简介：Asthestrongestsubseasonalatmosphericvariabilityduringborealwinter,threeremarkablesuddenstratosphericmajorwarming(SSW)eventsinthe2000sareinvestigatedintermsoftheBrewer–Dobsoncirculation(BDC)response.Ourstudyshowsthatthechangesofcross-isentropicvelocityduringtheSSWsarenotonlyconfinedtothepolarregion,butalsoextendtothewholeNorthernHemisphere:enhanceddescentinthepolarregion,aswellasenhancedascentinthetropics.WhentheaccelerationofthedeepbranchoftheBDCdescendstothemiddlestratosphere,itsstrengthrapidlydecreasesoveraperiodofonetotwoweeks.TheaccelerationofthedeepbranchoftheBDCisdrivenbytheenhancedplanetarywaveactivityinthemid-to-high-latitudestratosphere.DifferentfromtherapidresponseofthedeepbranchoftheBDC,tropicalupwellinginthelowerstratosphereacceleratesupto20%–40%comparedwiththeclimatology,20–30daysaftertheonsetoftheSSWs,andtheaccelerationlastsforonetothreemonths.Theenhancementoftropicalupwellingisassociatedwiththelarge-scalewave-breakinginthesubtropicsinteractingwiththemidlatitudeandtropicalQuasi-BiennialOscillation–relatedmeanflow.

简介：Using1°×1°finalanalysis(FNL)datafromtheNationalCentersforEnvironmentalPrediction(NCEP),precipitationdatafromtheTropicalRainfallMeasuringMission(TRMM)andthebest-tracktropicalcyclone(TC)datasetprovidedbytheJapanMeteorologicalAgency(JMA)forJune-Augustof2000-2009,wecomprehensivelyconsiderthetwofactorslow-levelmoisturechannelandinteractionbetweenTCsandmid-latitudesystemsandimplementastatisticalanalysisofremoteprecipitationinEastAsiatothenorthof0°andtothewestof150°E.48casesofremoteprecipitationoccurredinthisperiod,whicharecategorizedintofiveclasses.Afteracompositeanalysisofthedifferentclasses,themainsystemsat850hPaand500hPathatimpacttheremoteprecipitationareasfollows:TC,mid-latitudetrough,subtropicalhighandwatervaporchannel.Inparticular,thewatervaporchannelwhichusuallyconnectswithIndianmonsoonhasthemostsignificantimpactonremoteheavyrainfall.Anotherimportantfactoristhemid-latitudetrough.Thetypeofnorthtrough/vortex-southTCremoteprecipitationeventshappenmostfrequently,accountingfor68.8%ofthetotalincidence.MostremoteprecipitationeventsoccurontherightsideoftheTCpath(representing71%ofthetotalnumber).At200hPa,theremoteprecipitationeventsusuallyoccurontherightrearportionofahigh-altitudejetstream,andthereisananti-cyclonicvortextotheeastandwestoftheTCs.Whenthereisnoanti-cyclonicvortextotheeastoftheTC,theTCisrelativelyweak.WhentheremoteprecipitationoccurstothenorthwestoftheTCandthereisatroughinthenorthwestdirection,theTCisrelativelystrong.NumericalexperimentsarecarriedoutusingWeatherResearchandForecast(WRF)model.TheresultsshowsthattheTCplaysamainroleinproducingtheheavyprecipitationandresultsintheenhancementofprecipitationbyimpactingthewatervaporchannel.