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

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.

Introduction

GlobalWarming Increasingvaporcapacityincreasingrainintensityandextremerainfall.

ClimatemodelssimulatedincreasingtrendofextremerainfallsimulatedoverNHlandarea;observedoverEurope&N.America,butunclearoverAsianmonsoonregion.

VerylargeincreasingtrendofextremerainfallreportedinTaiwansince1998,attributiontoglobalwarmingisthesubjectofongoingdebate(increasingvaporandpositivefeedback?)

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.

RainfallinEastAsiaSummerMonsoon

ExtremerainfallcontributedbybothmonsoonandTropicalCyclones(TCs)

TCsinfluencedbytropicalwesternNorthPacificconditions(upstreamofEastAsianlandmass)

Extremerainfallinfluencedbyexternalfactorsnotpartoflocalthermodynamicconditions

Typhoonrainfalllineartrends

Intensity AmountFrequency

PercentageofTCrainfallinTotalRainfall

PercentageofTCrainfallinExtremeRainfall(90th Percentile)

NEC

YV

SC

HN

Taiwan90th percentile

Total19.5%

Monsoon10.9%

Overestimate~79%

Total46.2%

Monsoon12.2%

Overestimate

(byamount)

(byevents)

SomostofChinaSummerMonsoonAreathetrendofextremerainfallwasunderestimated,becauseoflessTCrainfall.IfTCinfluenceisremoved,extremerainfalltrendwillbemoreclear.

Taiwanisanexception. WhatcauseTaiwanstyphoonextremerainfallincrease?

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

13

PreLandfall

OverLand

EXit

TyphoonTrackPhases

PReLandfall

2008

2004

2009

20052007

OverLand

EXit

PhaseTrack Type

PR OL EX

N 1960 2132 1458C 1305 1558 1467S 1033 812 572

Table2:The12hourrainfallintensity(mm)forthethreetracktypesduringthethreephases.

1.Terraineffectdominates2.Afterexit,SWmonsooninteractionimportant

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+

Composite Rainfall

(Hsu,Kuo andFovell 2013,JAS)

Nduration+

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?

HugeincreaseofTCrainsignifiesglobalwarming/climatechangeeffects?

PrelandfallandOverland,theincreaseisduetolongerdurationandslightchangeoftracks.

Resultofstrongcontrolbyterraineffect(trackchangeismesoscale)

AftercenterexitsTaiwan,increaseduetostrongermonsoonTCinteraction.

Linktoglobalclimatechangepossible:(butnotTCintensity)

GlobalWarming?orNaturalVariability?

GlobalWarmingorNaturalVariability?

Strengthening ofNHsummermonsoonandtropicalcirculationsconsistentwithslowersteeringflowofTaiwanTCsandenhancedmonsooninteractionafterTCleavesTaiwan.

GWpredictsweakening oftropicalcirculations.

(Wang,B.etal.2013,PNAS)

Conclusions IncreasingextremerainfalltrendinAsianmonsoonlandarea

maskedbydecreasingTCrainfallactivity.Taiwanisanexception. PrelandfallandOverland,TCrainfallincreaseisduetolonger

durationandslight(mesoscale)changeoftracks. Localterraineffectcontributestoanimpressionofclimatechange,

yetitstronglyconstraintstherainintensityandmasksbroadscaleclimatechange.

AftercenterexitsTaiwan,rainfallincreaseduetostrongermonsoonTCinteraction. NotpositivefeedbackwithTCintensity(decreasedoverthe50

years) Inconsistentwithanthropogenicglobalwarmingtheories ConsistentwithnaturaldecadalvariabilityofMegaENSOand

AMV(Wangetal.2013) Consistentwithreductionofsteeringflowthatcausedthelongerduration

ThankYou!

Data JJA19582010,53years. Dailyrainstations:479(outof776)fromChinamainlandincludingHainanIsland,20fromTaiwan;95%complete.

Extremerainfalldefinedlocallyat90th percentile. EachraindayiseitherTCorMonsoon(nonTC). TCeventsidentifiedwithObjectiveSynopticAnalysisTechnique(OSAT,Ren etal., 2006),Influencerange5001100km.

Hainan90th percentile

Total14.8%

Monsoon+35.1%

Underestimate

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+