East Asian Climate Variability and Change(A Brief Review)

Huang-Hsiung Hsu
Laboratory for Climate Change Research
Research Center for Environmental Changes
Academia Sinica
Consortium for Climate Change Study(CCliCS/MOST)
Taiwan Climate Change Projection andInformation Platform (TCCIP/MOST)
DSWS, Tsukuba, October 2017

East Asian Winter Monsoon

ColdSurges

MJO

Subtropical High

Convectivesystems

courtesy of C.-P. Chang

Winter Climate Variability

Need to understand as part of global system

Regime Shift and Change in Dominant Modes
Mechanisms?

15%

CRU+Hadisst temperature 1941-2002 (JFM)

1988
12%

8%

1976?
Lo and Hsu 2011

Late 1980s Warming in East Asia
(associated with NAO/AO)
40 ° -70 ° N average•••(1988-1997) – (1978-1987)

30 ° -60 ° Naverage
Synchronousregime
shift occurred in the whole troposphere, on
and under ocean surface. What cause this?
A dominant hemispheric (global) pattern, which has not been wellunderstood?
Mutual enhancement through ocean-atmosphere teleconnection?

2017/10/12

shaded: temperature

contour: v-windarrow: u-w windLo, T.-T.

5

Global impacts of
the 1980s regime shift
Reid et al., 2015

Global Change Biology,
doi: 10.1111/gcb.13106
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China dust storm (decreased)
Global Tropical cyclone (increased)
CO2 land uptake (increased)
Antarctic sea ice/Baltic sea ice (d)NH spring snow (decreased)
Starting growing season (NH)Japan Sea T 50m (higher)
Japan cherry blossom (earlier)Japan Sea tuna catch (more)
Kuroshio current (stronger)
German grape ripening (earlier)North Sea phytoplankton (increased)
AO (negative  positive)…

EA warming can be simulated by SSTA forcing in the North AtlanticT2m

Observation

Simulation

After significant testAfter significant test

SLP

East Asia winter and Barents-Kara Sea SAT after
1979/80 (interannual time scale)“…severe winters (1979/80 – 2013/14) across East Asia are associated withanomalous warmth in the Barents–Kara Sea region …”(Kug et al. 2015, Nature Geoscience; similar in Mori et al. 2015; Kim and Son, 2016;
Petoukov and Semenov 2010, …)

SAT trend

Correlation (detrended)Positive Decadal Correlation:
NAO and Cold Surge Frequency
in Taiwan (correlation ~ -0.9)(Hong, Hsu, Chia, and Wu, 2008, GRL)

 Similar pattern in interannual
and interdecadal time scale Cause and Effect?
• NAO/AO like perturbation• Barents-Kara Sea SSTa
• others••Downstream impacts (of North Atlantic/Europe) on East Asian
climate/weather through Rossby wave-like propagation (waveguides)
How will this change in the warming future?

Combined effect of ENSO and AMO (Hao and He, 2017, J. Climate)enhanced

cancelledFuture Change Projection
HiRAM/GFDL: 1979-2008, 2075-2100 (RCP8.5)

Same ensemble SSTa used in MRI-AGCM20∗ Cube Sphere Globe (HiRAM)• Defined by intersects of great circles with equaldistance along 12 edges• Maximum local grid aspect ratio ~ 1.061• Maximum global grid aspect ratio ~ 1.414

Resolution:C384∆x = ~ 25 km

C192∆x = ~ 50 km

Projected Future Changes under RCP8.5

SLP(using 50/25-km HiRAM forced by ensemble SST changes)

Velocity Potential 200 hPa

U 200hPa

Streamfunction 200 hPa

850 hPa Stream Function

Precipitation

wetterdrier
wetter

Frontal Activity Change

Surface Temp.
HiRAM

Kitoh, A., 2017, JMSJ, 95, 7-33

CMIP5East Asian Summer Monsoon
Onset of phased
Monsoon rainbelt

SubtropicalHighSCS
MJO
Monsoon
Onset

Convectivesystems

courtesy of C.-P. Chang

Summer Climate Variability

Multiscale Nature; Convection-Circulation coupling

One of key factors affecting weather
and climate in the tropical WesternC.-H.Wu
North Pacific –Fluctuation of anticyclonic ridge (ACR)
and monsoon trough (MT)Interesting Contrast bet. Mean Circulationin North Atlantic/North Amer. and WNP/Asia- No monsoon trough in the NA/NA region
North Atlantic/
North American

Western NorthPacificTP10Topographic effect enhances summermonsoon flow (trough) and precipitation

TP01

observation

TP10TP12TP07

TP04

TP01

TP12 – TP10

TP10 – TP07

TP10 – TP04

TP10 – TP01

JJA (Precipitation, 850hPa winds)
C.-H. Wu

Tripolar Rainfall Pattern (CRU rainfall)(Pacific-Japan Pattern)

multiple (cross) time scales and mechanism
interannual
decadal+interannual

Linear trend

Nitta (1987) …
Pacific Japan Pattern

Enomoto et al. (2003) …
Silk Road Pattern• Wave-like perturbations forced by tropical WP or Tibetan heating• ENSO effect• Downstream propagation from Eurasian continent Can be easily induced by various perturbation and forcing

 Intrinsic mode? (Kosaka and Nakamura, Hsu et al., Hirota and Takahashi, …)

courtesy of Nakamura

Multiscale Interaction in the Tropical Western North Pacific
Hot Spots of A-O coupled Intraseasonal Oscillation (30-60 day) and TC
during May-October (Hsu, 2005, 2010)
OLR

SST

OLR propagation
C5 Typhoon
Occurrence collocated withintraseasonal
convection andTCHP variation

TCHP

Hsu and Weng, 2001,
J. Climate; Weng andHsu, 2017, GRL

1. Warm SST extends
southeastward.
2. Monsoon trough extends
southeastward.
3. 30-60day ISO and TC activity
shifts sourtheastward .

• ENSO → MT/ACR→ ISO and TC• Interannual → intraseasonal,
synoptic-meso scales 1. Warm SST retreatsnorthwestward.

2. Monsoon trough retreatsnorthwestward.
3. 30-60day ISO and TC activity
shifts northwestward.
鄒治華(Tsou)、徐邦琪(Hsu)TC contribution to Climate Variability
44-year mean

original

1958-2001 JJASO 850 hPa vorticity

TC-removed Hsu et al. 2008

Significant differences in long-term mean andinterannual variance (along TC tracks and more?) TC as part of climate variability

Interannual variance Climate models need to be able to realisticallysimulate TCs for a realistic simulation of climatevariability

Future Changes in TC Activity(HiRAM)

PresentTC Projection (C384)
similar in C192

End of Century

TCCounts

AMIP

RCP8.
5

NIO

5.7

6.1

WNP

35.8

20.4

ENP

15.9

21.1

ATL

8.6

6.0

SIO

18.2

14.2

SP

17.7

10.3

SA1.3

1.6

HiRAM C384

IPCC AR5vs.

MRI AGCM20km

NICAM (Yamada et al. 2017)

TS intensity distribution (JJASON)

Changes in ISO and TC genesis in the western North Pacific(Jul.-Sept.)

ISO Westerly phaseISO Easterly phase1085611071

JTWC

HiRAM

ISO/TC weakening
2075-2099
Minus
1979-2003(C.-H. Tsou)Changes in Atmospheric River Activity
May-JuneJuly-August

overall activity
increased

Shifting northwardand enhanced

Sept.-Oc.

Changes in Annual Precipitation Cycle
Projected by HiRAM
CMAP

AMIP

RCP85_ens—AMIP

mm/day
RCP85_C1 —AMIP%

RCP85_C2 —AMIP

Spring

2/15-5/15

Enhanced anticyclonic
circulation andmoisture transport
850hPa moisture transport
vector: uq,vq
shading: (uq2+vq2)1/2

850hPa moisture transport

Difference associated withthermodynamic part (increased q)

dynamic part (changes in u,v)

SpringCDD
CDD (unit: day)

Changes in CDD (unit: %)ExtremeRainfall(Pr99)
extreme e

Hatched regions: 5% significanceTyphoon Season
7/25-9/27
850hPa moisture transport
vector: uq,vq
shading: (uq2+vq2)1/2

850hPa moisture transport

Difference associated withthermodynamic part (increased q)

dynamic part (changes in u,v)

TyphoonSeason
CDD
CDD (unit: day)(unit: %)ExtremeRainfall(Pr99)

Hatched regions: 5% significanceThank you for Your Attention
Questions and Comments?

SSTA×2 simulation

Observation

Geopotential height

Geopotential height

Temperature

TemperatureRelative Contribution of SST Anomaly Pattern

El Nino-like effect suppressed by Indian warming effectExtreme Precipitation
Comparison between
MRI and HiRAM
HiRAM_C192
MRI(Kusunoki 2017)

South Asian Summer Monsoon

Somali Jet(X-Eq flow)

B of Bengal
MJOMonsoon
Onset
Qasi-2 week
active/break cycl

Convective
systems

courtesy of C.-P. Chang

Mean Climatology
Role of Topography

Sea Level Pressure
No Mountains

Topographic Effect- Boreal WinterMountains minus No Mountains

MountainsHeld (1983)

Effect of the Tibetan Plateau- Simulations with different heights

100% topography

10% topography

10% minus 100% topography

Warmer winterwith lower Tibet

Tseng, Wu, and Hsu

Low-level synoptic fluctuation propagating around the Tibetan Plateau
100% topography

Topography-varying experiments verify the steering effect of theTibet Plateau on circulation by exciting topographic Rossby waves.
10% topography

Hsu 1985

Simulation

Observation
GPCP(1997-2014)

1.2

TRMM(1998-2014)

1.0Topography enhances theseasonal northward marchfrom spring to summer.
- The higher, the stronger

0.8

0.6

0.4

C.-H. Wu

Effects of narrow mountains
in the Indochina Peninsula
on subseasonal evolution ofAsian summer monsoon- Proper representation of narrow
mountains is needed for realistic
simulations.
Annamese Mountains
Arakan Mountains

Wu, Hsu, and Chou 2014, JGR; Wu, Hsu, and Chou 2014, JGR

Simulation of late 1980s regime shiftModel : ECHAM5, T42L19
Anomaly Run SST Pattern : 1988-1997 minus 19781987, only over North Atlantic, amplitude x1, x2 and x4
Control Run = climatological SST
 10 (20) members from 01Jan-20Jan 1988 initial conditions

length of each simulation was 10 year and year 4-10 werecalculated.
Only focus on JFM

GPCP
Even precipitation?

CRU
After significant test

30-60day OLR var. and 850hPa streamline (JAS) composite

El Niño

La Niña

鄒治華(Tsou)、徐邦琪(Hsu)TC also modulated by ENSO
El NinoLa Nina

Multiple time scale nature
 Secular trend + Interdecadal-decadal variation + Interannual
variation + Seasonal evolution + Intraseasonal and subseasonal variation + ..
Example：
decadal vs. abrupt change (oscillation vs. shift)decadal+interannualIntraseasonal Oscillation (ISO, MJO, 季內震盪) vs. monsoon
onset
TC vs. ISO, interannual, decadal-interdecadal

Also related to diabatic heating over Tibet
Rainfall Composites (8 strong cases - 8 weak cases)

Tripole pattern

Hsu and Liu, GRL, 2003

Wet years
Tropical origin

Dry years
Extratropical origin

Hsu and Lin (J. Climate, 2007)

intrinsic mode of mean flow?
can be triggered by various forcing?

(Lu et al., 2006, JMSJ)Multiscale Interaction in the Tropical Western North Pacific
Hot Spots of Intraseasonal Oscillation (Hsu, 2005, 2010)

Hsu and Weng, 2001, J. Climate

Breeding and Play Ground of TCs

TS Frequency (JJASON)

Changes in typhoon (affecting Taiwan)
frequency and strength
Significantly
reduced innumber but
strengthened Rainfall within
200 and 100
km radiusincreased by
44 and 20 %Tsou et al., 2016, TAO

FIG. Distribution of TWCN TS track frequency (shaded, unit: numbers per 2.5olongitude/latitude per season period) in JUN.-NOV.

GPI Changes

ECHAM5 T213: AGCM (uncoupled) vs. AGCM-SIT (coupled)AGCM (daily OISST)
28 years

ECHAM5-SIT
20 years

NH74.5

77.1

WP

31.8

32.4

Western Pacific storm numbers
1098
7Num/year

65

AGCM

4

ECHAM-SIT

321016.5

19.5

22.5

25.5

28.5

31.5

34.5

Max Wind speed (m/s)

37.5

40.5

43.5

10Max voricity 850hPa

98
7
65

AGCM

4

ECHAM-SIT

32
10

18

34

50

66

1882

98

114

130

146162

Min mslp

1614
12
10

AGCM

8

ECHAM-SIT

64
20987.75

993.25998.751004.25

1009.75

1015.251020.75

1026.251031.75

1037.25

Similar response in another RCP8.5 warming simulation
using ECHAM5-SIT with different SST warming pattern (JJA)

W.-L. Tseng, June Chang

Comparison with other models (not resolving TCs)

ECAHM5-SIT (T213), TC resolving

 Different SSTAs produce similar response but not El Niño-like SSTA Relatively insensitive to regional structure of SSTA

Kitoh, A., 2017, JMSJ, 95, 7-33

Front frequency change

CMIP5 (RCP85-historical)

HiRAM(RCP8.5-historical) (NF-historical) (RCP8.5-NF)

AtmosphericRiver
Frequency(passed Taiwan)

HiRAMhistorical

HiRAMrcp85

Rcp85-historicalthermodynamic- dynamic response

Moisture flux&divergence
Composite difference(rcp85 minus historical)

AR frequency
Rcp85-historical

IVT strength probability density function

Spring Rainfall in Warmer climate
Mean yearly max
continous dry daychange

95% tile rain fall strength change

Dry day ratio change
Rain strength change