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JournalofEnvironmentalProtection,2011,2,162-167doi:10.
4236/jep.
2011.
22018PublishedOnlineApril2011(http://www.
SciRP.
org/journal/jep)Copyright2011SciRes.
JEPChangesinTemperaturesinOkayamaAreaComparedwithDifferentUrbanizationAreas,JapanNorikoSakano1*,NobuyukiMiyatake1,ShokoMurakami1,TakeshiSuzue2,TomohiroHirao2,KeikiOgino31DepartmentofHygiene,FacultyofMedicine,KagawaUniversity,Kagawa,Japan;2DepartmentofPublicHealth,FacultyofMedicine,KagawaUniversity,Kagawa,Japan;3DepartmentofPublicHealth,OkayamaUniversityGraduateSchoolofMedicine,DentistryandPharmaceuticalSciences,Okayama,Japan.
Email:snoriko@med.
kagawa-u.
ac.
jpReceivedNovember11th,2010;revisedJanuary10th,2011;acceptedMarch1st,2011.
ABSTRACTToinvestigatethechangesintemperaturesinOkayamaareacomparedwithdifferentlevelsofthreeurbanizationareassuchasTsuyama,TokyoareasandHachijoislandinJapan.
DataoftemperaturesinOkayama(1891-2009),Tsuyama(1943-2009),Tokyoareas(1876-2009)andHachijoIsland(1907-2009)inJapanwasobtainedfromJapanMeteorologicalAgency.
Changesintemperaturesin4areasinJapanwereanalyzedandcompared.
Byusingdatafrom1943to2009,someparametersoftemperaturesweresignificantlycorrelatedwithyears.
ThechangeinparametersoftemperaturesinHachijoIslandwascalmestamong4areas.
ThechangesinmeantemperatureinAugustandinayearinOkayamaareafor50yearswerethehighest(August:1.
55C,Year:2.
05C)among4areas.
Inaddition,correlationcoefficientratebetweenyearsandthenumberofdaysover35CinAugustinOkayamaareawashighest(r=0.
407,p=0.
0037).
ParametersoftemperaturesweregraduallyincreasedwithyearsinOkayamaarea,especiallyinrecentyears.
However,thoseassociationswerenotclearlynotedinHachijoIsland.
Inconclusion,globalwarminginOkayamamightbeacceleratedmorerapidlythanthatinTokyoareainrecent50years.
Keywords:Temperature,GlobalWarming,Urbanization,OkayamaArea1.
IntroductionGlobalwarminghasbecomeaseriousissueforhumanbeings.
TheFourthreportoftheIntergovernmentalPanelonClimateChange(IPCC)at2007onclimatechangehasforecastthatglobalwarmingwillhaveamajorimpactonhealthconditions[1].
Globalaveragetemperaturesareprojectedtoincreasebetween1.
8and4.
0°Cbytheendof21stcentury[1].
HeatwavessuchasShanghaiin1998andParisin2003mayberepresentativeoftheincreasesinshort-termclimatechangeevents[2-5].
IthasalsoreportedthatthelevelsofatmosphericCO2concentrationsareincreasingsincethelastcentury[6,7].
Inaddition,globalwarminghasaccelerated,andchangesintemperatureswereremarkablynotedsincethe1980s,resultinginincreasednumbersofheatrelateddisorderinsummer[8,9].
Mostcitiesshowalargeheatislandphenomenon,registering5-11Cwarmerthansurroundingruralareas[10].
Onlocalandregionalscales,changesinlandcovercansometimesexacerbatetheeffectofgreenhouse-gas-inducedwarming,orevenexertthelargestimpactonclimaticconditions.
WehavealsopreviouslyreportedthathighertemperatureswerecloselylinkedtohigherambulancetransportsinOkayamaarea,Japan[11].
However,accurateanalysisofwarming,whethertemperatureisactuallyincreasinginOkayamaareaandwhataffectsthiswillhave,remaintobeinvestigated.
TheaimofthisstudywastoinvestigatethecurrentstatusofglobalwarminginOkayama.
Inaddition,wecomparedvariousparametersoftemperaturesbetweenvariousareasfromtheviewpointoftheheatislandeffects.
2.
Methods2.
1.
StudyAreaOkayamaareainOkayamaPrefectureisonthesouthernChangesinTemperaturesinOkayamaAreaComparedwithDifferentUrbanizationAreas,Japan163shoreofHonshuIsland.
Thepopulationof700000peopleissituatedonOkayamaarea.
CurrentlyseveralpublicofficesofChugokudistrictarelocatedinOkayamaarea.
AlthoughthesurroundsofOkayamaareahadbeenusedprimarilyaspaddyfieldsforagriculture,recentlytheyhaveundergonerapidchanges,developingintoresidentialand/orcommercialareas(Figure1).
Weselectedthreeareas,Tokyoasthecitypartarea,andTsuyamaorHachijoIslandastheprovinces,fortheanalysisincomparisonwithOkayamacity,Japan.
TsuyamaareainOkayamaprefectureisonthecentralofChugokuarea,Japan.
Thepopulationof110000peopleissituatedontheTsuyamaarea.
TsuyamaareahadbeenusedprimarilyaspaddyfieldsforagriculturecomparedtoOkayamaarea(Figure1).
TokyoareaisthelargestmetropolitanareainJapananditspopulationisabout13.
0million.
Tokyocentral(8.
8millionpopulation,621km2)islocatedinthecenterofthemetropolitanarea,andismostlyurbanizedinJapan(Figure1).
HachijoIsland(65.
52km2)islocatedatthesouthfromTokyoarea(287km)andthepopulationof9000peopleissituatedontheHachijoIsland.
IslandisaffectedbytheKuroshioCurrent(inanoceanicclimatezone)(Figure1).
2.
2.
TemperaturesDaily,monthlyandannualtemperaturesinOkayama,Tsuyama,TokyoareaandHachijoIslandinJapanfortherequiredperiodswereobtainedfromJapanMeteorologicalAgency(http://www.
data.
jma.
go.
jp/obd/stats/etrn/index.
php,accessed27Jan,2010).
MeantemperatureinAu-TsuyamaAreaTokyoAreaOkayamaAreaHachijoIslandFigure1.
FourstudyareasinJapan.
(CraftMap:http://www.
craftmap.
box-i.
net/map.
php,accessed6Aug,2010).
gust,meantemperatureinayear,meanofthehighesttemperaturesinAugust,meanofthehighesttemperaturesinayear,meanofthelowesttemperaturesinAugustandmeanofthelowesttemperaturesinayear(Okayamaarea:1891~2009,Tsuyamaarea:1943~2009,Tokyoarea:1876~2009,HachijoIsland:1907~2009).
ThenumberofdaysoverthelevelofvarioustemperaturesinAugustwasalsousedforanalysis(1961~2009).
2.
3.
StatisticalAnalysisPearson'scorrelationanalysisbyusingStatisticalPackageofSPSS12.
0JforWindowswasperformedtoexaminethesignificanceofthelinearrelationshipamongcontinuousvariables:pInaddition,joinpointregressionprogram(NationalCancerInstituteJoinpointregressionprogram,version3.
4.
3,http://srab.
cancer.
gov/joinpoint/,accessed18August,2010)wasalsousedtoinvestigatedthewherethedifferentlinesoftemperaturesareconnectedtogether.
3.
ResultsSimplecorrelationanalysisbyPearson'scorrelationbetweenyearsandparametersoftemperaturesin4areasissummarizedinTable1.
AllparametersoftemperaturesinOkayamaarea(1891~2009)weresignificantlycorrelatedwithyears.
Tokyoarea(1876~2009)alsoshowedsignificantrelationshipbetweenvariousparametersoftemperaturesandyears(Table1).
InTsuyamaarea,someparametersoftemperaturesi.
e.
meantemperatureinayear,meanofthehighesttemperaturesinayearandmeanofthelowesttemperaturesinayearwassignificantlycorrelatedwithyears.
Toadjusttheobservationperiod,byusingdatafrom1943to2009,wealsoanalyzedtherelationshipbetweenvariousparametersoftemperaturesandyearsin4areas(Table2).
InOkayamaarea,allparametersexceptmeanofthehighesttemperaturesinAugust,werealsocorrelatedwithyears.
Meantemperatureinayear,meanofthehighesttemperaturesinayearandmeanofthelowesttemperaturesinayearweresignificantlycorrelatedwithyearsinTsuyamaandTokyoareas.
MeanofthelowesttemperaturesinAugustinTokyoareaswasalsocorrelatedwithyears.
However,noparameterswerecorrelatedwithyearsinHachijoIsland.
CorrelationcoefficientsbetweenvariousparametersoftemperaturesandyearsinOkayamaareawerethehighestamong4areas.
Fromsingleregressionline,positivechangeinmeantemperaturefor50yearswascorrespondedto2.
05CinOkayamaarea,Japan(Table2).
However,thechangeintemperatureswasthelowestinHachijoIslandamong4areas.
Inaddition,usingsingleregressionlineinTables1and2,positivechangesintemperaturesCopyright2011SciRes.
JEPChangesinTemperaturesinOkayamaAreaComparedwithDifferentUrbanizationAreas,JapanCopyright2011SciRes.
JEP164for50yearsinTable2werehigherthanthoseinTable1inOkayamaarea.
Therefore,positivechangesintemperaturesfor50yearswereacceleratedinOkayamaarea.
InTokyoareas,positivechangesinmeantemperatureinayearandmeanofthelowesttemperaturesinayearwerealsoaccelerated.
However,otherparametersinTokyoareasandHachijoIslandwerenotaccelerated.
Inaddition,usingjoinpointregressionprogram,weanalyzedthepointofchangeinmeantemperaturein4differentareas.
ThepointofchangeinmeantemperaturesinTokyowas1921,thatinOkayamawas1973(Figure2)andthatinTsuyamawas1984.
However,thepointofchangeinmeantemperatureinHachijoIslandwasnotnoted.
Finally,therelationshipbetweenthenumberofdaysofovervarioustemperatureswhichseemtoberelatedtoheatdisorderispointedoutandyearswasalsoevaluated(Table3).
Thenumberofdaysofover33Cand35CinOkayamaareawassignificantlycorrelatedwithyears.
Especiallycorrelationcoefficientbetweenthenumberofdaysofover35CandyearsinOkayamaareawasthehighest(r=0.
407,p=0.
0037)(Figure3).
Table1.
Simplecorrelationanalysisbetweenyearsandparametersoftemperatureinfourareas.
rpSingleregressionlineChangesintemperatures(C)for50yearsOkayamaprefectureOkayamaarea(from1891to2009)MeantemperatureinAugust0.
416inayear0.
648inAugust0.
3280.
0003y=0.
012x+8.
9650.
60Meanofthehighesttemperaturesinayear0.
668inAugust0.
518inayear0.
580inAugust0.
1300.
2939y=0.
006x+14.
8140.
30Meantemperatureinayear0.
458inAugust0.
0430.
7299y=0.
003x+25.
8900.
15Meanofthehighesttemperaturesinayear0.
4470.
0001y=0.
014x–8.
1070.
70MeanofthelowesttemperaturesinAugust0.
1320.
2866y=0.
005x+11.
6710.
25Meanofthelowesttemperaturesinayear0.
4430.
0002y=0.
014x–18.
9680.
70TokyoprefectureTokyoarea(from1876to2009)MeantemperatureinAugust0.
556inayear0.
887inAugust0.
353inayear0.
728inAugust0.
714inayear0.
917inAugust0.
2850.
0036y=0.
006x+15.
1360.
30Meantemperatureinayear0.
3500.
0003y=0.
005x+7.
6240.
25MeanofthehighesttemperatureinAugust0.
2490.
1111y=0.
007x+15.
8190.
35Meanofthehighesttemperatureinayear0.
2900.
0029y=0.
004x+12.
4820.
20MeanofthelowesttemperatureinAugust0.
3640.
0002y=0.
008x+8.
1780.
40Meanofthelowesttemperatureinayear0.
416inTemperaturesinOkayamaAreaComparedwithDifferentUrbanizationAreas,Japan165Table2.
Simplecorrelationanalysisbetweenyearsandparametersoftemperaturesinfourareasfrom1943to2009.
rpSingleregressionlineChangesintemperatures(C)for50yearsOkayamaprefectureOkayamaareaMeantemperatureinAugust0.
554inayear0.
833inAugust0.
2230.
0701y=0.
014x+4.
9960.
70Meanofthehighesttemperaturesinayear0.
558inAugust0.
619inayear0.
811inAugust0.
1300.
2939y=0.
006x+14.
8140.
30Meantemperatureinayear0.
458inAugust0.
0430.
7299y=0.
003x+25.
8900.
15Meanofthehighesttemperaturesinayear0.
4470.
0001y=0.
014x–8.
1070.
70MeanofthelowesttemperaturesinAugust0.
1320.
2866y=0.
005x+11.
6710.
25Meanofthelowesttemperaturesinayear0.
4430.
0002y=0.
014x–18.
9680.
70TokyoprefectureTokyoareaMeantemperatureinAugust0.
2330.
0581y=0.
013x+0.
8410.
65Meantemperatureinayear0.
825inAugust0.
0160.
8956y=0.
001x+33.
094–0.
05Meanofthehighesttemperaturesinayear0.
4260.
0003y=0.
013x–5.
9600.
65MeanofthelowesttemperaturesinAugust0.
3960.
0009y=0.
022x–18.
9661.
10Meanofthelowesttemperaturesinayear0.
889inAugust0.
0080.
9505y=0.
002x+26.
1210.
01Meantemperatureinayear0.
1940.
1152y=0.
005x+9.
0670.
25MeanofthehighesttemperatureinAugust–0.
1300.
2938y=0.
004x+38.
272–0.
20Meanofthehighesttemperatureinayear0.
0730.
5565y=0.
002x+17.
7220.
10MeanofthelowesttemperatureinAugust0.
1130.
3625y=0.
004x+17.
1880.
20Meanofthelowesttemperatureinayear0.
1530.
2175y=0.
004x+7.
5930.
20Figure2.
ChangepointofannualmeantemperaturesinOkayama,Japan(1891~2009).
Copyright2011SciRes.
JEPChangesinTemperaturesinOkayamaAreaComparedwithDifferentUrbanizationAreas,JapanCopyright2011SciRes.
JEP166Table3.
SimplecorrelationanalysisbetweenyearsandnumberofdaysovervarioustemperaturesinAugustfrom1961to2009.
OkayamaareaTsuyamaareaTokyoareaHachijoislandrprprprpNumberofdaysover30C0.
0710.
63010.
0530.
71690.
0160.
91130.
1180.
4213Numberofdaysover31C0.
0730.
61840.
0040.
97990.
0740.
61270.
1070.
4628Numberofdaysover32C0.
1730.
23460.
0860.
55520.
0230.
87310.
0850.
5637Numberofdaysover33C0.
3430.
01590.
0690.
63840.
0770.
59680.
0580.
6905Numberofdaysover34C0.
2660.
06430.
1010.
49170.
1300.
3748Numberofdaysover35C0.
4070.
00370.
0000.
99780.
1250.
39294.
DiscussionWefirstlyinvestigatedthechangesinparametersoftemperaturesamong4differenturbanizationareassuchasOkayama,Tsuyama,TokyoareasandHachijoIsland,Japan.
ParametersoftemperaturesweregraduallyincreasedwithyearsinOkayamaarea,especiallyinrecentyears.
Inaddition,thechangepointof1973inmeantemperaturemaybereflectedthatheatislandeffectinOkayamaareawasremarkablyaccelerated.
AccordingtotheresearchofOsakainJapan,themeanwarmingrateinOsakasurfaceairtemperatureisabout2.
0Covertheperiodfrom1883to2006,atleasthalfofwhichcanbeattributedtotheurbanheatislandeffects[12].
However,thissurfaceairtemperaturewarmingwasnotasstrongasthegroundwarmingrecordedinthesubsurfacetemperatureprofiles.
Therefore,theanthropo-genicthermalimpactsonthesubsurfacecanbemorepersistentandprofoundthantheimpactsontheatmosphere.
Figure3.
Simplecorrelationanalysisbetweenthenumberofdaysover35CandyearsinOkayamaarea,Japan(1961~2009).
Insomepreviousreports,therelationbetweenhightemperaturesandheatstrokeinJapan[16-18].
Nakaietal.
investigatedheat-relateddeathsinJapanfrom1968through1994andheat-relateddeathsweremostpronetooccurondayswithapeakdailytemperatureabove38C[16].
Inaddition,theyreportedthatincidenceofheat-relateddeathsshowedandexponentialdependenceonthenumberofhotdays[16].
Piveretal.
reportedthatheatstrokewasassociatedwithprolongedexposurestohigherairtemperaturesthatusuallyoccurinthesummermonthsofJulyandAugustin1980-1995inTokyo.
ResidentsinTokyowerealsooftenexposedsimultaneouslytohighconcentrationsofairpollutants[17].
Quietal.
reportedthatanunusualhotspellin1999wasfollowedbyahighmortalityrateinHokkaido,Japan[18].
WehavealsopreviouslyshowedthathighertemperatureswerecloselylinkedtoambulancetransportsinOkayamaarea,Japan[11].
Taniguchietal.
reportedthatsubsurfaceenvironmentalindicatorswereevaluatedfromthreepointsofviewi.
e.
humanactivities,climatechange,andcharacterofurbanizationandsocialpolicies.
Heatislandeffectduetourbanizationcreatessubsurfacethermalcontaminationinmanycities[13].
AveragesubsurfacetemperatureprofilesinfourAsiancities(Tokyo,Osaka,SeoulandBangkok)werecomparedandanalyzedtoevaluatetheeffectsofsurfacewarming[14].
ThemagnitudeofsurfacewarmingisevaluatedtobethelargestinTokyo(2.
8C),followedbySeoul,OsakaandBangkok.
Andthisobservationshowedmeandepthofdeviationfromtheregionalgeothermalgradientineachurbanareamaybeausefulindicatorofthehistoryofurbanization.
Thecombinationoftheheatislandeffectduetourbanizationandglobalwarmingonsubsurfacetemperaturesalsorelatestoglobalgroundwaterqualityissues.
Thisrelationshipholdsbecauseincreasedsubsurfacetemper-aturesalterthegroundwatersystemchemicallyandmicrobiologically[15].
Inthisstudy,wecomparedpointsofchangeinmeantemperatureamong4areas,andwefoundthatpointofChangesinTemperaturesinOkayamaAreaComparedwithDifferentUrbanizationAreas,Japan167changeinmeantemperatureinTokyowas1921,thatinOkayamawas1973andthatinTsuyamawasin1984.
Therefore,itseemsreasonabletosuggestthatsimplydealingwithheatislandeffectinOkayamaareai.
e.
innovationofthethermalenergymetabolismincitiesandindividualcopingwithhightemperaturesisurgentlyrequiredinOkayamaaswellasTokyoarea,Japan.
Inaddition,thepointofchangeinmeantemperaturemaybegoodparameterofurbanizationinJapan.
Potentiallimitationstillremainsinthisstudy.
Thechangesinparametersoftemperatures,whichwerenotedin4areas,maynotapplyforallareasinJapan.
Therefore,wecouldnotaccuratelyevaluatethechangesintemperaturesinJapan.
FurtherstudiesarerequiredtoprovethechangesintemperaturesandheatislandeffectinJapan.
Inconclusion,themeantemperatureinOkayamaareaisrisingintentionallyhigherthanthatinTokyoarea,especiallyinrecentyears.
Thenumberofdaysofover33Cand35CinonlyOkayamaareawassignificantlycorrelatedwithyears.
5.
AcknowledgementsWegratefullythanktoMrs.
MichiyoMitaniforassistanceofdatapreparation.
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JEP