionsfortheuniformandnon-uniformbasicflowsinsteadysituationsarepresentedwithrcResultsshowthatthechangeinthehorizontalstructureofthetropicalcycloneitselfwillhaveobviouseffectonthecyclonemotion,onbothitsdirectionandspeed.Thereforeitmustbeconsideredintheresearchonthetropicalcyclonemotion.
简介:Threenumericalexperimentshavebeencarriedoutbyusingaspectralbarotropicprimitiveequationmo-del.Itisfoundthattheresultsobtainedarequitesimilartothosewiththebarotropicfilteredmodel.Themainresultsreadasfollows:(1)Inthecasewithsymmetricorographyorwithoutorography,ifthemotionissymmetric(withre-specttotheequator,thesameistruehereafter)attheinitialinstant,thenitwouldbesymmetricafterwards.(2)Theantisymmetricorographydistributioncouldcauseantisymmetricmotion,andtheoriginalsym-metricmotionmightbecomeasymmetric.Inordertoexplaintheaboveresults,ithasbeenprovedthattheyaretheoreticallyvalid.Anditisfoundthatifthemotionisantisymmetricattheinitialinstant,thenitwouldbecomeasymmetric.Therefore,nopureantisymmetricmotioncouldbemaintained.