Nov 20, 1995 - Perturbation of East Asian Continental Air Mass to Pacific. Oceanic Troposphere ... volume sampler, to a sampling line for NMHC and CO, and.
JOURNAL
OF GEOPHYSICAL
RESEARCH,
VOL. 100, NO. Dll,
PAGES 23,143-23,151, NOVEMBER
20, 1995
The 1991 PEACAMPOT aircraft observationof ozone,NOx, and SO2 over the East China Sea, the Yellow Sea, and the Sea of Japan ShiroHatakeyama,1 KentaroMurano,1HiroshiBandow, l,2 FumioSakamaki, 1 MasahikoYamato, 3 Shigeru Tanaka, 4 andHajimeAkimotol,5 Abstract. Atmospheric pollutants overnorthwest PacificRim region(theEastChina Sea,the Yellow Sea,andthe Seaof Japan)wereobserved from an airplanefrom October5 to October 11, 1991, as one of the first intensivefield studiesof the InternationalGlobal
Atmospheric Chemistry/ EastAsianNorthPacificRegionalExperiment(IGAC/APARE). Ozone,NOx, Aerosols,SO2,hydrocarbons, CO, andaldehydes weremeasured.In this paper,the resultsof thisexperiment for ozone,NOx andSO2measurements aredescribed. OzoneandNOx werenegatively correlated, whichis contraryto the normalcorrelation observed in background areas.We believethatthisis dueto the largecontribution of the upperatmosphere in mostcases.The verticaldistribution of SO2 concentrations indicates the impactof theAsiancontinentalair mass. Introduction
Human activity in the East Asian Pacific Rim region is among fl•e briskestin the world [Rodhe, 1989] and is characterizedby high and rapidly growing anthropogenic emissions of NOx, SO2 [Galloway,1989;Kato andAkimoto, 1992; Akimoto and Narita, 1994], hydrocarbons and other air pollutants. However,no intensivefield study of this area'satmospheric chemistrydirectedtowardthe elucidation of the impactof theseanthropogenic emissions ontheoceanic atmosphere has been implemented until the recent internationalinitiative of IntemationalGlobal Atmospheric Chemistry Program / East Asian North Pacific Regional Experiment(IGAC/APARE) [Pszennyand Prinn, 1994]. The main focusof the APARE activity is to studychemical processes and long-rangetransportof atmosphericspecies overthe northwestern Pacificandto estimatethe magnitude of humanimpactonthe oceanicatmosphere overthisregion. Perturbation of East Asian Continental Air Mass to Pacific
investigatethe transport and chemical transformationof gaseousspeciesover the EastAsian PacificRim regionby measuringthe spatialdistributions andtemporalvariationsof ozone, NO x, PAN, SO2, NMHC, CO, etc., and (2) to characterizeand quantify aerosolstransportedin this area. Table 1 liststhe chemicalspeciesmeasuredor sampledon the plane, responsibleinvestigators,and their respective institutions. The meteorologicalparameters,temperature, andhumiditywerealsorecorded. The
PEACAMPOT
consisted
of
both
airborne
measurementof pollutants and intensive ground-based observations. In this paper the results of the airborne measurements aredescribed.The resultsof the ground-based observations will be reportedelsewhere.
Experiments Measurements
OceanicTroposphere (PEACAMPOT) was one of the first
of Gases
The aircrat•,a Cessna404 with twin reciprocalengines (maximumpayload1300 kg, maximumvelocity306 kin/h, in APARE:PacificExploratoryMission-West (PEM-WEST) cruisingrange2880 kin, and maximumaltitude9150 m) by NASA (United States) and Climate and Air Quality was charteredfrom the ShowaAviationCompany,Japan. Taiwan Station(CATS) by Taiwan [Akimotoet al., 1995]. The Cessna404 missionsall originatedfrom Nagasaki The scientificobjectivesof the PEACAMPOT were (1) to (Ohmura)Airportwith flightsto Yoron, Seoul,and Niigata on October5-6, 7-8, and 10-11, 1991, respectively (Figure 1NationalInstitute for Environmental Studies, Tsukuba, Ibarald, 1). Flightswith samplingat both •3000 m and •460 m Japan. 2NowatUniversity of Osaka Prefecture, Sakai,Osaka, Japan. altitudeswere carried out exceptthe round-tripflight to Seoulfor whichtheflightwasconfined to a singlealtitudeof 3Gunma University, Maebashi, Gunma, Japan. about3000 m. An intercomparison with measurements by 4KeioUniversity, Kohoku-ku, Yokohama, Kanagawa, Japan. 5NowatTheUniversity of Tokyo,Meguro-lah Tokyo,Japan. the PEM-WEST DC-8 over the East China Sea was made for the returnflightfromYoronon October6. Copyright1995 by the AmericanGeophysical Union. Outsideair was introducedintothe airplanein two ways. One inlet was a 3/8-inch Teflon tube runningfrom the nose Papernumber95JD02269 0148-0227/95/95 JD-02269 $05.00 of the airplaneto a glassmanifoldlocatedin the middle of intensive field studies. There were two other studies included
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Table 1. MeasuredSpecies, Technique,andResponsible Investigators Species
Technique
Investigator
03 UV Absorption S. Hatakeyama NOx* Chemiluminescense H. Bandow NMHC Grab Sampling F. Sakamaki NI•C Grab Sampling D. Blake CO Grab Sampling D. Blake SO2 Impregnated Filter S. Tanaka AldchydesImpregnated Cartridge H. Tsuruta Aerosols Impactor M. Yamato Aerosols Tape Sampler K. Murano
Institution NIESa NIESb NIES UC Irvine UC Irvine KeioUniversity Inst.Agro-Env. GunmaUniversity NIES
NOx* meansNOx measuredwith a TECO model 42S NOx analyzer,which may containsomepartof nitricacidandorganicnitrates(seetext). a) NationalInstitutefor EnvironmentalStudies
b)NowattheUniversity of Osaka Prefecture.
the cabin. Sampleair for ozoneandNOx wastakenthrough improvedpumpingability therebyreducingpressurein the chamberand(2) the useof pureoxygen this glassmanifold. The other samplingline consistedof chemilunfinescence three stainlesssteel tubes, of 1-inch, 1/2-inch, and 1/4-inch to make ozone. In this analyzera molybdenumconverter tubing and set on the copilot'swindow. Sampleair was operating at 320øC convertednitrogen oxides to NO. introduceddirectly throughthesethree tubes to a high- Conversionefficiencyfor nitric acid and some organic butit maybe lessthanunity. volumesampler,to a samplingline for NMHC and CO, and nitrateshasnotbeenestablished, to an impregnatedfilter sampler for acidic gases and Thusthenitrogenspecies detected asNOx withthisanalyzer ammonia,respectively. includesomePartof NOy,andwill be denoted hereafter as Ozone was monitored with a TECO model 49 UV NOx*. absorption ozoneanalyzerwith 4-s switchingof thelightpath NO andNOx* weremeasured by switching thesampleair for its dual cell system. Pressureand temperaturewere flow in three modes. One was NO mode in which NO was automaticallycorrected. Calibrationwas made againsta measured without passingthe sample air through the standardozone supplier(TECO model 49PS owned by converter.Anotherwas NOx* modein whichNOx* was NationalCenterof Atmospheric Research,(NCAR)). measuredby passingsampleair throughthe converter.The Measurementsof nitrogenoxides were made with an otherwasprereactor mode. In thismode,chemiluminescence ozone-chemiluminescence NO- NOx analyzer(TECO, model from the NO + ozonereactionwas completedin an extra 42S). This commercialanalyzerwasmodifiedto improveits volume inserted before the chemiluminescencechamber, detectionlimit for the aircraft.measurements.The major givinga dynamiczeroreadingfor the analyzer.A sequence modifications were (1) the use of flow-controlled air of the three modescomprised eachset of NO and NOx* sampling with a thermal mass-flow-metersystem,which measurements and took 30 s. The 2-min runningmeans (four intermittentmeasurements for one species)reported hereas averagevalueshad a detectionlimit of 25 ppt with a S/N ratio of one. 136
140
I,•'
--
SO2 was collectedwith an alkalinefilter (Whatman41, 47 mm {) whichhad beenimpregnated with 1% (w/w) of Na2CO3 andglycerolsolution.Thealkalinefilterwassetin a two-stage filter holderwith a prefilter(Milliporemembrane filter, 47 mm {, Type AA) to eliminateparticles.The twostagefilter holder was connectedto the 1/4-inch stainless inletpipewith a Teflontubeandair waspulledthroughthe alkalinefilterwith a vacuumpump. Eightsamples for SO2 measurementsduring each observation flight were continuously collectedfor 15 or 20 min at air flow ratesof 20 - 30 L/min.
The SO2 collectedon the alkalinefilterswas extracted with distilled and deionized water with a shaker.
The
extracted samplesolutionwasfilteredwitha filterdisk(pore size,0.2 gun)andthenmadeup to 10 mL with distilledand deionizedwater. The samplesolutionwaspassedthrougha Figure 1. Flightplansof the 1991PEACAMPOTcampaign. cartridgepackedwith cationexchange resinto adjustthepH
HATAKEYAMA
ET AL.'
AIR POLLUTANTS
of the solutionto lessthan 5. After thispH adjustment,5 mL
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IO0
of samplesolutionwasinjectedontoa concentration column in an ion chromatograph.Sulfite and sulfateions in the samplesolutionswere separatedand determinedby ion chromatography. Trajectory Analysis
The basicmeteorological datausedwerethe isobaricgrid fieldsof the globalanalysispreparedby the Meteorological Agencyof Japan. The ordinaryisobaricanalysiswasmade withthe abovedataby the Meteorological Association.The analysisisproduced twicedailyat themainsynoptic timesof 0000UT and 1200UT. The grid for calculationis 1.875ø longitudex 1.875ø latitude. The levelsof analysiswere ground,1000, 850, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 30, 20, and 10 hpa. The interpolationof wind velocityon trajectorieswere made as follows: (1)vertical interpolationwas made by a linearinterpolation betweenthe wind velocityat the analysis altitudeabove and below the analyzinglevel, (2)horizontal interpolationwas made by a dual first-orderinterpolation using four grid points around each analysispoint, and (3)time interpolation of wind velocitywas performedby a linearinterpolation of the windvelocitiesof the previousand followingwind datapoints. The trajectories were pursued for 4 days. Figures8 and 10-12 showbothbackwardand forward trajectoriesstartingfrom the calculatedstarting points.
Figure 3. Mixingratiosof atmospheric pollutants andflight altitude on October6, 1991. Symbolsare the same as in Figure 2.
Japanon October11. Becauseof the typhoon,northwinds prevailedon October 7 and 8 over the Yellow Sea, and northeasterlywinds dominatedover the Sea of Japan on October 10 and 11.
Ozone and NOx*
The East C!dna Sea(October 5-6, 1991). Mixing ratios of ozoneandNOx* observed duringthe 1991PEACAMPOT campaign are shown with flight altitude and relative humidityin Figures2-7. Ozonemixingratio was generally 40-50 partsperbillionby volume(ppbv)at 3000 m altitude. Clear differencesin the altitudedependence of ozonemixing
Results
and Discussion
ratio were seen between the East China Sea and the Sea of
Japan. Over the EastChina Seathe mixingratio of ozone was higherat 460 m thanat 3000 m. On the contrary,it was A stationaryfrontlay in the EastChina Seabetweenthe higher at 3000 m thanat 460 m overtheSeaof Japan. islandof K3mshu,Japan,and Taiwan on October5 and 6. Mixing ratiosof NOx* in thefreetroposphere (at 3000 m Our airplanepassedacrossthe front on October5 on the altitude) ranged from 0.4 to 2 ppb during the campaign. The flightfromNagasakito YoronIsland. A seriesof typhoons NO mixing ratios were close to or below the detection limit approached Japanfrom September to October. Duringthe observation period(fromOctober5 to October11), Typhoon of the analyzer(25 ppt) in mostcases,exceptfor the period between 1120 and 1230 JST on October 5, 1994. Therefore Orchid (T21) approached Japanslowly, comingclosestto the mixingratiosof NO arenotshown. High mixingratios(morethan 1.2 ppb)of NOx* at 3000 m wereobserved duringbothflightsoverthe EastChina Sea General
Weather
Condition
10o
25OO
10o
aft0
2O0OE
0
•
•
a
•
0
nme(JST)
•i•re Z. Mi•in8 ratios NOx* (broadlinc), ozone(d•hcd linc), relativehumidit• pollutants andflight (•a• lincin percentunits),] O0•SO•(sho• strai•t linc,the Figure4. Mixingratiosof atmospheric •aluc showsthe a•½raScdurin8eachsamplin8period))and altitudeon October7, 1991. Symbolsare the sameas in Figure2. •)t altitu& (thinlinc,fi•)t a•is) onO•obcr 5, 1• ].
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25OO
0
Figure 5. Mixingratiosof atmospheric pollutants andflight Figure7. Mixingratiosof atmospheric pollutants andflight altitudeon October8, 1991. Symbolsare the sameas in altitudeon October11, 1991. Symbolsare the sameas in Figure2. Figure2.
(Figures2 and3). The highestmixingratiosof NOx* (3.7 ppb at 460 m and 2.3 ppb at 3000 m) were observedin the
upperatmosphere but NO is only 30% of NOx in the boundary layer. The percemage of NO observed duringthis experiment was muchlowerthanthat suggested by Ehhalt andDrumond[1988]. The reasonshouldbe thatNOx* in this studycontainedmany nitrogeneous speciesotherthan NO2. The low mixing ratio of NOx* and the higher proportion of NO in NOx* in the formerair masssuggests the impactof the upper atmosphere.Thus thesedata all indicatethattheformerair masscamefroma higheraltitude andthelatterfromtheboundarylayer. At-460 m, highmixingratiosof NOx* (average 3.3 ppb) alongwith highmixingratiosof ozone(average50.6 ppb) wereobserved.SO2 wasalsorelativelyhigh(0.36 and0.6 ppbon averagefor the samplingperiods1254-1309JST and 1309-1324 JST, respectively). Back trajectoryanalysis
latter part of the flight on October5 (Figure2). Abrupt changesin the NOx* and ozonemixingratioswere obvious around 1230 JST even though the flight altitude was constant. Meteorologicaldata for that day show that a stationaryfront lay over the area in the east-westdirection. The abruptchangein the NOx*, ozone,and SO2 mixing ratiosshouldbe dueto thedifference of thenatureor history of the air masseson either side of the front; the earlier samples(before 1230 JST) could be representative of the subsiding free tropospheric air mass,and the later samples couldbe representative of the ascending air massaffectedby anthropogenic emissions. The relativehumidityand NO data for this flight (Figure 2) are quite consistent with this explanation. Namely, the relative humidity of the air shows (Figure 8) that the air mass which reachedthe samples takenbefore1230JSTwasquitelow(lessthan5%), samplingpoint of 29ø8'N, 127ø25'Eat 460 m altitude at whilethatfor theair samples takenafter1230 JSTwashigh (around60% or higher). Significantamountsof NO were presentonly in the formerair mass. The averagemixing 60 _: .............................. :...............,•............... :............... ratioof NO between1120 and1230 JSTwas28.9 ppt(5.9% of NOx* on average).In the latterair mass,NO wasbelow the detection limit of our instrument. Ehhalt and Drumond
[1988] pointedoutthat 80% of NOx is present asNO in the 10o
•
25OO
30 ,
:
ß
.
i .
0 ,
,
Time(JST)
20
'
1O0
Figure 6. Mixing ratiosof atmospheric pollutantsandflight altitudeon October]0, ]99 ]. Symbolsare the sameas in Figure2.
110
120
130
140
150
Figure 8. Backtrajectoryof the air masssampledat 1320 JST on October5 at 29ø8?/, 127ø25'E at 460 m altitude.
HATAKEYAMA
ET AL.:
AIR POLLUTANTS
1320 JST hadpassed throughthe Seoul,Korea,metropolitan
OVER SEAS AROUND
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The Yellow Sea (October 7-8, 1991). Sincewe made only level flightsat about3000 m duringthe roundtrip to Seoul,no drasticchangesin the mixing ratiosof ozoneand of anthropogenic pollutants. During the flight on October6, the NOx* and ozone NOx* were observed.The averagemixing ratiosof ozone mixing ratiosstayedrelativelyconstantat high altitude and NOx* were 51.0 ppb and 0.48 ppb, respectively,for (Figure3), andNOx* beinghigherthanthat recordedonthe October7 at an averagealtitudeof 3140 m, and 45.2 ppb earlier half of the previousday. The same air mass as and 0.46 ppb, respectively,for October8 at an average sampledduring the latter part of the October 5 flight altitudeof 2830 m. However,it is clearfrom Figures4 and apparently prevailedoverthe EastChinaSea,and gavethe 5 thatthemixingratioof ozoneaboveChejuIsland(between highNOx* mixingratio. NO wasbelowthe detection limit. 1200 and 1230 JST on October 7 and between 1530 and However,the profilesof ozone,NOx*, andrelativehumidity 1600 JST on October8) was relativelyhigh. It was also between 1300 and 1330 JST showed clear structure. A high as expectedabovethe SeoulMetropolitanarea (after strong negative correlationbetween ozone and relative 1500 JST on October7) andnearNagasaki(after 1645 JST humidity(see Figure 9a) as well as a positivecorrelation on October8). The back trajectoryanalysisshowsthat the between NOx* andrelativehumidity(Figure9b) werenoted. air masshad left northwestEurasia4 daysearlierandpassed Thesecorrelations indicatethat downwardtransportof upper throughBaikal as well as Manchuriaand the Yellow Sea. atmospheric air and upwardtransportof boundarylayer air Thusthe air masson eitherdayhadbasicallythe samenature, took placesporadicallyin thisarea. beingunaffectedby localpollutionexceptfor the abovethree On both days the mixing ratios of ozone at the lower areas. The Sea of Japan (October 10-11, 1991). A typhoon altitude(-460 m) were higher(average50.6 and 56.9 ppb on October5 and October6, respectively)than those at wasmovingnearthe southcoastof Japanon October10 and higheraltitude(-3000 m) (average28.9 ppb and 42.2 ppb 11. Thereforethe wind blew mainly from the northor the in the observation areaoverthe Seaof Japan,and onOctober5 andOctober6, respectively) exceptfor thosein northeast theverylow levelsof NOx* observed. the air massbefore1230 JST on October5, whichoriginated thismayhavecaused from the upper layer. This differs from the normal On October10 the mixingratio of NOx* was quitelow at distributionof lower troposphericozone in the areas 3000 m (average0.17 and 0.14 ppb) as well as at 460 m unaffected by anthropogenicpollution [ChaOqeldand (average0.10 ppb). Kondo et al. [1987] reportedthat the Harrison, 1977; Logan et al., 1981], and also differsfrom mixingratioof NOy between the latitudes of 30 and35øN that in the areasaffectedby anthropogenic pollutionbut with aroundJapanis fairly constant at about0.20 ppb. TheNOx* low photochemical activity[Gregoryet al., 1984]. In both mixing ratios we measured at 3000 m altitude were cases,ozone mixing ratio is normally higher at higher consistent with Kondo et al.'s results when we take into the difference between ourNOx* andtheirNOy. altitude. However,if we take into accountthe presence of a account was different stationaryfront in thisarea,we canspeculate that an air mass Although the season.'ofthe measurements in the lowerlayerwhichcontained muchozoneand NOx (October versus January-February),the pattern of back pushedup anotherair masswhichcontainedlessozone. The trajectorieswas similar. Both the trajectoriesstarted in latterair masswas suggested by backtrajectoryanalyses to northeast Asia and traveled over the Sea of Japan. have been continentaloutflow originatingin the southern Apparently,the similarity of the origin of the air masses partof Chinaandtravelingoverthe EastChinaSeafor more broughtaboutthe agreementof the mixingratiosof nitrogen oxides. than 1 day. The back trajectoryindicates(Figure 10) that the air sampledat 1226 JST (altitudeof 3000 m) hadstartedaround Baikal 4 daysearlier,passedoverlessindustrialized partsof 60 2 (a) the Asiancontinentandstayed2 daysoverthe Seaof Japan. The air sampledat 1351 JST (altitude of 460 m) stayed abovethe Sea of Japanfor morethan 3 days(Figure 11). 1.5 40 Thustheresultsof thebacktrajectorycalculations agreevery well with the observations.The backtrajectorycalculations • 30 alsoexplaintheverylow levelof NOx* observed at 460 m. The relative humidity of the air at 3000 m (Figure 6; 20 1130-1300 JST and 1430-1500 JST) was quite low (less than 5%). The mixing ratios of ozoneduringthesetwo 10 m"0•••,•32 R2= periodswere relativelyhigh; average58.1 and 57.2 ppb, 0 m • 0.5 respectively.Thus the air massmust have descended from 20 30 40 50 the upper layer. In contrast, after 1500 JST the mixing ratio RH/% of ozonesuddenlydroppedand that of NOx* rose. The at thistime. Clearly,the air Figure 9. Correlationof (a) ozone and (b) NOx* with relativehumidityalsoincreased relativehumidityfor the air sampledbetween1300 and 1330 massafter 1500 JST is differentfrom that sampledearlier. JST on October 6. The result of the back trajectory calculationsfor these area. This could be the cause of the observed elevated levels
(b) Q.., ., "___ .,.,•I•W'_•
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60 ................ f.......................... i............ õ0................... i....... 4O
40
3O
30
2O
20
1O0
110
120
130
140
150
1O0
110
120
130
140
150
Figure 10. Backtrajectoryof the air masssampledat 1226
Figure 11. Backtrajectoryof the air masssampledat 1351
JST on October 10 at 35 ø20'N, 131 ø7'E at 3000 m altitude.
JST on October10 at 36 ø562q, 133 o57'E at 460 m altitude.
sampleswas consistent with thisexplanation.This air parcel passedby the island of Honshu, and thus it probably containedlocalpollutionfrom Japan. On October11 the air massat higheraltitude(-3000 m) could be divided into four parts on the basis of relative humidit),(Figure7). Namely,the air masses(1) from 1130 to 1200 JST, (2) from 1200 to 1230 JST, (3) from 1300 to 1400 JST, and(4) from 1400 to 1430 JST. The relativehumidityin air mass1 wasas highas 60%. The averageozonemixingratioin thisair masswas51.7 ppb.
background ozone mixing ratios within theboundary layerof thisarea[Akimotoet al., 1995]. Characteristics
of the Air
Masses
and the Relation-
ship between NOx* and Ozone Mixing ratios. On the basisof the NOx*, ozone,temperature, and humiditydata, theNOx* observed duringthiscampaign canbe dividedinto threecategories, independent of areaand dateas indicatedin Table 2 and summarized in Table 3. Backtrajectories for thesethreecategories suggest distinctair masshistories.The air masseslisted passedover Baikal , Mongolia, and/or
NOx* was high (average0.66 ppb). The back trajectory Manchuria from northwest Eurasia, and thus had the showsthat this air parcelpassednear the islandof Honshu andit musthavebeenaffectedby localpollution(Figure12). 60 -:...............f...............:...............:...............!............... Air mass4 had quitelow humidity(lessthan 5ø/3)andvery highmixingratiosof ozone(average66.8 ppb). Thereforeit is plausible to assumethat the impact of the upper atmosphere on this air masswas large. Air masses2 and 3 õ0 ..................................... seemto be similarair mass. The relativehumidity(-10%) wasslightlyhigherthanthat of air mass4. The mixingratio of ozonewas lowerthanthat of air mass4 but higherthan that of air mass1 (average57.4 and 56.7 ppbfor air masses 2 and3, respectively), andtheNOx* mixingratiowaslower than that of air mass1 (average0.27 and 0.44 ppbfor air masses2 and 3, respectively).Thesedata indicatethat the air of the boundary layer was convectedto the free troposphere in thisarea. 30 .................................... On this day the air mass of the lower atmosphere contained highmixingratiosof NOx* (average1.78 ppb),in clear contrastwith the very low mixingratio (0.10 ppb) of
:'"'
'
./::
NOx* observedat 460 m on October10. Back trajectory 20 : ' analysisindicates thatthisair masswastransported overthe 1O0 110 120 130 140 150 islandof Honshu2 daysearlier,whichcouldbe the reason for the highNOx* observations. Ozoneat 460 m was41.0 Figure 12. Backtrajectoryof the air masssampledat ] 142 ppb on average, which is a value representativeof JST on October11 at 38 øO•T, 136ø48'E at 3000 m altitude.
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Table 2. AverageValuesofNOx*, 0 3, Temperature, andRelativeHumidityObserved at -3,000 m AltitudeOverhe OceanAroundJapan(1991 PEACAMPOT,October5-11). Area
Date
Data
[NOx*]
[O3]
ppb Nagasaki to Yoron andback
Relative
'C
humidity, %
Oct.6, 1991
[05-1] [05-2] [05-3] [06-3]
Oct.7, 1991 Oct.8, 1991
[07] [08]
0.51+0.15 0.47+0.14
51+6 45+4
8.0+1.4 10.6+2.7
6+5 7+9
Nagasaki Oct.10, 1991 to Niigata and back Oct.11, 1991
[10-1]
0.17+0.03
57+4
10.4+0.6
Vcry low
[10-2] [11-1]
0.69+0.075 42+25 0.79+0.065 52+51'
[11-2] [11-3]
0.41+0.10 56+2 10.8+0.7 0.40_--+-0.06 67_--+-2 12.7_--+-0.9
Nagasaki to Seoul
Oct.5, 1991
Temperature,
ppb
0.56+0.04 0.50+0.02 1.96-t-0.15' 1.25_--+-0.23'
52+1 64 +3 29-t-3' 43_--+-3*
9.6+0.1 10.9+0.6 12.7-t-0.5' 12.6_--+-1.2'
Very low Very low 72-t-5' 49_--+-11'
and back
9.3+_0.25 9.2+0.75
69+__45 58+65 8+5 Vcry low
Air masses thatpassed overBaikal,Mongolia,and/orManchuriafromnorthwest Eurasia.
*)Airmasses thatpassed overindustrial areaalongtheYangtze River. '•)Airmasses thatstayed abovetheSeaof Japan forabout3 days.
characteristics of thebackground air massin thisregion. On theotherhand,thetrajectory fortheair masswithhighNOx* mixingratios(indicatedwith an asterisk)showedthat it passedoverindustrialareaalongthe YangtzeRiver. This resultsupports the notionthat anthropogenic emissions in
2. The sizeof the ellipsoidrepresents onestandarddeviation of the averagemixingratiosof NOx* andozone(the center of the ellipsoidsshowsthe averagevalues). Error bars represent the minimumandthe maximumfor eachvalue. In mostcasesin the background troposphere, NOx (= NO +
this area have affected the chemical characteristics of the
NO2) is the limiting factor for photochemicalozone formationandthusa positivecorrelationis expectedbetween ozoneandNOx* mixingratios[Fishmanet al., 1979;Liu et
oceanicair in thisregionof thePacificrim. Thethird group (indicatedwith a dagger)contains NOx* and ozonemixing ratiosbetweenthoseof two previousgroups.Thetrajectories of theseair masseswere very short,that is, the velocities were very slow. The air massesof this groupremained abovethe Seaof Japanfor about3 days. Duringthisperiod the sunshine wasweak andphotochemically producedozone did not accumulate.Theseair masseshad passedover the Note Peninsulaof Honshuon the previousday. Thus althoughoriginallytheyshouldhavebeenclean,somelocal pollutionwasaddednearHonshu. In Figure13 the ozonemixingratiois plottedagainstthe NOx* mixing ratio at 3000 m for each air mass. The numbersin bracketscorrespond to the datanumbersin Table
al., 1987; Trainer et al., 1993]. Our results,in contrast, showa negativecorrelation.Apparently, the ozoneobserved at 3000 m duringthis experimentwas mainly transported
fromthe upperatmosphere andphotochemical formationdid notplay a majorrole. Photochemical ozoneformationin the boundarylayerwasobserved onlyovertheEastChinaSea. S02
Of the 48 samplescollectedduring the six flights, 23
samples showedSO2 mixingratiosabovethedetection limit of the analyticaltechniqueemployedin thisexperiment (0.03 ppbvat 600 L of sampleair volume). The mixingratiosof
Table 3. Representative NOx* andOzoneMixingRatiosof Air Masses in theFree Troposphere AroundJapanandTheirBackTrajectories [NOx*] ppb
[03] ppb
1.2'
>50
