简介：对于求解线性方程组Ax=b的一般化Jacobi(JOR)迭代法,文章提出自适应策略确定JOR方法中的参数。新的修正算法仅需系数矩阵A对称正定,改善了JOR迭代法的收敛条件。最后数值实例表明新算法的有效性。

简介：Inthisstudy,weanalyzedthedynamicalevolutionofthemajor2012–2013NorthernHemisphere(NH)stratosphericsuddenwarming(SSW)onthebasisofERA-InterimreanalysisdataprovidedbytheECMWF.Theintermittentupward-propagatingplanetarywaveactivitiesbeginninginlateNovember2012ledtoaprominentwavenumber-2disturbanceofthepolarvortexinearlyDecember2012.However,nomajorSSWoccurred.InmidDecember2012,whenthepolarvortexhadnotfullyrecovered,amixtureofpersistentwavenumber-1and-2planetarywavesledtogradualweakeningofthepolarvortexbeforethevortexspliton7January2013.EvolutionofthegeopotentialheightandEliassen-Palmfluxbetween500and5hPaindicatesthatthefrequentoccurrenceoftroposphericridgesoverNorthPacificandthewestcoastofNorthAmericacontributedtothepronouncedupwardplanetarywaveactivitiesthroughoutthetroposphereandstratosphere.AftermidJanuary2013,thewavenumber-2planetarywavesbecameenhancedagainwithinthetroposphere,withadeepenedtroughoverEastAsiaandNorthAmericaandtworidgesbetweenthetroughs.Theenhancedtroposphericplanetarywavesmaycontributetothelong-lastingsplittingofthepolarvortexinthelowerstratosphere.The2012–2013SSWshowscombinedfeaturesofbothvortexdisplacementandvortexsplitting.Therefore,theanomaliesoftroposphericcirculationandsurfacetemperatureafterthe2012–2013SSWresembleneithervortex-displacednorvortex-splitSSWs,butthecombinationofallSSWs.TheremarkabletroposphericridgeextendingfromtheBeringSeaintotheArcticOceantogetherwiththeresultingdeepenedEastAsiantroughmayplayimportantrolesinbringingcoldairfromthehighArctictocentralNorthAmericaandnorthernEurasiaatthesurface.