简介：

简介：Duetoincreasedaerosolemissionsandunfavorableweatherconditions,severehazeeventshaveoccurredfrequentlyinChinainthelast10years.Inaddition,theinteractionbetweentheboundarylayerandtheaerosolradiativeeffectmaybeanotherimportantfactorinhazeformation.Tobetterunderstandtheeffectofthisinteraction,theaerosolradiativeeffectonaseverehazeepisodethattookplaceinDecember2013wasinvestigatedbyusingtwoWRFChemmodelsimulationswithdifferentaerosolconfigurations.Theresultsshowedthatthemaximalreductionofregionalaveragesurfaceshortwaveradiation,latentheat,andsensibleheatduringthiseventwere88,12,and37Wm~(–2),respectively.Theplanetaryboundarylayerheight,daytimetemperature,andwindspeeddroppedby276m,1°C,and0.33ms~(–1),respectively.Theventilationcoefficientdroppedby8%–24%forinthecentralandnorthwesternYangtzeRiverDelta(YRD).Theupperleveloftheatmospherewaswarmedandthelowerlevelwascooled,whichstabilizedthestratification.Inaword,thedispersionabilityoftheatmospherewasweakenedduetotheaerosolradiativefeedback.AdditionalresultsshowedthatthePM_(2.5)concentrationinthecentralandnorthwesternYRDincreasedby6–18μgm~(–3),whichislessthan15%oftheaveragePM_(2.5)concentrationduringtheseverelypollutedperiodinthisarea.TheverticalprofileshowedthatthePM_(2.5)andPM_(10)concentrationsincreasedbelow950hPa,withamaximumincreaseof7and8μgm~(–3),respectively.Concentrationsreducedbetween950and800hPa,however,withamaximumreductionof3.5and4.5μgm~(–3),respectively.Generally,theaerosolradiativeeffectaggravatedthelevelofpollution,buttheeffectwaslimited,andthishazeeventwasmainlycausedbythestagnantmeteorologicalconditions.Theinteractionbetweentheboundarylayerandtheaerosolradiativeeffectmayhavebeenlessimportantthanthelarge-scalestaticweatherconditionsfortheformation

简介：Thestudiesontheeffectofatmosphericaerosolonclimateandenvironmentarehotissuesinthecurrentcircleofinternationalscienceandtechnology.InrecentyearsthepollutionofaerosolisgettingworseandworseoverthePearlRiverDelta.Thecloudsofaerosoloccurallyearround,withheavypollutionarealocatedatthewesternsideatthemouthofPearlRiver.ThehazeweathermainlyoccursfromOctobertoAprilnextyear,resultinginvisibilitydeterioration.Fromthebeginningof1980s,visibilitydramaticallydeteriorated,obviouslyincreasinghazeweather,inwhichtherearethreebigfluctuations,showingtheperiodsofpollutionsofdust,sulphateanddust,fineparticlefromphotochemicalprocessandsulphateanddustaccompanyingwiththedevelopmentofeconomyrespectively.Thelong-termtendencyofvisibilitycausedbyfogandlightfogdoesnotshowatendencyduetohumanactivitiesoreconomicdevelopment,whichmainlyshowstheinterannualandinterdecadalvariationofclimate.ThedeteriorationofvisibilityhascloserelationtothefineparticlesoverPearlRiverDelta,withhalfofPM10overpassthelimitedvaluesetbynationalsecondgradedstandard(150μgm-3),meanwhile,allvaluesofPM2.5overpasstheday-meanlimitedvalueofAmericannationalstandard(65μgm-3),especiallyfromOctobertoJanuarynextyear,monthlymeanvaluesofPM2.5almostreachtwotimesofstandardvalue,indicatingthefineparticleconcentrationisveryhigh.TheratioofPM2.5toPM10isalsoveryhigh,reaching58%-77%,higherespeciallyindryseasonthaninrainyseason.ThusitisthefineparticlepollutioninaerosolpollutionoverthePearlRiverDelta.Comparedwiththedataof15yearsago,theratiooffineparticletoaerosolhasobviouslyincreased.

简介：Haze-to-fogtransformationduringalonglasting,lowvisibilityepisodewasexaminedusingtheobservationsfromacomprehensivefieldcampaignconductedinNanjing,Chinaduring4-9December2013.Inthisepisode,hazewastransformedintofogandthefoglastedfordozensofhours.Theimpactsofmeteorologicalfactorssuchaswind,temperature（T）andrelativehumidity（RH）onhaze,transitionandfogduringthisepisodewereinvestigated.Resultsrevealedsignificantdifferencesbetweenhazeandfogdays,duetotheirdifferentformationmechanisms.Comparisonwasmadeforboundary-layerconditionsduringhazydays,haze-to-fogdaysandfoggydays.DistributionsofwindspeedandwinddirectionaswellassynopticweatherconditionsaroundNanjinghaddeterminativeimpactsontheoccurrencesandcharacteristicsofhazeandfog.WeakenedsoutherlywindinsouthernNanjingresultedinhighconcentrationofpollutants,andhazeeventsoccurredfrequentlyduringthestudyperiod.Thewindspeedwaslessthan1ms-1inthehazeevent,whichresultedinastableatmosphericconditionandweakdispersionofthepollutants.Theheightofthetemperatureinversionwasabout400mduringtheperiod.Theinversionintensitywasweakandthetemperature-differencewas4℃km-1orlessinhaze,whiletheinversionwasstronger,andtemperature-differencewasabout6℃km-1,approachingtheinversionlayerintensityinthefogevent.HazeeventisstronglyinfluencedbyambientRH.RHvaluesincreased,whichresultedinhazedaysevidentlyincreased,suggestingthatanincreasingfractionofhazeeventsbecausedbyhygroscopicgrowthofaerosols,ratherthansimplybyhighaerosolloading.WhenRHwasabove90%,hazeaerosolsstartedtobetransformedfromhazetofog.Thisstudycallsformoreeffortstocontrolemissionstopreventhazeeventsintheregion.

简介：

简介：AcomparativestudyontheverticaldistributionsofaerosolopticalpropertiesduringhazeandfloatingdustweatherinShanghaiwasconductedbasedonthedataobtainedfromamicropulselidar.Therewasadistinctdifferenceinlayerthicknessandextinctioncoefficientunderthetwotypesofweatherconditions.Aerosolswereconcentratedbelow1kmandtheaerosolextinctioncoefficientsrangedfrom0.25to1.50km-1onhazedays.Incontrast,aerosolswithsmallerextinctioncoefficients(0.200.35km-1)accumulatedmainlyfromthesurfaceto2kmonfloatingdustdays.Theseasonalvariationsofextinctionandaerosolopticaldepth（AOD）forbothhazeandfloatingdustcasesweresimilargreatestinwinter,smallerinspring,andsmallestinautumn.Morethan85%oftheaerosolsappearedintheatmospherebelow1kmduringseverehazeandfloatingdustweather.Thediurnalvariationoftheextinctioncoefficientofhazeexhibitedabimodalshapewithtwopeaksinthemorningoratnoon,andatnightfall,respectively.Theaerosolextinctioncoefficientgraduallyincreasedthroughoutthedayduringfloatingdustweather.Casestudiesshowedthathazeaerosolsweregeneratedfromthesurfaceandthenliftedup,butfloatingdustaerosolsweretransportedverticallyfromhigheraltitudetothesurface.TheAODduringfloatingdustweatherwashigherthanthatduringhaze.Theboundarylayerwasmorestableduringhazethanduringfloatingdustweather.

简介：Long-lastingexpansionofhazepollutioninChinahasalreadypresentedasternchallengetoregionaljointpreventionandcontrol.Thereisanurgentneedtoenlargeandreconstructthecoverageofjointpreventionandcontrolofairpollutioninkeyarea.Airqualitymodelscanidentifyandquantifytheregionalcontributionofhazepollutionanditskeycomponentswiththehelpofnumericalsimulation,butitisdifficulttobeappliedtolargerspatialscaleduetothecomplexityofmodelparameters.Thetimeseriesanalysiscanrecognizetheexistenceofspatialinteractionofhazepollutionbetweencities,butithasnotyetbeenusedtofurtheridentifythespatialsourcesofhazepollutioninlargescale.Usingeconometricframeworkoftimeseriesanalysis,thispaperdevelopedanewapproachtoperformspatialsourceapportionment.WeappliedthisapproachtocalculatethecontributionfromspatialsourcesofhazepollutioninChina,usingthemonitoringdataofparticulatematter(PM2.5)across161Chinesecities.Thisapproachovercamethelimitationofnumericalsimulationthatthemodelcomplexityincreasesatexcesswiththeexpansionofsamplerange,andcouldeffectivelydealwithseverelarge-scalehazeepisodes.

简介：Chemicalcomposition,hourlycounts,andsizesofatmosphericcarbonaceousparticlesweremeasuredtoinvestigatetheirmixingstateonclearandhazydays.623,122carbonaceousparticleswithsizes0.2-2.0μmwasanalyzedusingasingle-particleaerosolmassspectrometerfrom1stto17thJanuary2013.Particletypesincludedbiomass/biofuelburningparticles(biomass),elementcarbon(EC-dominant)particlesthatwerealsomixedwithbiomass/biofuelburningspecies(EC-biomass)orsecondaryspecies(EC-secondary),organiccarbon(OC),internallymixedOCandEC(OCEC),ammonium-containing(ammonium)andsodium-containing(sodium)particles.Oncleardaysthetoprankedcarbonaceousparticletypeswerebiomass(48.2%),EC-biomass(15.7%),OCEC(11.1%),andsodium(9.6%),whileonhazydaystheywerebiomass(37.3%),EC-biomass(17.6%),EC-secondary(16.6%),andsodium(12.7%).ThefractionsofEC-secondary,ammonium(10%),andsodiumparticletypeswereelevatedonhazydays.NumbersofEC-secondaryparticlesweremorethanfourtimesthoseoncleardays(4.1%).Thus,carbonaceousparticlesmixedwithammonium,nitrateandsulfateduringagingandtransport,enhancingtheirlightextinctioneffectsandhygroscopicgrowthunderhighrelativehumidityonhazydays,furtherreducingvisibility.Ourreal-timesingle-particledatashowedthatchangestomixingstatehadasignificantimpactonlightextinctionduringhazeeventsinNanjing.

简介：ThisstudyinvestigatesthecorrelationbetweenPM10andmeteorologicalfactorssuchaswindspeed,atmosphericvisibility,dewpoint,relativehumidity,andambienttemperatureduringabrownhazeepisode.InordertoidentifythepotentialsourcesofPM10duringbrownhazeepisode,respirableparticulatematter(PM10)wascollectedduringbothnon-hazedaysandhazedaysandfurtheranalyzedformetallicelements,ionicspecies,andcarbonaceouscontents.Amongthem,ionicspeciescontributed45-64%toPM10,whilemetallicelementscontributed7-21%toPM10whichwassmallerthantheotherchemicalconstituents.TheaverageOC/ECratio(42)inhazedayswasaboutthreetimesoftheaverageOC/ECratio(14)innon-hazedays.Byusingchemicalmassbalance(CMB)receptormodel,themajorsourceswereapportioned,includingtraffics,incinerators,coalcombustion,steelindustry,petrochemicalindustry,andsecondaryaerosols,etc.ThecontributiontoPM10concentrationofeachsourcewascalculatedforallthesamplescollected.TheresultsshowedthatcoalcombustionwasthemajorsourceofPM10innon-hazedaysandsecondaryaerosolswerethemajorsourceinhazedays,followedbypetrochemicalindustry,incinerators,andtraffics,whileothersourceshadnegligibleeffect.

简介：AnupswinginhazeweatherduringautumnandwinterhasbeenobservedoverNorthandNortheastChinainrecentyears,imposingadverseimpactsuponlocalsocioeconomicdevelopmentandhumanhealth.However,suchanincreaseintheoccurrenceofhazeeventsanditsassociationwithnaturalclimatevariabilityandclimatechangearenotwellunderstood.Toinvestigatetheclimatologyofthemeteorologicalfactorsassociatedwithhazeeventsandtheirnaturalvariability,thisstudyusesameteorologicalpollutionindexcalledPLAM(ParameterLinkingAir-qualitytoMeteorologicalconditions)andERA-Interimreanalysisdata.TheresultssuggestthathighPLAMvaluestendtooccuroversouthernpartsofnorthernChina,implyingtheweatherconditionsoverthisareaarefavorablefortheoccurrenceofhazeweather.Fortheperiod1979–2014,theregionalmeanPLAMshowsanoverallincreaseacrossBeijing,Tianjin,andHebeiProvince,andpartsofShanxiProvince.Also,aperiodicityof28–34monthsisfoundinthetemporalvariationofPLAM,whichimpliesapotentialassociationofPLAMwiththestratosphericQuasi-BiannualOscillation(QBO).ByusingtheQBOindexduringtheautumnandwinterseasonsintheprecedingyear,anincreaseinPLAMisfoundforthewesterlyphasesoftheQBO,relativetotheeasterlyphases.Anupper-troposphericwarmingisalsofoundinthewesterlyphases,whichcaninduceastablestratificationthatfavorstheincreaseinPLAMacrossthemidlatitudes.Themodulationsoflarge-scaleenvironmentalfactors,includingmoiststaticstability,verticalvelocity,andtemperatureadvection,alsoacttoenhancePLAMinthewesterlyphases.However,thebaroclinictermofmoistpotentialvorticityat700hPatendstodecreaseoverthesouth,andanincreaseinlow-levelascentisfoundoverthenorth.ThesefactorscanreducePLAMandpossiblylimitthestatisticalsignificanceoftheincreasedPLAMinthewesterlyphasesoftheQBO.

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.

简介：Laser-induceddamageinfusedsilicaopticsgreatlyrestrictstheperformancesoflaserfacilities.Grayhazedamage,whichisalwaysinitiatedonceriapolishedoptics,isoneofthemostimportantdamagemorphologiesinfusedsilicaoptics.Inthispaper,thelaser-inducedgrayhazedamagesoffourfusedsilicasamplespolishedwithCeO_2,Al_2O_3,ZrO_2,andcolloidalsilicaslurriesareinvestigated.Foursamplesallpresentgrayhazedamageswithmuchdifferentdamagedensities.Then,thepolishing-inducedcontaminantandsubsurfacedamagesinfoursamplesareanalyzed.TheresultsrevealthatthegrayhazedamagescouldbeinitiatedonthesampleswithoutCecontaminantandareinclinedtoshowatightcorrelationwiththeshallowsubsurfacedamages.

简介：摘要目的探讨中低度近视眼行经上皮准分子激光角膜切削术（Trans-PRK）中使用0.02%丝裂霉素C（MMC）预防术后角膜上皮下雾状混浊（haze）的临床效果。方法回顾性队列研究。纳入行Trans-PRK的近视眼患者295例（588只眼），其中低度近视眼（近视度数<3.00 D）45例（90只眼），年龄（20.53±4.95）岁（18~41岁）；男性37例，女性8例；32只眼术中使用MMC浸润角膜基质床。中度近视眼（近视度数≥3.00 D）患者250例（498只眼），年龄（23.66±6.12）岁（18~46岁）；男性168例，女性82例；261只眼术中使用MMC。低度和中度近视眼患者术中MMC的作用时间分别为15和30 s。所有患者随访6个月，观察指标包括最佳矫正视力、等效球镜度数及haze情况。正态分布资料的比较用两独立样本t检验，非正态分布资料的比较采用Mann-Whitney U检验，术后haze的发生情况比较采用χ²检验。结果按照Fantes分级，将0.5~4级均纳入标准进行haze评估。术中使用MMC的低度近视眼患者术后haze发生率为6.25%（2/32），未使用MMC者为8.62%（5/58），且均为0.5级haze，差异无统计学意义（χ²=0.00，P>0.999）。术中使用MMC的中度近视眼患者术后haze发生率为9.19%（24/261），均为3个月内发生，其中91.67%（22/24）haze为0.5级，8.33%（2/24）haze为1级，未使用MMC者术后haze发生率为29.53%（70/237），其中84.29%（59/70）haze为3个月内发生，60.00%（42/70）haze为0.5级，18.57%（13/70）haze为1级，5.71%（4/70）haze为2级，未发生2级以上haze；15.71%（11/70）haze在3个月之后发生且均为0.5级，差异有统计学意义（χ²=12.36，P=0.002）。术后6个月，术中使用和未使用MMC的低度近视眼患者最佳矫正视力分别为5.0（5.0, 5.1）和5.0（5.0, 5.1）（Z=-0.34， P=0.733），等效球镜度数分别为（0.33±1.07）和（0.32±0.57）D（t=0.25，P=0.805），差异均无统计学意义；术中使用和未使用MMC的中度近视眼患者最佳矫正视力分别为5.0（5.0, 5.1）和5.0（5.0, 5.1）（Z=-2.05，P=0.040），等效球镜度数分别为（0.66±0.85）和（0.53±0.67）D（t=2.97， P=0.003），差异均有统计学意义。结论Trans-PRK联合0.02%MMC可以显著降低中度近视眼行术后haze的发生率和严重程度，但对于低度近视眼无明显效果。