Weather And Climate

Question 1

Weather

Answer 1

Condition of the atmosphere at a particular place and time

Question 2

Climate

Answer 2

Average condition of the atmosphere of a specific place over a long period of time, usually over 30years

Question 3

Latitude affecting temperature

Answer 3

Latitude is the distance of any point on the earth measuring from the North or South of the Equator. Latitudes are imaginary horizontal lines running from east to west around the earth and are measured in degrees. The temperature differs between places at lower latitudes and higher latitudes because the sun’s rays strike various parts of the world at different angles. At lower latitudes, the sun’s rays hit the earth’s surface at a higher angle of incidence, causing the heat to be concentrated on a small area, resulting in higher temperatures. At higher latitudes, the sun’s rays hit the earth’s surface at a lower angle of incidence, causing the heat to be spread out over a larger area, resulting in lower temperatures.

Question 4

Altitude affecting temperature

Answer 4

Altitude is the height of a place in relation to the sea level. When altitude increases, the temperature decreases. The heat from the sun passes through the atmosphere and hits the earth’s surface in the form of shortwave radiation. The higher up you are, the further you are from the surface of the earth that is heated by the sun. Therefore, temperature decreases with increasing altitude. Longwave radiation that is emitted by the earth is absorbed by greenhouse gases such as CO2 in the atmosphere, trapping the heat and warming the earth. Air is less dense at higher altitudes. Dense air is able to absorb more heat from longwave radiation from the earths surface , resulting in higher temperatures. Less dense air has less ability to absorb heat, causing lower temperatures.

Question 5

Maritime effect

Answer 5

Maritime effect is the effect that large ocean bodies have on the climate of coastal areas, resulting in a lower annual temperature range.

During summer, the air over the sea is cooler than the air over the land, as the land heats up faster than the sea. The cooler air over the sea helps to lower the temperature of the area, resulting in cooler summers.

During winter, the air over the sea is higher than the air over the land, as the land cools down faster than the sea. The warmer air over the sea helps increase the temperature of the area, resulting in warmer winters.

Question 6

Continental effect

Answer 6

Inland areas are further away from the sea, so the temperature in these areas is not influenced by the sea. As the land heats up during summer and cools down faster during winter, this causes the inland areas to experience warmer summers and cooler winters with a large annual temperature range than coastal areas.

Question 7

Cloud Cover

Answer 7

Cloud clover refers to the extent of the sky that is covered by clouds. The amount of cloud cover can affect the temperatures in the day and at night in a place. When there is more cloud cover, there will be a smaller difference between day and night temperatures, so the diurnal temperature range is smaller.
Clouds present :
During the day, clouds reflect a large amount of the sun’s energy back to space, so they reduce the amount of the sun’s energy from reaching the earth’s surface. Consequently, the earth’s surface is not heated up excessively and causes the earth’s surface to have a cooler temperature in the day when clouds are present. During the night, clouds absorb heat radiated from the earth’s surface and prevent it from escaping into space, so they warm up the air near the earth’s surface. This causes the earth’s surface to have a warmer temperature in the night when clouds are present. As a result, the different in the day and night temperature is smaller with the presence of cloud clover.
Clouds absent :
During the day, most of the sun’s energy can reach the earth’s surface as there are no clouds to reflect it back into space, so the earth’s surface heats up quickly and the air near the earth’s surface is warmer. This causes the earth’s surface to have a warmer temperature in the day when clouds are absent. During the night, more heat radiated from the earth’s surface can escape into space because there are no clouds to absorb it, so the air near the earth’s surface is cooler at night. This causes the earth’s surface to have cooler temperature in the night when clouds are absent. As a result, the different in day and night temperature is larger in the absence of cloud clover.

Question 8

Relative Humidity

Answer 8

The maximum amount of water vapour that warm air can hold is greater than cool air because air expands in warmer temperature. Therefore, when temperature increases, relative humidity decreases, assuming that the amount of water vapour in the air remains the same. Saturation occurs when the maximum amount of water vapour that the air can hold is reached. The temperature at which saturation occurs is called the dew point temperature. Water vapour is formed from the evaporation of water. Therefore, more evaporation will lead to more water vapour. Since evaporation is the result of the sun’s energy on water bodies, places with higher temperature and water bodies, will have more water vapour in the air. In addition, vegetation also give off water vapour in the process of transpiration. This is why the reservoirs in Singapore have so many trees planted around them.

Question 9

Clouds

Answer 9

Evaporation caused by the warm earth’s surface and transpiration by plants result in water vapour in the air. When the water vapour rises, it starts to cool. As water vapour cools to its dew point temperature, it condenses on any tiny particles present in the air such as dust. These tiny particles are known as condensation nuclei. The water droplets in the air will collide with each other to form large water droplets called coalescence, leading to the formation of clouds. The large water droplets eventually fall to the earth’s surface as precipitation.

Question 10

Relief Rain

Answer 10

When air passes over the sea, it picks up moisture before reaching the coast. When the moist air rises up the windward side of the mountain, it is forced to cool. When the air cools to dew point temperature, condensation occurs and clouds form. When the water droplets become large and heavy enough on the windward side of the mountain, they fall as relief rain. Relief rain usually makes the leeward side of the mountain become dry because most of the moisture would have fallen on the windward side.

Question 10

Convectional Rain

Answer 10

It is common in places experiencing large amounts of sunlight such as in the tropics. It brings intense rainfall over an area and is often associated with lightning and thunder and generally lasts only a short tie. When the earth’s surface is heated excessively, the warm surface heats up the air around it. The air becomes unstable as it expands and rises. As the air rises, its temperature starts to decrease. When the rising air cools to dew point temperature, condensation occurs and results in the formation of clouds. The water droplets in the clouds fall to the ground as rain when they become large and heavy enough.

Question 11

Air pressure

Answer 11

Air pressure is the force exerted on a unit area of the earth’s surface by the weight of a column of air above it. At high altitude, air becomes less dense because gravity pulls air molecules towards the earth’s surface. Hence, air pressure is higher at sea level at lower altitude and air pressure is lower at a higher altitude.

Question 12

Wind

Answer 12

Winds are the movement of air from an area of high pressure to an area of low pressure.

Question 13

Land and Sea breeze

Answer 13

During the night, the land loses heat faster than the sea, so the land has a lower temperature than the sea. As the cool air above the land sinks, the air pressure on the land becomes high. The sea loses heat slower than the land, so it has a higher temperature and lower air pressure than the land. The pressure gradient is created between the land and the sea, so air moves from the land of high pressure to the sea of low pressure to form a land breeze.
During the day, the land absorbs heat faster than the sea, so it has a higher temperature than the sea. As warm air above the land rises, the air pressure on the land becomes low. The sea absorbs heat slower than the land, so it has a lower temperature and a higher air pressure than the land. The pressure gradient is created between the land and the sea, so air moves from the sea of high pressure to the land of low pressure to form a sea breeze.

Question 14

Coriolis Effect

Answer 14

The Coriolis effect is the force produced by the earth’s rotation. It is the strongest near the poles, weak in the tropics and negligible at the Equator. In the Northern hemisphere, it deflects winds to the right. In the Southern hemisphere, it deflects winds to the left.

Question 15

Southwest monsoon

Answer 15

The southwest monsson takes place between June and September, when it is summer in the northern hemisphere. The air over Central Asia heats up, expands and rises, forming a region of low pressure over the sea. During the same period, the southern hemisphere is experiencing winter. The low temperature causes the air to be cold and dense, exerting a greater force on the earth’s surface and resulting in an area of high pressure over Australia. Due to the difference in pressure between Central Asia and Australia, air from Australia moves to the Indian sub-continent and Central Asia as the southeast monsoon winds. As the winds cross the Equator, the Coriolis effect deflects the winds to the right. These winds become the southwest monsoon winds and warm up as they head for Central Asia. The warm air picks up moisture as it travels over the Indian Ocean and brings heavy rain to the Indian sub-continent.

Question 16

Northeast monsoon

Answer 16

The northeast monsoon takes place between October and February, when it is summer in the southern hemisphere and an area of low pressure forms over Australia. During the same period, the northern hemisphere is experiencing winter. An area of high pressure develops over the Indian sub-continent and Central Asia. Due to the different in pressure between the northern and southern hemispheres, air moves from the Indian sub-continent and Central Asia to Australia as the northeast monsoon winds. These winds are generally dry and cold as they blow across col land. As the winds cross the Equator, the Coriolis effect deflects the winds to the left. These winds become the northwest monsoon winds and warm up as they head for Australia. The warm air picks up moisture as it travels over the Indian Ocean and brings heavy rain to Australia.

Question 17

Equatorial Climate

Answer 17

1. Located between 10 degrees north and south of the equator.
2. High mean annual temperatures of about 27 degrees celsius
3. Small annual temperature range of around 2 degrees celsius
4. High relative humidity of over 80% throughout the year.
5. High total annual rainfall of more than 2000mm.
6. Constant rainfall throughout the year.

Question 18

Monsoon Climate

Answer 18

1. Located between 5 -25 degrees north and south of the equator.
2. High mean annual temperatures of about 28 degrees celsius
3. Small annual temperature range of around 3 - 4 degrees celsius
4. High total annual rainfall of around 2000mm.
5. Distinct wet and dry season depending on the monsoon winds.

Question 19

Cool Temperate

Answer 19

1. Located at coastal areas between 40 - 60 degrees north and south of the equator.
2. Low to moderate mean annual temperature ranging from -3 to 22 degrees celsius
3. Large annual temperature range of around 21 degrees celsius
4. Low total annual rainfall of 300 - 900mm.
5. No distinct wet or dry seasons
6. Experiences the four seasons, spring, summer, autumn, winter.

Question 20

Global climate change

Answer 20

The variation in the global climate or climatic patterns in the long term

Question 21

Greenhouse effect

Answer 21

Incoming shortwave radiation passes through the greenhouse gases found in the atmosphere. Some shortwave radiation is reflected by the earth and the atmosphere. Most shortwave radiation is absorbed by the earth’s surface which then heats up as a result. The warmed surface of the earth emits longwave radiation to the atmosphere. Some of the longwave radiation is absorbed by greenhouse gases, warming the atmosphere, while some of the longwave radiation escapes to space. Some greenhouse gases are Carbon dioxide, Methane, Nitrous Oxide, Ozone and water vapour.

Question 22

Enhanced greenhouse effect

Answer 22

Incoming shortwave radiation passes through the greenhouse gases found in the atmosphere. Some shortwave radiation is reflected by the earth and the atmosphere. Most shortwave radiation is absorbed by the earth’s surface which then heats up as a result. The warmed surface of the earth emits longwave radiation to the atmosphere. Human activities are increasing the amount of greenhouse gases released into the atmosphere. The increased concentration of greenhouse gases in the atmosphere, absorbs even more heat, leading to a rise in global temperatures. This is known as the enhanced greenhouse effect.

Question 23

Variations in Solar Output

Answer 23

When the magnetic field of the sun changes, it affects the amount of its solar radiation reaching the earth. Sunspots appear as dark spots and are the cooler regions on the sun’s surface. The number of sunspots increases during the periods of intense solar magnetic activity. When the number of sunspots increases, solar radiation becomes higher as the areas surrounding the sunspots release more energy that compensate for the lower temperatures of the sunspot areas. The rising and falling in the number of sunspots occurs in a cycle which lasts about 11 years and linked to the earth’s cycle of high and low global temperature. In 2000, the peak in the number of sunspots coincided with high solar activity. Global temperatures increased during this period. In 2008, the minimum solar activity cycle coincided with lower global temperature compared to the past 20 years.

Question 24

Volcanic Eruptions

Answer 24

A volcanic eruption can release large amounts of carbon dioxide, water vapour, sulfur dioxide, dust and ash into the atmosphere. Sulfur dioxide reacts with water to form sulfur-based particles in the atmosphere. The sulfur-based particles, ash and dust are able to reflect solar energy back into the space and results in the cooling influence on regional and global temperatures. Volcanic eruptions only affect the earth’s climate temporarily as the global cooling effect will stop once the volcanic dust and ash settle. When Mount Pinatubo in the Philippines erupted in 1991, it released 17 million tonnes of sulfur dioxide into the atmosphere. This gas formed a large amount of sulfur-based particles to reflect solar energy back into space. As a result, the temperature in the northern hemisphere was lowered by 0.6*C for about 2 years.

Question 25

Deforestation

Answer 25

Deforestation is the loss of forests due to the removal or clearance of trees in forested areas. Trees are felled for wood to make products such as paper and building materials. Trees also removed to clear the area for mining activities, the gazing of animals, the planting of crops and the construction of infrastructure.
Between 2000 and 2010, 52 000 square km of forest was lost every year, which is equivalent to the loss of 142.5 square km of forest per day. The greatest loss of forest occurs in South America, followed by Southeast Asia. Australia and Africa also suffered great losses in forest.
Forests absorb billions of tonnes of CO2 every year via photosynthesis, thus taking in a significant amount of global greenhouse gas emissions. With deforestation, there are fewer trees and other plants to absorb CO2, leading to an increase in CO2 levels in the atmosphere. Soil is one of the largest sources of carbon in the world. Carbon in the soil accumulates through the decay of organic matter such as dead leaves and animals. Deforestation exposes soil to sunlight, increasing soil temperature and the rate of carbon oxidation in the soil. Carbon oxidation is a process by which carbon in the soil reacts with oxygen in the atmosphere to produce CO2. As such, deforestation increases the rate at which carbon dioxide is released from the soil into the atmosphere.

Question 26

Agriculture

Answer 26

Agriculture refers to the practice of cultivating land, producing crops and raising livestock. Rice cultivation and cattle farming can release a large amount of CO2 into the atmosphere. The burning of fossil fuels to power the tractors can release CO2. The use of inorganic fertilisers increases the amount of nitrous oxide in the soil. This substance is released from the soil when soil is ploughed or washed away by rainwater. The deposition of organic matter such as dead leaves and manure releases methane into the air. The rate of decomposition in rice fields is high due to a large amount of moisture in the soil. Cattle farming can release large amounts of methane into the air each year as cattle produce methane as a waste gas due to their slow digestive system. Humans release 0.12kg of methane a year, while a cattle releases 120kg of methane a year. Rice cultivation is commonly found in Southeast Asia countries. Methane from cows account for more than 30% of Argentina’s total greenhouse gas emissions. The increased methane in the atmosphere results in more heat being trapped, increasing global temperatures.

Question 27

Industries

Answer 27

Industries are the production of goods and provision of services within a country. Secondary industries are industrial economic activities that depend on the burning of fossil fuels to provide energy for the manufacture of products as part of their daily operations. Both the burning of fossil fuels and the by-products when goods are produced can release significant amounts of greenhouse gases. The largest carbon dioxide emissions from industries come from North and Central America, Europe and Asia. China and India have also contributed to global greenhouse gas emission significantly due to their rapid industrialisation in the recent years. The manufacture of a mobile phone can emit up to 60kg of CO2. As more manufacturing activities take place, more fossil fuels are burnt, releasing more greenhouse gases into the atmosphere. This will result in more heat being trapped, increasing temperatures.

Question 28

Urbanisation

Answer 28

Urbanisation is the process by which an increasing number of people live in urban areas such as cities or towns. When more people live in urban areas, more energy is required to meet the demand for various household activities and hence, leads to increasing burning of fossil fuels. An urban area also has a large number of cars, buses and other forms of transportation that rely on the burning of fossil fuels to power the engines. Constructing infrastructure and producing construction materials can also emit significant amounts of greenhouse gases into the atmosphere. Singapore is 100% urbanised, which means that all of Singapore’s population lives in an urban area. Their daily activities and use of transport in the urban areas will consume energy and electricity, which will require the burning of fossil fuels. As fossil fuels get burnt, more greenhouse gases are released, trapping more heat, increasing temperatures.

Question 29

Rising sea level

Answer 29

Sea level rise is the increase in the mean height of the sea’s surface between high tide and low tide relative to land. Higher temperatures can cause the glaciers to melt and the water in seas and oceans to expand. Both events can lead to the rise in sea level. The rise in sea level poses a serious threat to human settlements in low-lying areas and islands. There are over 600 million people worldwide who live in areas less than 10 metres above sea level. When the sea level rises, it also threatens about two-thirds of the world’s largest cities that are built along the coastal areas. The Intergovernmental Panel on Climate Change predicts that there will be a loss of 33% of coastal land and wetland habitats in the next hundred years if sea levels continue to increase. As a low-lying island, the rise in sea level poses the most immediate threat to Singapore. Much of our nation lies only 15 m above the mean sea level, with about 30 per cent of our island being less than 5 m above the mean sea level.

Question 30

More frequent extreme weather events

Answer 30

An extreme weather event is a severe and rare weather phenomenon that results in significant economic losses and the loss of human lives. Some extreme weather events include heat waves, floods, droughts and tropical cyclones. The heat wave is an extreme weather event which can kill many people. Extreme weather events have occurred more frequently in the last few decades due to the higher land and sea surface temperatures. Higher land and sea surface temperatures can result in greater amounts of water vapour and latent heat in the atmosphere. This atmospheric change can cause frequent occurrence of extreme weather events and results in heavy losses of properties and human lives. A heat wave killed more than 70 000 people in Europe in 2003. Extreme weather events have been increasing between 1980 and 2005.

Question 31

Spread of some infectious insect-borne diseases

Answer 31

Infectious insect-borne diseases are diseases transmitted to humans and animals by insects. Climate change could increase temperatures and rainfall in certain areas in the world. These favourable conditions encourage insects such as mosquitoes to breed and results in the spread of some infectious insect-borne diseases. The distribution of the occurrence of infectious insect-borne diseases has also changed in the world. Places with moderate temperatures such as Europe and North America have experienced an increasing threat of the same diseases which occurred only in the tropics in the past. Heave rainfall provides more aquatic habitats for mosquitoes to breed. This gives rise to the spread of malaria and dengue fever. Dengue fever cases have been reported in the cool climate areas of Nepal and Bhutan since 2004.

Question 32

Lengthening the growing season in certain regions

Answer 32

The growing season is the period during which crops can be grown. The lengthening growing season in certain places can be caused by higher temperature. This phenomenon has some advantages as well as disadvantages. Growing more variety of crops such as blackberries and maize becomes possible in the UK. Famers enjoy higher harvest of fruits, soybeans, potatoes and wheat in Canada. However, farmers in the Yunnan Province, China, suffered a reduction in the production of fruits such as apples and cherries and nuts such as almonds and walnuts due to shorter cool weather conditions. Farmers in Canada suffer a reduction in wheat grain yield too. The increased global temperatures lead to more optimal temperature for growing of crops. The crops will then have a longer season to grow, increasing food supply. However, crops that require colder climates to grow will see a decrease in production.

Question 33

Kyoto Protocol

Answer 33

The Kyoto Protocol is an agreement linked to the United Nations Framework Convention on Climate Change, which is an international convection set up with the goal of reducing levels of greenhouse gas in the atmosphere. Under the protocol, various targets were set for participating countries to reduce greenhouse gases emissions in the atmosphere, which has been a result of more than 150 years of industrial activity. In this agreement, 37 developed countries and the European countries had greater responsibility to reduce the amount of emissions. Many countries such as Finland, Greece and Ireland had met or exceeded their targets. In addition, the protocol was also successful in encouraging sustainable development as the Clean Development Mechanism gave Certified Emission Reduction credits to countries which carried out emission-reduction projects. However, some countries such as Denmark, Sweden and the UK still fail to meet the emission targets set by the protocol. Under this protocol, countries with low greenhouse gas emissions are not forced to help and support other countries with high greenhouse gas emissions in order to meet their targets easily. This protocol has limited impact on global greenhouse gas emissions because some countries refuse to participate so these countries continue to release large amounts of greenhouse gases. Since 1997, global greenhouse gas emissions had increased 35%, contributed mainly by China, India and the USA.

Question 34

Singapore Green Plan 2012

Answer 34

Singapore Green Plan 2012 was launched by the Ministry of the Environment in 2002. It aims to generate 60% of the country’s energy needs using natural gas by 201 as natural gas is a cleaner form of energy than coal because it does not produce smoke when burnt. As early as 2010, about 79% of the country’s energy needs have been generated by natural gas, which was ahead of the schedule set by the Ministry of Environment. However, natural gas requires complex treatment plants to process and pipelines to transport it. As a result, the maintenance cost is high. The pipelines are laid underground and require regular checks for leakage.

Question 35

Green Mark Scheme

Answer 35

The Green Mark Scheme was launched by the Building Construction Authority in 2005. This scheme allows buildings to be evaluated and certified based on their energy-efficient and environmentally-friendly criteria. It aims to encourage more new ‘green’ buildings which are more energy-efficient. This means that the buildings use less energy to provide the same services, for example, buildings that also make use of solar energy in their functions. There are about 15% to 35% energy savings in existing ‘green’ buildings such as Plaza by the Park, Standard Chartered@Changi and National Library Building as compared to convectional buildings. This reduces the need of burning more fossil fuels to generate electricity and hence, reduces greenhouse gas emissions. However, constructive companies and developers are more conservative about adopting new ideas and materials to build ‘green’ buildings as constructing these ‘green’ buildings involves environmentally-friendly and resource-efficient processes. ‘Green’ buildings incur high construction cost as the materials for constructing ‘green’ buildings can be expensive.

Question 36

Plant-A-Tree programme

Answer 36

It was first started as Tree Planting Day in 1971 before it became the Plant-A-Tree programme with the help of the Garden City Fund and Singapore Environment Council. This programme aims to maintain Singapore’s status as a Garden City by planting trees. Residents can donate money to buy a tree or take part in monthly tree planting events throughout the country. Trees are considered the green lungs of the environment as they help remove CO2 from the atmosphere. This programme has resulted in about 60 000 trees planted yearly in Singapore by the National Parks Board. However, trees require many years to mature. Some relatively fast-growing trees, for example, the angsana, rain tree and yellow flame, take about 25 years to grow to their full height. Therefore, the positive impact of planting trees may not be felt immediately.

Question 37

Tropical Cyclones

Answer 37

Tropical cyclones are weather systems that develop over the warm oceans in the tropics and can range from 150 km to 1500 km. It is found between 8* and 15* north and south of the Equator but not close to the Equator. Heat from the high ocean surface temperatures more than 26.5*C and moisture from the ocean waters enable the tropical cyclone to form.

Question 38

Characteristics of tropical cyclones

Answer 38

Strong winds :
Tropical cyclones have sustained wind speeds of 119 km/hr or more because there is a strong pressure gradient. The atmospheric pressure just above the warm oceanic surface in the centre of the cyclone is very low. The steep pressure gradient results in strong winds spiralling inwards and upwards at high speeds. The spiralling winds at the centre of the cyclone results in a column of sinking air known as the eye.
Low Central Pressure :
Warm and moist air over the warm ocean at the centre of the cyclone expands and rises. As warm air rises, condensation occurs and releases latent heat. Latent heat is the heat energy released when water vapour condenses into water droplets. The continuous large-scale release of latent heat warms the air, causing the air to expand and rise further. This reduces the air pressure near the ocean surface, creating and sustaining an area of low pressure in the centre of the cyclone. As warm air rises, it cools and sinks. The descending dry air create an environment at the centre of they cyclone characterised by calmness and the absence of clouds. This part of the cyclone is known as the eye.

Question 39

Physical impact of tropical cyclones

Answer 39

Tropical cyclones can destroy infrastructure such as roads, bridges and buildings and disrupt communication networks. Damaged roads and bridges hinder the relief effort to deliver emergency supplies such as food, medicines and water to the affected areas. In 2009, Typhoon Ketsuna destroyed road networks in the Philippines, Laos and Cambodia and made the relief effort become difficult. The tropical cyclone destroyed about 80% of the health centres in Manila and hindered the distribution of food and medicine.

Question 40

Economic Impacts

Answer 40

It is costly to repair or rebuild damaged infrastructure and property after the event of tropical cyclones. In 2005, after hurricane Katrina hit the east coast of the USA, the cost of repairs of damaged property was estimated to be about US$81 billion. The cost of repair to infrastructure as they are destroyed by the storm surges and strong winds leads to less money to build other aspects of the economy.

Question 41

Social Impacts

Answer 41

Tropical cyclones can damage water pipes or pumps and disrupt fresh water supply. People living in the affected areas will not have access to fresh water anymore. They can also damage sewage pipes and cause sewage to leak out from the burst pipes and contaminate clean water supplies. This situation can cause the spread of water-borned diseases such as cholera and typhoid fever when people consume contaminated water. When Cyclone Aila hit West Bengal India in 2009, it caused the contamination of drinking water and led to a cholera outbreak, infecting 1000 people and killing 14 people.

Question 42

Emergency action

Answer 42

Emergency action refers to taking immediate action to respond to a situation that poses risk to people’s lives and health. Government may issue weather warnings and advisories so that the people have enough time to make preparations to protect their lives and properties. This will help minimise injury and death when a tropical cyclone strikes. A cyclone-proof place, for example a community cyclone shelter, may be built close to the homes of the people in areas prone to tropical cyclones. This place is built with strong concrete which are raised above the ground to withstand the hazards linking with tropical cyclones. People can be evacuated to the shelter easily before the cyclone strikes. Countries such as Bangladesh and India experience a reduced number of casualties with the use of community cyclone shelters. However, emergency action requires assistance from the national government as well as governments of neighbouring countries to help repair the damaged infrastructure and to provide aid to the victims. This measure also requires the help from non-governmental organisations such as Red Cross, Oxfam and Save the Children to provide relief teams and aid in terms of clothing, food and health care, to the victims living in the affected areas.

Question 43

Prediction and Warning

Answer 43

Through analysing long term climate records, cyclones can be predicted as a pattern of occurrence and the severity of damage caused by past cyclones can be observed. This gives authorities an indication about the severity of impacts caused by cyclones, hence allowing them to prepare the population for natural disasters of a similar magnitude. In addition, computer modelling also allows for prediction to be made about the cyclone’s path, the likely affected areas as well as the extent of the damage. Although these predictions are not completely accurate, they serve as a warning to the population so that they can evacuate quickly, lessening the damage of the cyclones. For example, Japan and the USA are some countries that have installed warning systems for tropical cyclones that can warn the public of the disasters prior to the onset of a cyclone. However, climate records of past events only indicate the frequency and does not give accurate details about when future cyclones will occur.

Question 44

Land use control

Answer 44

With the use of land use controls, the impact of cyclones can be reduced as the density of population at an area is reduced. Two types of land use controls include coastal plain management and flood plain management. Authorities impose higher taxes on developers to deter them from using the land at these vulnerable areas. These lands can instead be used for recreational areas such as parks to lower the population density at high-risk areas. In addition, the government might also adopt the use of flood plain management to reduce the potential of floods in an area. By mapping out the area prone to flooding, authorities can ensure that new developments are not located in these areas. Evacuation plans can also be drawn up to ensure that people can evacuate quickly in times of floods. For example, in Cairns, Australia, the authorities rely on flood plain management plans to plan out evacuation routes so that during flooding, the citizens can evacuate effectively and quickly, thus reducing the damage of the tropical cyclones. Although these methods to reduce the impacts of cyclones are largely effective, some residents may be reluctant to move out of these areas as they have been staying there for a long time. The authorities will also need to be able to enforce the rules and map out the flood prone areas which requires time and manpower.

Question 45

Reducing vulnerability of infrastructures

Answer 45

To further reduce the damage from hazards associated with a tropical cyclone, authorities need to reduce the vulnerability of infrastructure. Roof of buildings can be refitted with galvanised steel hurricane ties to prevent it from being blown off by the strong winds of tropical cyclones. In addition, to protect against storm surges, protective barriers such as river embankments and coastal dikes can be constructed and inspected and reinforced regularly as these barriers sustain damages due to continued erosion. For example, the construction of a protective barrier along the coast in Apia, Samoa, protected the coastline and the harbour when cyclone Val struck the island in 1991. Lastly utility lines such as power and telecommunication lines and water supply networks can also be placed underground to avoid damage by strong winds and storm surges. This will thus ensure that services are maintained during and after a tropical cyclone. However, it is costly so not all countries can afford.