简介：Withdailyprecipitationrecordsat586stationsinChinafor1960-2004,thisstudyinvestigatesthespatio-temporalvariationofthenumberofextremewetdays(NEWD)foreachseasoninChinaanditsrelationshipwithSSTanomaliesandassociatedatmosphericcirculationanomalypatterns,inwhichathresholdofextremeprecipitationforaseasonandastationisdefinedasthevalueofthe90thpercentilewhentheprecipitationrecordsforwetdaysduringtheseasonarerankedinanincreasingorder.ResultsshowthattherearesignificantincreasesoftheNEWDalongtheYangtzeRivervalleyduringwinterandsummer,inNorthChinaduringwinter,inSouthChinaduringspring,inNortheastChinaduringwinterandspring,andinNorthwestChinathroughouttheseasons,whilethereisaremarkabledecreaseinNorthChinaduringsummer.Besidesthelineartrend,theNEWDalsoexhibitsconsiderableinterannualandinterdecadalvariabilities.Aftereliminatingthelineartrend,theNEWDanomaliesshowdistinctseasonalpatterns.TheNEWDanomaliesarecharacterizedbya"dipole"modewithoppositephasesbetweennorthernandsouthernChinainspringandautumn,a"tri-pole"modewithoppositephasesbetweenYangtzeRivervalleyandsouthernandnorthernChinainsummer,anda"monopole"modewiththesamephaseovermostofChinainwinter.TherelationshipoftheNEWDanomaliesinChinawiththeSSTanomaliesinIndianandPacificOceansisfoundtobemainlydependentontheENSO,andassociatedatmosphericcirculationanomalypatternsfortheENSO’simpactontheNEWDinChinaareidentified.

简介：Byusingthedatasetoflightraindaysandlowcloudcoverat51stationsinSouthChina(SC),andthemethodoflinearregressionandcorrelativeanalysis,weanalyzethespatiotemporalcharacteristicsofthelightraindaysandlowcloudcoverincludingannualvariationandlong-termseasonalchange.Theresultsareasfollows:(1)ThetrendsoflightraindaysandlowcloudcoveroverSCareopposite(lightraindaystendedtodecreaseandlowcloudcovertendedtoincreaseinthepast46years).Thevaluedistributedineastishigherthanthatinwest,andcoastalareahigherthaninlandarea.(2)Theregressioncoefficientsoflightraindaysandlowcloudcoverduring1960-2005are4.88d/10yearsand1.14%/10yearsrespectively,whichhadallpassedthe0.001significancelevel.(3)Variationsoflightraindaysarerelativelysmallinspringandsummer,buttheircontributionsarelargerforannualvaluethanthatofautumnandwinter.(4)Therearetworegionswithlargevaluesofaerosolopticaldepth(AOD),whichdistributeincentralandsouthernGuangxiandPearlRiverDelta(PRD)ofGuangdong,andthevalueofAODinPRDisupto0.7.Theaerosolindexdistributedincoastalareaishigherthanintheinlandarea,whichissimilartothelightraindaysandlowcloudcoveroverSC.AerosolindexesinSCkeptincreasingwithfluctuationduringthepast27years.TheGDPofthethreeprovincesinSCincreasedobviouslyduringthepast28years,especiallyinGuangdong,whichexhibitedthatthereissimultaneouscorrelationbetweenlightraindayswiththevariablesoflowcloudcoverandreleaseofaerosolsoverSCduring1960to2005.

简介：ThisstudycomparestheimpactsofinterannualArcticseaicelossandENSOeventsonwinterhazedaysinmainlandChinathroughobservationalanalysesandAGCMsensitivityexperiments.Theresultssuggestthat(1)Arcticseaicelossfavorsanincreaseinhazedaysincentral–easternChina;(2)theimpactofENSOisoverallcontainedwithinsouthernChina,withincreased(reduced)hazedaysduringLaNi?a(ElNi?o)winters;and(3)theimpactsfromseaicelossandENSOarelinearlyadditive.Mechanistically,Arcticseaicelosscausesquasi-barotropicpositiveheightanomaliesovertheregionfromnorthernEuropetotheUralMountains(Uralsinbrief)andweakandnegativeheightanomaliesovertheregionfromcentralAsiatonortheasternAsia.TheformerfavorsintensifiedfrequencyoftheblockingovertheregionsfromnorthernEuropetotheUrals,whereasthelatterfavorsanevenairpressuredistributionoverSiberia,Mongolia,andEastAsia.Thislarge-scalecirculationpatternfavorsmorefrequentoccurrenceofcalmandsteadyweatherinnorthernChinaand,asaconsequence,increasedoccurrenceofhazedays.Incomparison,LaNi?a(ElNi?o)exertsitsinfluencealongatropicalpathwaybyinducingacyclonic(anticyclonic)lower-troposphericatmosphericcirculationresponseoverthesubtropicalnorthwesternPacific.Thenortheasterly(southwesterly)anomalyatthenorthwesternrearofthecyclone(anticyclone)causesreduced(intensified)rainfalloversoutheasternChina,whichfavorsincreased(reduced)occurrenceofhazedaysthroughtherain-washingeffect.