Benefits of Typho on from a Hong Kong Perspective Hilda Lam, M.H. Kok and Karen Shum Hong Kong Observatory Hong Kong, China ESCAP/WMO Typhoon Committee

Benefits of TyphoBenefits of Typhoon on

from a Hong Kong Perspectivefrom a Hong Kong Perspective

Hilda Lam, M.H. Kok and Karen Shum

Hong Kong Observatory

Hong Kong, China

ESCAP/WMO Typhoon Committee 5th Integrated WorkshopMacao, China, 6-10 September 2010

Contents

• Experience from other places

• Benefits of typhoons from a Hong Kong perspective– source of water– for relieving long and severe drought– Potential contribution to wind energy– cooling effect in summer

Benefits of Tropical Cyclones Benefits of Tropical Cyclones

Experience from other placesExperience from other places

Benefits of TCs in Hydrology

Rainfall from TCs provides important water resources in many places:

• In inland Australia, significant amount of total rainfall comes from TCs (Ryan, 1993).

• In China, “Ranaim”, “Haitang” and “Matsa” in 2004 replenished reservoirs and increased grain production and farmer’s income (Liu, 2006).

• In the United States, 9 major TCs in 1932-1963 terminated drought conditions over an area of 10,000 sq. miles or more (Sugg, 1968).

The estimated area where drought was terminated

Tracks of TCs that terminated drought in the US

Benefits of TCs in Fisheries

• TCs enhance the production of phytoplankton, the base of the ocean food chain

– Vertical mixing bring the nutrient-rich water in deep layer to ocean surface

– “Kai-Tak” in 2000 triggered an average 30-fold increase in surface chlorophyll-a concentration over the South China Sea

– (Lin et al., 2003)

Surface Chrorophyll-a satellite image composite

Before the arrival of Kai-tak

After the passage of Kai-takEnhancement of biological activities

Benefits of TCs in Fisheries

• Increases in the lobster population have been observed after rough sea and high tides generated by TCs (Sugg, 1968).

Role of TCs in Regulating Climate• Induce upper-ocean mixing (Korty et al., 2008)

– Stronger mixing of the tropical oceans can force the oceans’ meridianal heat flux to increase, which cools the tropical latitudes and warms the higher latitudes.

• Redistribute heat polewards and drives the thermohaline circulation (Emanuel, 2001; Sriver et al., 2007; Jansen et al., 2009).

Sea surface temperature after the passage of Hurricane Edouard in 1996 (Emanuel,2001)

Average cyclone-induced surface cooling of the upper ocean (Sriver et al., 2007)

Enhanced Wind Power Production by TCs

• High winds associated with TCs could enhance production of wind energy, especially for the wind farms in the coastal areas.

• Influence of TCs on the wind power generation in China– ~ 30% of landfalling TCs may cause damage to the wind

farms– ~ 55% of landfalling TCs with winds of less than Force

10 to wind farms are beneficial to the efficiency of the wind power production

– Song et al., 2006

From a Hong Kong From a Hong Kong perspectiveperspective

Hong Kong

• Size: ~1100 sq. km• Population:

– 7 million ( 2009)• GDP (2009)

– 1632 trillion– Services( 92%) – Industries( 8%) – Agriculture( 0.1%)

• Modern city with good infrastructure

TC casualties in HKMost devastating typhoons over HK• 1906 typhoon : 15 000 death• 1937 typhoon : 11 000 loss of lives

Ocean-going vessels in trouble

0

10

20

30

40

50

60

1960

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

Ocean-going vessels in trouble

Major TC

1962Wanda

1964Ruby

1971Rose

1979Hope

1983Ellen

Small craft sunk or wrecked; damaged

0

200

400

600

800

1000

1200

140019

60

1962

1964

1966

1968

1970

1972

1974

1976

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

2004

2006

2008

2010

Small craft sunk or wrecked Small craft damaged

Major TC

1962Wanda

1964Ruby

1971Rose 1979

Hope1983Ellen

1960Nancy

Damage caused by TC in Hong Kong

Damage in monetary terms (million HK$)

0

50

100

150

200

250

198

3

198

5

198

7

198

9

199

1

199

3

199

5

199

7

199

9

200

1

200

3

200

5

200

7

200

9

mill

ion

HK

$

Benefits of typhoons from a Benefits of typhoons from a Hong Kong perspectiveHong Kong perspective

Source of waterSource of water

Climatologically, TCs contribute ~30% rainfall in Hong Kong

0

500

1000

1500

2000

2500

3000

3500

400019

61

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

2006

2009

rain

fall

(m

m)

TC rainother rain

19878%1964

60%


for relieving long and for relieving long and severe droughtsevere drought

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7 8 9 101112 1 2 3 4 5 6 7 8 9 101112 1 2 3 4 5 6 7 8 9 101112

1962 (1741 mm) 1963 (901.1 mm) 1964 (2432.1 mm)

rain

fall

(mm

)

monthly rainfallrunning 12 month rain1961-1990 normal

Oi

va

Worst drought in Memory(Monthly rainfall 1962-1964)

Downpour of Viola as relief of severe drought

• 1962 was dry - 1741mm of rainfall (~ 20% below normal )• 1963 even drier only 901 mm of rainfall (~ 60% below)• By 2 May 1963 - water supply down to 3 hours/ day • By 16 May - forced to restrict water supply to 4 hours

every other day • By 1 June 1963 when reservoir storage dropped to 175

million gallon, ~1.7%of reservoir capacity, forced to restrict further to 4 hours of supply every 4 days

• Not until 27 May 1964 when passage of Typhoon Viola brought torrential rain (300.6 mm in 5 days ), the persistent drought was relieved

• Year long “4 hours every 4 days” measure terminated

Track of Typhoon Viola in May 1964

1963: driest year; water supply: 4 hours every 4 days - the long queue for fresh water

• Courtesy Hong Kong SAR Information Services Department

1963 Severe Water Rationing

• Source: Water Supplies Department


Enhancement ofEnhancement of

wind energy potentialwind energy potential

Wind energy Wind energy resource at a potential site is expressed in

mean wind power density (WPD), is defined as:

• watts per square meter (Wm-2)• average wind power available per unit area swept by a

wind turbine blade over a certain period (Janardan & Nelson, 1994)

• 10 min mean wind is used in the calculation of WPD below

WPD = (0.5)()( u3 ) (1)

where = the air density, and

u3 = the average of cube of the mean wind speed.

Wind power density in Hong Kong

• ≥ Class 3 utility-scale wind power applications, • ≥ Class 4 large-scale wind farms• areas with potential for large-scale wind farms in Hong Kong hilltops and offshore waters.

Wind power class

Wind power density (Wm-

2)

1 0-100

2 100-150

3 150-200

4 200-250

5 250-300

6 300-400

7 400-1000

Ratio of potential wind power density (WPD) during TC passage to the annual average

Cheung Chau-offshore

Tate’s Carin-hilltop

Tai Mo Shan-offshore

Waglan Island- hilltop

Average annual mean wind speed (m/s)

5.0 6.1 6.7 6.2

Annual mean WPD

(2000-2009) (Wm-2)

204 283 397 339

WPD (Wm-2) during TC* 475 627 923 782

Ratio: TC/annual 2.3 2.2 2.3 2.3

% time with usable wind speed (3~25m/s) during TC *

79% 82% 86% 84%

• Hilltops & offshore sites in HK selected with potential for large-scale wind farms* TC within 600 km of Hong Kong in 2007-2009: 69 days

1st Wind Turbine at Lamma Island, S of HK~5 yr effort by HK Electric, a local power co.policy & other constraints


cooling effect in summercooling effect in summer

TCs in 2007-2009 studied(within 600 km of HK)

No. of TC Name of TC

2007 5 Toraji, Pabuk, Sepat, Francisco, Peipah

2008 7 Neoguri, Fengshan, Kammuri, Nuri, Hagupit, Higos, Maysak

2009 9 Linfa,Nangka, Soudelor, TD July, Molave, Goni, Mujigae, Koppu, Parma

Total 21

Passage of Tropical Cyclones near Hong Kong (T1,T2 T1-2 mark the day)

x Hong Kong

r : 600kmT1

T1-2

T2

Data and methodology

• Use daily mean air temperature at the Observatory during the passage of TC (T1 to T2)

• Calculate deviation from the mean temperature for that day and sum for all TC

• Mean temp is the 5-day mean for 2000-2009• Normally include + 2 days before entering 600km

of HK to take account of possible subsidence ahead.

Temperature - Fengshen in 2008(within 600 km on 23-26 Jun)

T1 T2T1 T2T1 T2T1 T220

22

24

26

28

30

32

Fe

ng

she

n-2

Fe

ng

she

n-2

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008

2008 mean temp (deg. C)

round 5day 2000-2009 mean

Fengshen

Fengshen 00Z 25 June 2008

20

22

24

26

28

30

32

Ha

gu

pit-2

Ha

gu

pit-2

Ha

gu

pit

Ha

gu

pit

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008



T1 T2

T1-2

T1-1

20

22

24

26

28

30

32

Ha

gu

pit-2

Ha

gu

pit-2

Ha

gu

pit

Ha

gu

pit

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008



T1-2

20

22

24

26

28

30

32

Ha

gu

pit-2

Ha

gu

pit-2

Ha

gu

pit

Ha

gu

pit

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008



T1-2

20

22

24

26

28

30

32

Ha

gu

pit-2

Ha

gu

pit-2

Ha

gu

pit

Ha

gu

pit

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

9 9 9 9 9 9 9 9 9 9 9 9 9 9 9

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008



T1-2

Hagupit 2008 warming in preceding 2 days (21-22 Sep)

Air temperature anomaly of 21 Tropical cyclones

in 2007 -2009

TC days

(T1-2 to T2)

Total anomaly (oC)

Average anomaly (oC/day)

93 -16 -0.17

• T1-2 ~ T2 starts preceding 2 days & when TC within 600 km of Hong Kong or TC formation, whichever is later

• Anomaly with reference to 5-day mean 2000-2009

No. of TC with net cooling effect (T1-2~T2)

Number of TC with

-ve anomaly

% of TC

with

-ve anomaly

2000-2009 13/21 62%

Total No. TC 21

Days of T1-2, T1, T2, T2+1, T2+2, T2+3

x Hong Kong

r : 600kmT1

T1-2

T2

T2+1

T2+2

T2+3

Air temperature anomaly –extended to cover 3 days after T2r

Total anomaly (oC) days Average anomaly (oC/day)

Reference 2000-2009 2000-2009

T1-2 ~T2 -16 93 -0.17

T1-2 ~T2+1 -26.8 111 -0.24

T1-2 ~T2+2 -31.2 128 -0.24

T1-2 ~T2+3 -35.8 145 -0.25

• T1-2 ~ T2 starts preceding 2 days & when TC within 600 km of Hong Kong or TC formation, whichever is later

• 21 TCs within 600 km of HK in 2007-2009 spanning 93 days

Calculate the temperature deviations using different means

as reference

• 5-day mean 2000-2009

• 5-day mean 1971-2000

• 5-day mean 2007-2009

Temperature - Fengshen in 2008(within 600 km on 23-26 Jun)

20

22

24

26

28

30

32

Fe

ng

she

n-2

Fe

ng

she

n-2

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008

2008 mean temp (deg. C)71_2000 5d mean temp(deg. C)round 5day 2000-2009 meanround 5day 2007-2009 mean

T1 T220

22

24

26

28

30

32

Fe

ng

she

n-2

Fe

ng

she

n-2

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008


T1 T220

22

24

26

28

30

32

Fe

ng

she

n-2

Fe

ng

she

n-2

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

Fe

ng

she

n

13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6

2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008 2008


T1 T2T1 T2

Air temperature anomaly of all TCsunder various references

Total anomaly (oC) days Average anomaly (oC/day)

Reference 1971-2000

2000-2009

2007-2009

1971-2000

2000-2009

2007-2009

T1-2 ~T2 5 -16 -25.5 93 0.05 -0.17 -0.27

T1-2 ~T2+1 0.6 -26.8 -32.1 111 0.01 -0.24 -0.29

T1-2 ~T2+2 2.1 -31.2 -31.7 128 0.02 -0.24 -0.25

T1-2 ~T2+3 3.7 -35.8 -32.2 145 0.03 -0.25 -0.22

• In a changing climate, following 5 day mean compiled for inter-comparison– 1971-2000 of 30 years– 2000-2009 of 10 years– 2007-2009 of 3 years

Increased annual impact of electricity consumption

per degree rise of temperature

1.72

3.26

5.5y = 1.89x - 0.2867

R2 = 0.9887

0

1

2

3

4

5

6

0 1 2 3 4

HK$ billion

(HK$線性billion)

• Source :Fung (2004)deg

Impact in Billion HK$

Estimated economic saving in electricity consumption (HK$)

Temp. increase by (°C)

Annual

Monthly For 93 TC days in

3 years

savings in 07-09 (billion)

1 1,720,000,000 143,333,333 438,246,575 -

-0.17 -292,400,000 -24,366,667 -74,501,918 -0.07

-0.27 -464,400,000 -38,700,000 -118,326,575 -0.12

* based on electricity consumption in 2002 (Fung 2004)

~HK$20m per year

Some TC with net cooling effect (T1-2~T2, total anomaly non -ve)

TC Significant subsidence ahead

Compact convection

Not in proximity

Tracking to the E of HK

Hagupit 2008

√

Goni 2009 √ √

Linfa 2009 √ √

Soudelor 2009

√

TD Jul 2009 √ √ √

• +ve anomaly of Linfa and TD Jul in T1-2~T2 everyday

Summary –Typhoon Benefits in Hong Kong

– Source of water

– Relieve prolonged

– Cooling and moderating hot summertime

– Potential wind energy

~ Thank you ~

Documents

Benefits of Typho on from a Hong Kong Perspective Hilda Lam, M.H. Kok and Karen Shum Hong Kong Observatory Hong Kong, China ESCAP/WMO Typhoon Committee