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%
Benefits of typhoons from a Benefits of typhoons from a Hong Kong perspectiveHong Kong perspective
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
Benefits of typhoons from a Benefits of typhoons from a Hong Kong perspectiveHong Kong perspective
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
Benefits of typhoons from a Benefits of typhoons from a Hong Kong perspectiveHong Kong perspective
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
2008 mean temp (deg. C)
round 5day 2000-2009 mean
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
2008 mean temp (deg. C)
round 5day 2000-2009 mean
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
2008 mean temp (deg. C)
round 5day 2000-2009 mean
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
2008 mean temp (deg. C)
round 5day 2000-2009 mean
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
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
2008 mean temp (deg. C)71_2000 5d mean temp(deg. C)round 5day 2000-2009 meanround 5day 2007-2009 mean
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 ~