chapter 3 variable weather and changing climate a continuing challenge? 1

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CHAPTER 3

VARIABLE WEATHER AND CHANGING CLIMATE

A Continuing Challenge?

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August 2005

Costliest disaster: USD $81 billion

One of the deadliest: 1,836 people died

6th strongest in Atlantic history

CHECK-IN: Hurricane Katrina

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In this chapter you will explore three key questions:

1. Why do different places experience different weather and climate?

2. What is happening to the Earth’s climate?

3. Is the weather becoming more extreme?

CHAPTER 3 VARIABLE WEATHER AND CHANGING CLIMATEA Continuing Challenge?

Gateway 3: Is the weather becoming more extreme?a. What are the characteristics of tropical cyclones?

b. Where are tropical cyclones found?

c. What are the hazards associated with tropical cyclones?

d. What are the impacts of tropical cyclones?

e. How do people respond to tropical cyclones?

CHAPTER 3 VARIABLE WEATHER AND CHANGING CLIMATE

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Tropical Cyclone

Weather system created over warm oceans in the tropics.

Size ranges from 150 km to 1,000 km in diameter.

a. What are the characteristics of tropical cyclones?

Hurricane Catarina over Brazil in 2004 as seen from space

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• Tropical Cyclones have two key characteristics:- Strong winds

Low central pressure causes winds to spiral inwards and upwards at high speeds of 119 km/h. The huge difference in pressures creates strong winds.

- Low central pressure An area of low central pressure is formed in the middle of the

tropical cyclone (eye). The eye is characterised by calm conditions and the absence of clouds.


KQ3: Is the weather becoming more extreme?a. What are the characteristics of tropical cyclones?





f. Example: Tropical Cyclone Yasi



• Latitude 8° and 15° N and S of Equator.• Conditions needed:

- High ocean surface temperatures of above 26.5°C.- Coriolis effect (deflection of winds, creating spiraling motion)

In northern hemisphere, tropical cyclones move in anti- clockwise direction

In southern hemisphere, tropical cyclones move in clockwise direction

• Tropical cyclones are also known as hurricanes and typhoons.


• Storm surges

• Wind damage

• Torrential rain

Damage from Cyclone Sidr which hit Bangladesh in 2007

Storm surge• What is a storm surge?Sudden rise of sea level in which water is piled up against a coastline beyond normal conditions at high tide.

• How is it formed?Low eye pressure causes sea Level to rise; strong winds push water towards the coast and create huge waves.

Storm surge

• Greatest destruction to coastal areas.- Loss in property and lives- Vessels swept and stranged

inland

• Eg. Hurricane Ike (2008)- Storm surge was 4–6 metres

above normal tide level- Property damage: US$ 24.9b

Damage from Hurricane Ike

Wind damage

• Hurricane Camille recorded the highest wind speed at 305km/hour!– Causes huge damage:• Destroy infrastructure and buildings

• Injure people

• Causes loose debris to fly and hit people/buildings

Torrential rain

•Flooding- Large amount of rainfall causes flooding inland and also

cause rivers to overflow.- Eg. Hurricane Isabel in 2003 flooded areas 120 times the

size of Singapore in USA causing damages of more than US$2.23billion.

•Landslide- Excess water in soil will destabilise slopes.- Eg. Typhoon Megi created landslides in Taiwan, destroying

buildings and roads.


• Physical

• Economic

• Social Damage from Cyclone Sidr

Physical impacts• Damage to

infrastructure– Houses and

buildings Unable to live

in them– Roads and

bridges Unable to

transport emergency supplies such as food, medicine, water.

Road networks and houses destroyed by hurricane Katrina

Economic impacts

• Cost of repairs- Fixing or renovating buildings

• Cost of damage- Damage to crops and buildings/ infrastructure

• Loss of income- Income lost due to inability to work during period of

tropical cyclone or damaged crops

Economic impacts

• US$4 billion needed to repair infrastructure and provide humanitarian aid (eg medicine, water filter, tents etc) after Typhoon Nargis in Myanmar in 2008 .

• Economic losses for countries affected by typhoons amount to US$26 billion annually, projected to increase to US$55 billion by 2100.

Social impacts

• Disrupt water supply– Burst sewage pipes will contaminate water.– Damage to infrastructure disrupts supply of fresh water to

people.

• Spreading of diseases – Stagnant water allows mosquitoes to breed, aiding the

spread of malaria and dengue.– Dirty water also results in water-borne diseases such as

cholera and typhoid fever.

• Displacement of people from homes– People lose their homes due to rising flood waters.


• Emergency action- Evacuation of people- Provision of emergency aid

• Mitigation measures: strategies to reduce or avoid the impact of a hazard- Prediction and warning- Land use Control- Floodplain management- Reducing vulnerability of Infrastructure

Emergency action• Immediate action in

response to a situation that poses an immediate risk to health, life, property or environment.- Evacuation of people:

Community cyclone shelters are built near homes of people to protect them from tropical cyclones and provide them a place to live temporarily.

People injured from Hurricane Katrina being evacuated

• Provision of emergency aid by the government, neighbouring countries and non-governmental organisations- Provision of

clothes, shelter, food, medicine

- Repair damage to infrastructure

Emergency actionTents set up by the Federal Emergency Management Agency after Hurricane Andrew in 1992

Mitigation measures: Prediction and warning

• Prediction: - Analyse long-term climate records

Establish pattern and severity of past cyclones to predict future cyclones.

- Analyse path of current cyclone through computer modelling Establish the likely path the cyclone will take based on

weather information- However these methods are limited

• Warning- Allows people to evacuate in time

Japan and America has advanced prediction and warning systems, which allows people to evacuate way before tropical cyclones arrive

Mitigation measures: Land use control

• Regulates the use of land by placing restrictions on how the land can be used- Developers pay higher taxes for use of land- Land which is vulnerable to tropical cyclones only used for

recreation- Land converted into protected areas.

Mitigation measures: Land use Control

• Limitations to land use control- Authorities need to be able to enforce the rules which

requires time and manpower- Residents along coastlines often reluctant to move out;

government needs to buy back the land to turn the land into recreational areas, which is costly

Mitigation measures: Floodplain management

• Floodplain management: masterplan to reduce the flood damage potential

• Mapping risk levels of areas allows planners to: - Ensure new developments on floodplains are not prone to

flooding- Reduce flood damage potential in already developed

floodplains- Ensure people are able to evacuated quickly during floods.

Mitigation measures: Reducing vulnerability of infrastructure

• Infrastructure needs to be able to withstand the impacts of tropical cyclones- Wind and water resistant buildings- Inspect river embankments and coastal dikes for wear and

tear- Locate utility lines underground

• Wind and water resistant buildings- Galvanised steel hurricane ties

Nailed to roof to secure it prevent it from being blown off during typhoons.

- Secondary water resistant layer Added to roof to prevent leaking should roofs be blown off

• Effectiveness seen in when houses with these improvements in Florida, USA, survived Hurricane Wilma with little damage in 2005.


• Protective barriers: river embankments and coastal dykes.– Prevent water from overflowing river banks and also prevent

surging waves from moving inland

– However, regular inspection and expensive maintenance are needed for these measures to be effective


f. Example: Tropical Cyclone Yasi When and where did Tropical Cyclone Yasi occur?• One of most

significant tropical cyclones in the Pacific Ocean


What were the weather conditions and the damages inflicted by Tropical Cyclone Yasi?• Category 5 tropical cyclone on Saffir-Simpson

Hurricane Scale- Meaning wind speeds of > 200km/h

Yasi hit 290km/h

• Caused serious damage to the country (cost of damages up to US$3.5 billion)

f. Example: Tropical Cyclone Yasi What were the weather conditions and the damages inflicted by Tropical Cyclone Yasi?• Heavy rainfall

- 200–300 mm in 24 hours (similar to what Singapore receives in its rainiest month, December!)

• Widespread flooding from storm surges- Significant storm surge of 5.5 m in Cardwell

• Power supply cut- Took 1 month to restore all power due to the sheer number

affected (170,000 homes)

• Crops destroyed - Banana and cane fields, wiped out 75% of Australia’s crop

production.

f. Example: Tropical Cyclone Yasi How effective were the measures adopted to mitigate the impact of Tropical Cyclone Yasi?• Despite being a category 5 storm, death toll was low due to high

level of disaster risk awareness and preparedness.

• Increasing number of tropical cyclones and increasing number with category 4 or 5 intensity storms.- Linked to rise in global sea surface temperatures which is a

condition needed for cyclone formation

• Despite improvements in prediction, tracking and preparation for cyclones, damage is always unavoidable.

• As favourable conditions for tropical cyclones will always exist, they are a challenge we always need to be prepared for.


chapter 3 variable weather and changing climate a continuing challenge? 1

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