Effects of Global Warming, El Nino and other Climate Variations on Typhoon Activity in Asia

Johnny ChanGuy Carpenter Asia-Pacific Climate Impact Centre

School of Energy and Environment

City University of Hong Kong

1Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Outline

Crash course on global warming, El Niño and the Pacific Decadal Oscillation

Crash course on typhoons

Possible effects on typhoon activity

Summary

2Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Global warming – current temperatures

3Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Global warming – future projections

4Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Global warming – temperatures in the late 21st century

5Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Global warming – rainfall in the late 21st century

WINTER

SUMMER

6Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño/Southern Oscillation (ENSO)

7Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño/Southern Oscillation (ENSO)

8Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño/Southern Oscillation (ENSO)

NINO1+2NINO3NINO4 NINO3.4

9Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño/Southern Oscillation (ENSO)

10Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño Modoki

11Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño – Southern Oscillation

12Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño/Southern Oscillation (ENSO)

13Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Pacific Decadal Oscillation

warm phase cold phase

14Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Pacific Decadal Oscillation – PDO index

warm warmcold cold cold

15Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Tropical Cyclones – Structure

16Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

1.sea-surface temperature > 26.5oC - to provide

enough moisture and thermal buoyancy for deep

convection to occur

2.conditionally unstable atmosphere - to allow

moist air to rise through a deep layer of the

atmosphere

3.moist lower to mid troposphere - so that the

condensed water will not evaporate and will

continue its ascent

Tropical Cyclone formation: Thermodynamic Conditions

17Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

May-Oct

Nov-Apr

Tropical Cyclone formation: Ocean surface temperature

18Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

1. strong anticlockwise rotation near the

ocean surface and clockwise rotation in the

higher atmosphere - to provide the

necessary rotation in the low levels and

allow outflow in the upper levels

2. small vertical wind shear near the centre of

the disturbance - so that the convection

will not be sheared off

Tropical Cyclone formation: Dynamic Conditions

19Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Tropical Cyclone formation: East-west Winds and Shear

flow near

ocean surface

flow in the

upper

atmosphere

20Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Annual Number of TCs and intense TCs in WNPAnnual number of TSs and Cat45 TCs over the WNP

15

20

25

30

35

40

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

0

2

4

6

8

10

12

14

TS

10-yr filtered TS

Cat45

10-yr filtered Cat45

21Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

ACE vs. May-Nov SSTA (5-30oN, 120-180oE)

-1.5

-1

-0.5

0

0.5

1

1.5

1964 1969 1974 1979 1984 1989 1994 1999

ACE

SSTA

correlation = 0.23

22Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

ACE vs. VORT, SHEAR and MSE

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

ACE

VORT EOF1

SHEAR EOF1

MSE EOF2

0.580.72 0.67

23Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Variations of Landfall in Each Area at Various Oscillation PeriodsSTC

-3

-2

-1

0

1

2

3

4

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year

Standa

rdized

anoma

lies

-1.5

-1

-0.5

0

0.5

1

1.5

2

Standardized anomalies

original

2-8 yr

8-16 yr

16-32 yr

sta

nd

ard

ize

d a

no

ma

lie

ss

tan

da

rdiz

ed

an

om

alie

s

MTC

-3

-2

-1

0

1

2

3

4

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year

Stand

ardize

d ano

malies

-1.5

-1

-0.5

0

0.5

1

1.5

2

Standardized anomalies

original

2-8 yr

8-16 yr

16-32 yr

sta

nd

ard

ize

d a

no

ma

lies

sta

nd

ard

ize

d a

no

ma

lies

sta

nd

ard

ize

d a

no

ma

lie

ss

tan

da

rdiz

ed

an

om

ali

es

South China, Philippines and

Vietnam

East China

Japan/Korea

24Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño effects on tropical cyclone activity

Year before

El Niño

El Niño Year

Year after

El Niño

25Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

La Niña effects on tropical cyclone activity

Year before

La Niña

La Niña Year

Year after

La Niña

26Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño effects on tropical cyclone activity

27Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño effects on tropical cyclone activity

28Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

July-Dec Mean Life Span (Days)El Niño effects on tropical cyclone activity

29Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño effects on tropical cyclone intensityIntensity vs. Nino3.4 SST

30Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

El Niño effects on tropical cyclone intensityTyphoon Days vs. Nino3.4 SST

31Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

PDO effects on tropical cyclone intensity

32Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Summary

Global warming does not cause changes in

typhoon activity (frequency of occurrence,

intensity, landfall locations) in Asia.

El Niño has a significant effect on typhoon

activity through modifications of the

atmospheric flow patterns that

subsequently lead to changes in location

of formation, and hence frequency of

occurrence, intensity and locations of

landfall.

33Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Summary

Effects of the Pacific Decadal Oscillation

apparently either collaborates with or

modifies those of El Niño on a decadal or

longer time scales. However, more

research is necessary.

34Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Conclusion and take-home message

In assessing typhoon risk on an annual

time scale, the most important factor is El

Niño. Better predictions of typhoon activity

come from better predictions of the

occurrence of El Niño.

On longer time scales such as decades,

other climate oscillations such as the

Pacific Decadal Oscillation need to be

considered. More research is necessary.

35Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Conclusion and take-home message

The effect of global warming on typhoon

activity is not obvious unless it can be

shown that global warming will lead to

changes in the frequency of occurrence of

El Niño or other climate oscillations. The

simple idea of an increase in ocean

temperature due to global warming will

enhance typhoon activity is incorrect.