is it related to global warming? - apec typhoon chang - 21... · is it related to global warming?...
TRANSCRIPT
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RecordBreakingIncreaseinTaiwanTyphoonRainfallintheRecentDecade:
IsitRelatedtoGlobalWarming?
C.P.Chang1,2,Y.T.Yang1, H.C.Kuo1,C.H.Sui1,YH.Lei3,XH.Lin4,andFM.Ren5
1DepartmentofAtmosphericSciences,NationalTaiwanUniversity2DepartmentofMeteorology,NavalPostgraduateSchool3 InstituteofRemoteSensingApplications,ChineseAcademyofSciences4 FujianMeteorologicalBureau,ChinaMeteorologicalAdministration5 NationalClimateCenter,ChinaMeteorologicalAdministration
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Rank Year Typhoon NameTotal
(h)Rainfall(mm)
1 2009 Morakot 45 89962 2001 Nari 75 81083 2008 Sinlaku 48 81054 2005 Haitang 32 55895 1996 Herb 16 48366 1989 Sarah 38 46557 1960 Shirley 24 46378 2007 Krosa 23 39369 2004 Mindulle 41 3856
10 2008 Jangmi 25 380011 2008 Kalmaegi 23 376312 2005 Talim 17 3526
Table1:Thetwelve typhoonsin19602011withtotalrainfalloverTaiwan exceeding3500mm duringthethreephases.Theeightsince2004arehighlighted.
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Introduction
GlobalWarming Increasingvaporcapacityincreasingrainintensityandextremerainfall.
ClimatemodelssimulatedincreasingtrendofextremerainfallsimulatedoverNHlandarea;observedoverEurope&N.America,butunclearoverAsianmonsoonregion.
VerylargeincreasingtrendofextremerainfallreportedinTaiwansince1998,attributiontoglobalwarmingisthesubjectofongoingdebate(increasingvaporandpositivefeedback?)
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S-K Min et al. Nature 470, 378-381 (2011) doi:10.1038/nature09763
Geographical distribution of trends of extreme precipitation indices (PI) during 195199.
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RainfallinEastAsiaSummerMonsoon
ExtremerainfallcontributedbybothmonsoonandTropicalCyclones(TCs)
TCsinfluencedbytropicalwesternNorthPacificconditions(upstreamofEastAsianlandmass)
Extremerainfallinfluencedbyexternalfactorsnotpartoflocalthermodynamicconditions
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Typhoonrainfalllineartrends
Intensity AmountFrequency
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PercentageofTCrainfallinTotalRainfall
PercentageofTCrainfallinExtremeRainfall(90th Percentile)
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NEC
YV
SC
HN
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Taiwan90th percentile
Total19.5%
Monsoon10.9%
Overestimate~79%
Total46.2%
Monsoon12.2%
Overestimate
(byamount)
(byevents)
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SomostofChinaSummerMonsoonAreathetrendofextremerainfallwasunderestimated,becauseoflessTCrainfall.IfTCinfluenceisremoved,extremerainfalltrendwillbemoreclear.
Taiwanisanexception. WhatcauseTaiwanstyphoonextremerainfallincrease?
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2006Kalmaegi 925 hPa
2009Morakot 925 hPa
Pengchiayu
Keelung
I-Lan
Hualian
Chengkung
Taitung
LanyuTawu
Hengchun
Penghu
Tainan
Kaohsiung
Hsinchu
Taichung
Jiyehtan
AlishanYushan
Tamshi
Taipei
Anbu Zhuzihu
119E 120E 121E 122E 123E21N
22N
23N
24N
25N
26N
N
( )b
119E 120E 121E 122E 123E21N
22N
23N
24N
25N
26N
C
( )c ( )d
119E 120E 121E 122E 123E21N
22N
23N
24N
25N
26N
S
2003Morakot 925 hPa
C
N
S
( )e( )a
0 1000 2000 3000(m)
19602011:21hourlystations,84landfallingtyphoons
MaximumTerrainInteraction
MinimumTerrainInteraction
MaximumSWmonsoonInteraction
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13
PreLandfall
OverLand
EXit
TyphoonTrackPhases
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PReLandfall
2008
2004
2009
20052007
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OverLand
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EXit
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PhaseTrack Type
PR OL EX
N 1960 2132 1458C 1305 1558 1467S 1033 812 572
Table2:The12hourrainfallintensity(mm)forthethreetracktypesduringthethreephases.
1.Terraineffectdominates2.Afterexit,SWmonsooninteractionimportant
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Frequency 19602003 20042011N 21(44.6%) 5(31.3%)C 15(31.9%) 8(50.0%)S 11(23.4%) 3(18.8%)
Duration(hour) 19602003 20042011N 15.9 24.0C 23.9 23.3S 21.7 20.0
Table3:Theabsoluteandrelative(%)frequencyanddurationoftheN,C,andStyphoonsbeforeandafter2004.
(Chu,P.S.etal.,2012, GRL: SlowingtrendofNCEP/NCARandERA40steeringflowsfrom1959 2009.)
1/3
+1/2
+2/3
Totalfrequency+Nduration+
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Composite Rainfall
(Hsu,Kuo andFovell 2013,JAS)
Nduration+
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Figure 6. a) Time series of rainfall intensity from 1960 to 2011 for the pre-landing (PR, blue), overland (OL, black) and exit (EX, red) phases for weak and medium intensity (Category 1-3) typhoons. Grey vertical columns indicate years with no typhoons of the three leading track types. The table inside the panel lists the averaged yearly rainfall intensities of the three phases during the first half (1960-1985, left column) and second half (1986-2011, right column) of the 52 year period. The two sub-periods are indicated by double end arrows above the panel. b) Same as a) except strong types (Category 4-5) are included. The rainfall intensity of each strong typhoon is indicated by the respective colored dots.
Fig6a112.5 110.1 2.1%128.7 129.0 0.2%78.2 92.9 18.8%
Fig.6b112.2 112.1 0.1%128.8 130.4 1.2%75.9 92.0 21.2%
60 64 68 72 76 80 84 88 92 96 00 04 08 12
Year
0
50
100
150
200
250
300
rain
inte
nsit
ym
mh
r(
/)
112.2
128.8
75.9
112.1
130.4
92.0
( )b
60 64 68 72 76 80 84 88 92 96 00 04 08 12
Year
0
50
100
150
200
250
300
rain
inte
nsit
ym
mh
r(
/)
112.5
128.7
78.2
110.1
129.0
92.9
( )a
DecadalRainfallIntensityChanges?
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HugeincreaseofTCrainsignifiesglobalwarming/climatechangeeffects?
PrelandfallandOverland,theincreaseisduetolongerdurationandslightchangeoftracks.
Resultofstrongcontrolbyterraineffect(trackchangeismesoscale)
AftercenterexitsTaiwan,increaseduetostrongermonsoonTCinteraction.
Linktoglobalclimatechangepossible:(butnotTCintensity)
GlobalWarming?orNaturalVariability?
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GlobalWarmingorNaturalVariability?
Strengthening ofNHsummermonsoonandtropicalcirculationsconsistentwithslowersteeringflowofTaiwanTCsandenhancedmonsooninteractionafterTCleavesTaiwan.
GWpredictsweakening oftropicalcirculations.
(Wang,B.etal.2013,PNAS)
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Conclusions IncreasingextremerainfalltrendinAsianmonsoonlandarea
maskedbydecreasingTCrainfallactivity.Taiwanisanexception. PrelandfallandOverland,TCrainfallincreaseisduetolonger
durationandslight(mesoscale)changeoftracks. Localterraineffectcontributestoanimpressionofclimatechange,
yetitstronglyconstraintstherainintensityandmasksbroadscaleclimatechange.
AftercenterexitsTaiwan,rainfallincreaseduetostrongermonsoonTCinteraction. NotpositivefeedbackwithTCintensity(decreasedoverthe50
years) Inconsistentwithanthropogenicglobalwarmingtheories ConsistentwithnaturaldecadalvariabilityofMegaENSOand
AMV(Wangetal.2013) Consistentwithreductionofsteeringflowthatcausedthelongerduration
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ThankYou!
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Data JJA19582010,53years. Dailyrainstations:479(outof776)fromChinamainlandincludingHainanIsland,20fromTaiwan;95%complete.
Extremerainfalldefinedlocallyat90th percentile. EachraindayiseitherTCorMonsoon(nonTC). TCeventsidentifiedwithObjectiveSynopticAnalysisTechnique(OSAT,Ren etal., 2006),Influencerange5001100km.
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Hainan90th percentile
Total14.8%
Monsoon+35.1%
Underestimate
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19582009(26.57)
16
18
20
22
24
26
28
30
32
34
36
38
1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 2008
19582009(3.13)
2001
0
1
2
3
4
5
6
7
8
1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 2008
3422
25
()
Totalfrequency+