2. QUESTIONS
1. What is the difference between weather and
climate?
2. What are the elements of weather?
3. BY THE END OF THE LESSON
We will be able to
1. Differentiate between weather and climate.
2. List the elements of weather.
3. Measure temperature.
4. Describe temperature of place.
4. WEATHER AND CLIMATE
• Weather is the condition of the atmosphere at
a particular place and time.
• Climate is the average condition of the
atmosphere of a specific place over a long
period of time, usually over 30 years.
5. ELEMENTS OF WEATHER
1. Temperature
– Latitude
– Altitude
– Distance from the sea
– Cloud cover
2. Relative humidity
3. Cloud cover
4. Rainfall
5. Air pressure
6. Wind
6. TEMPERATURE
• The degree of hotness or coldness of a place.
– > 20°C = High temperatures
– < 10°C = Low temperatures
7.
8. MAXIMUM-MINIMUM
THERMOMETERS
• Used to measure the maximum and
minimum temperatures of a day.
• Metal index in the maximum thermometer
will stay at the maximum temperature
recorded.
• Metal index in the minimum thermometer
will stay at the minimum temperature
recorded.
10. TEMPERATURE CALCULATIONS
Temperature
calculation
Definition Formula
Mean daily
temperature
Sum of hourly temperatures
divided by 24 hours
Sum of hourly temperatures
24
Diurnal
temperature
Range
Difference between the max.
and min. temperatures
recorded in a day
Max. daily temperature –
min. daily temperature
Mean monthly
temperature
Average daily temperatures
recorded in a month
Sum of mean daily
temperatures in the
month/Number of days in
the month
Mean annual
temperature
Average temperature
recorded in a year
Sum of mean monthly
temperatures in the year/12
Annual
temperature
range
Difference between the max.
and min. mean monthly
temperatures recorded in a
year
Max. mean monthly
temperatures – min. mean
month temperature
17. LATITUDE
• Along the Equator, the Sun’s rays strike the
Earth’s surface perpendicularly.
• The high angle of incidence causes the solar
radiation to be concentrated over a smaller
area, causing more intense heat hence the
equatorial region experiences a higher
temperature.
18. LATITUDE
• At the higher latitudes, the Sun’s rays strike
the Earth’s surface at smaller angles of
incidence.
• This causes the solar radiation to be spread
over a larger area, hence the higher latitudes
experiences a lower temperature.
20. LATITUDE
• About 50% of the solar energy that reaches
the atmosphere's upper layers are absorbed
by oxygen, ozone and other molecules before
it reaches the surface.
• More solar energy would have been lost at the
higher latitudes as the Sun’s rays need to
travel over a greater distance through the
atmosphere before reaching the Earth’s
surface.
22. ALTITUDE
• Altitude refers to the height of a point in
relation to the sea level.
• Temperatures generally decrease by 6.5°C
with every 1000m increase in altitude.
23. ALTITUDE
• About 45 percent of the sun’s energy is
directly absorbed by the Earth’s surface,
which in turn emits more heat.
• Temperature decreases as altitude increases
due to the increased distance from the earth’s
surface.
24. ALTITUDE
• The atmosphere consists of water vapour and
other gases which absorb heat from the Sun.
• Due to the force of gravity, there is a higher
concentration of atmospheric molecules at or
near sea level hence most of the Sun’s heat is
absorbed at that level.
• In addition, the same atmospheric molecules
are warmed by heat radiated from the Earth’s
surface hence temperature is higher at the
lower altitudes.
25. QUESTIONS
1. During the day, is temperature higher or
lower when there are more/less clouds?
2. Why?
27. CLOUD COVER
• Temperatures are higher on days where
clouds are absent,
• as the absence of clouds allows large amounts
of the sun’s energy to reach the Earth,
• thereby heating up the Earth’s surface which
in turn heats up the air near the Earth’s
surface.
28. CLOUD COVER
• Temperatures are lower on cloudy days,
• as clouds reflect a large portion of the sun’s
energy (solar radiation) back to space.
• Clouds also absorb heat radiated from the
Earth’s surface.
30. CLOUD COVER
• Temperatures are higher on cloudy nights,
• as clouds absorb more of the heat that is
radiated from the Earth’s surface and prevent
it from escaping into space.
31. CLOUD COVER
• Temperatures are lower on nights where
clouds are absent,
• as the absence of clouds allows more of the
heat radiated from the earth’s surface to
escape into space.
32. QUESTIONS
• Why are summers cooler and winters warmer
at coastal areas than inland areas?
• Hint:
– Consider the properties of seas (liquid) and
land areas (solid)?
33. DISTANCE FROM THE SEA
• Seas and oceans takes a longer time to heat
up, but once heated up will retain heat longer.
• Land, on the other hand, heats up very
quickly and loses heat quickly.
34.
35. DISTANCE FROM THE SEA
• Maritime effect:
– During summer, the air over the sea is cooler than
the air over the land as land heats up quickly while
the sea heats up slowly.
– The cooler air over the sea helps lower the
temperature of coastal areas, leading to cool
summers.
– During winter, the air over the sea remains
warmer than the air over the land as the sea cools
more slowly than the land, leading to warmer
winters.
36. DISTANCE FROM THE SEA
• Continental effect:
– During summer, the air over the land heats
up quickly leading to warmer summers.
– During winter the air over the land loses heat
quickly leading to colder winters..
38. BY THE END OF THE LESSON
We will be able to
1. Explain how relative humidity affects
weather and climate.
39. QUESTIONS
1. Why do we feel sticky or clammy during hot
days?
• Answer: Too much water vapour in the air
slows down the evaporation of our
perspiration.
2. How do water vapour enter the air then?
3. What affects the humidity of the air?
40. RELATIVE HUMIDITY
• Relative humidity is the proportion of the actual
amount of water vapour in a mass of air
• compared to the maximum amount of water vapour
the air can hold at a given temperature.
• Formula:
• Actual amount of water vapour in the air (g/m3) x
100% /
• Maximum amount of water vapour the air can hold
(g/m3)
42. RELATIVE HUMIDITY
1. The amount of water vapour in the air
– When the amount of water vapour in the air
increases without any change in temperature,
relative humidity increases.
– When the amount of water vapour in the air
decreases without any change in temperature,
relative humidity decreases.
43. RELATIVE HUMIDITY
2. Temperature
– Warm air can hold more water vapour than
cool air.
– When temperature increases without any
change to the amount of water vapour in the
air, the rise in temperature makes air more
able to hold water vapour, hence relative
humidity decreases as temperature increases.
44. RELATIVE HUMIDITY
• Saturation of the air occurs when relative
humidity is 100%.
• The temperature at which saturation occurs is
known as the dew point temperature.
45. RELATIVE HUMIDITY
• Sling psychrometer
– Instrument used to measure relative humidity
– Consists of two thermometers
• Dry thermometer
• Wet thermometer
46. RELATIVE HUMIDITY
• Using a sling psychrometer
– Wet the wick of the wet bulb thermometer.
– Swing the psychrometer at about 2 turns per
second for 1 minute.
– After 1 minute, record the wet-bulb temperature.
– Swing the psychrometer for another minute and
record the wet-bulb temperature again.
– If the reading is different from your previous
reading, swing for another minute and check
again.
– Repeat as necessary until the same temperature is
recorded consecutively.
47. RELATIVE HUMIDITY
– Record the dry-bulb temperature against the
lowest wet-bulb temperature.
– Find the difference between the wet-bulb and the
dry-bulb temperature to derive the wet bulb
depression.
– Derive the relative humidity using the relative
humidity table.
– Relative humidity is the intersect between the
dry-bulb temperature and the difference between
the wet-bulb and dry-bulb temperature.
49. RELATIVE HUMIDITY
• How does the sling psychrometer work?
– Whirling the wet-bulb thermometer causes
the water on the wet cotton to evaporate.
– The evaporation cools the bulb of the wet-
bulb thermometer.
– The drier the ambient (surrounding) air, the
more evaporation and associated cooling can
take place, the lower the reading of the wet-
bulb thermometer.
50. RELATIVE HUMIDITY
• To ensure accurate readings
– Avoid holding the sling psychrometer too close to
the body to prevent the thermometers from
picking up body heat.
– Avoid holding the sling psychrometer too close to
the ground.
– Avoid touching the bulbs of the thermometers.
– Read the wet-bulb temperature fast.
– Take more than one reading from the wet-bulb
thermometer to ensure the lowest possible
reading.
59. CLOUDS
• Water is converted to water vapour through
evaporation.
• As water vapour rises, it starts to cool.
• When the water vapour cools to dew point
temperature, and there are particles for the water
vapour to condense on, condensation takes place
to form water droplets.
• As these water droplets bump against each other
and become larger in a process called
coalescence, clouds form.
60. PRECIPITATION
• Refers to water in any form that falls from the
atmosphere to the surface of the earth.
• Includes hail, snow, sleet, and rain.
• High rainfall: > 1500mm
• Moderate rainfall: 251mm – 1499mm
• Low rainfall: < 250mm
61. QUESTIONS
1. Why are cumulonimbus clouds a common
sight during warm afternoons in tropical
countries?
2. Why do tropical countries such as Singapore
experience frequent afternoon showers?
62. CONVECTIONAL RAIN
• As the sun’s energy heats up the earth’s surface,
the warm surface heats the air around it.
• The air becomes unstable, causing it to expand
and rise.
• As the air rises, its temperature begins to drop.
• When the rising air cools to dew point
temperature, condensation occurs and clouds are
formed.
• When the water droplets in the clouds become
large and heavy enough, they fall to the ground
as convectional rain.
63.
64. RELIEF / OROGRAPHIC RAIN
• Air picks up moisture as it passes over the sea and
arrives at the coast.
• As moist air is forced to rise up the windward side
of the mountain, it cools.
• When the temperature of the air reaches dew
point, condensation occurs and clouds form.
• When the water droplets become large and heavy
enough, they fall as relief rain.
• This explains why the leeward side of a mountain
is usually dry as most of the moisture would have
fallen on the windward side.
69. AIR PRESSURE
• Refers to the force exerted on an unit area of
the earth’s surface by the weight of a column
of air above it.
• Air pressure is measured in millibars (mb).
• Average air pressure at sea level is 1013 mb.
• High air pressure > 1013 mb
• Low air pressure < 1013 mb
70. QUESTIONS
1. What is the relationship between
temperature and air pressure?
2. What is the relationship between altitude
and air pressure?
71.
72. 0
5
10
15
20
25
30
35
0 200 400 600 800 1000 1200
Altitude(km)
Air Pressure (mb)
Relationship between altitude and air pressure
74. WIND
• Air moves from an area of high pressure to an
area of low pressure.
• This movement of air is known as wind.
• Wind is described in terms of speed,
direction and frequency.
75. WIND
• Wind speed:
– Rate at which air is moving
• Wind direction
– Direction from which wind is blowing from
• Wind frequency
– Percentage of time wind blows from a
particular direction
– Winds that blow most frequently from a
specific direction are called prevailing wind.
77. LAND BREEZE
• During the night, the land cools down faster than the
sea.
• As cool air over the land sinks, a high pressure area is
formed.
• Air over the sea is warmer as the sea loses heat slower.
• The warm air over the sea rises and forms a low
pressure area.
• As air moves from a high pressure area to a low
pressure area, this causes air to move from the land
towards the sea, forming a land breeze.
79. SEA BREEZE
• During the day, the land heats up faster than the sea.
• As the warm air over the land rises, a low pressure
area is formed.
• Air over the sea is cooler as the sea heats up slower.
• The cool air over the sea sinks and forms a high
pressure area.
• As air moves from a high pressure area to a low
pressure area, this causes air to move from the sea
towards the land, forming a sea breeze.
82. BY THE END OF THE LESSON
We will be able to
1. Describe the effect of the Coriolis Effect on
winds.
2. Explain the formation of monsoon winds.
83. CORIOLIS EFFECT
• Refers to the force produced by the Earth’s
rotation.
• As the Earth rotates, the Coriolis Effect changes
the course of moving objects that are fluid,
causing them to curve they travel across or above
the Earth’s surface.
• In the northern hemisphere, the Coriolis Effect
deflects winds to the right,
• while in the southern hemisphere, winds are
deflected to the left.
86. BY THE END OF THE LESSON
We will be able to
1. Describe and explain the formation of
monsoon winds.
87. MONSOON WINDS
• Refers to regional wind patterns that reverse
direction seasonally, leading to seasonal
changes in precipitation.
88. NORTHEAST MONSOON
• Between October and February, the southern
hemisphere experiences summer.
• Air over Australia heats up and rises, forming
a region of low pressure.
• During the same period, the northern
hemisphere experiences winter.
• Air over continental Asia cools and sinks,
forming a region of high pressure.
89.
90. NORTHEAST MONSOON
• Due to the difference in pressure, air moves
from continental Asia towards Australia
• As the winds travels towards India, they
deflect to the right to become the Northeast
monsoon.
• The Northeast monsoon that travels towards
India and Bangladesh are cool dry winds as
little moisture is picked up from continental
Asia.
91.
92. NORTHEAST MONSOON
• In contrast, the winds that travel towards the
Equator are heavily laden with moisture as they
absorbed water vapour from the South China
Sea.
• Thus, when they reach Peninsular Malaysia and
Singapore, they bring large amounts of rain.
• After crossing the Equator into the southern
hemisphere, the winds are deflected to the left
and picks up moisture as it travels over the
Indian Ocean towards Australia, bringing rain to
Indonesia and Australia.
93.
94. SOUTHWEST MONSOON
• Between June and September, the northern
hemisphere experiences summer.
• Air over continental Asia heats up and rises,
forming a region of low pressure.
• During the same period, the southern
hemisphere experiences winter.
• Air over Australia cools and sinks, forming a
region of high pressure.
95.
96. SOUTHWEST MONSOON
• Due to the difference in pressure, air moves
from Australia towards continental Asia as
the southeast monsoon winds.
• After crossing the Equator into the northern
hemisphere, the winds are deflected to the
right to become the southwest monsoon
winds.
97.
98. SOUTHWEST MONSOON
• The Southwest monsoons bring much rain to
the southwestern parts of India and Sumatra
as they picked up moisture across the ocean.
• However, Peninsular Malaysia and Singapore
receive much less rain during the Southwest
monsoon season because the high mountain
ranges in Sumatra forced the winds to deposit
their moisture as relief rain.
101. BY THE END OF THE LESSON
We will be able to
1. Describe the characteristics of the equatorial
climate, monsoon climate and cool
temperate (marine west coast) climate.
105. EQUATORIAL CLIMATE
• Between 10°N and 10°S of the Equator.
• E.g. Singapore, Malaysia, Colombia
• High mean annual temperatures of 27°C
• Small annual temperature range of 2°C – 3°C
• High relative humidity
• Frequent convectional rain
• Total annual rainfall > 2000mm
• No distinct wet and dry seasons
108. MONSOON CLIMATE
• Between 5°N and 25°N and 5°S and 25°S of the
Equator.
• E.g. Chittagong, Bangladesh and Mumbai,
India
• High mean annual temperatures of 26°C
• Small annual temperature range of 6°C
• Distinct wet and dry seasons
• > 2000mm during wet seasons, about 750mm
during dry seasons
111. COOL TEMPERATE
(MARINE WEST COAST)
• Between 45°N and 60°N of the Equator
• E.g. Paris, France and Toronto, Canada
• Low mean annual temperatures
• High annual temperature range of around
25°C
• 4 distinct seasons
• Mild winters, cool summers
• Generally evenly distributed rainfall
• Total annual rainfall 300mm – 900mm
113. BY THE END OF THE LESSON
We will be able to
1. Describe how global climate has changed.
2. Account for the natural causes of climate
change.
114. GLOBAL CLIMATE CHANGE
• Refers to the variation in the global climate or
climatic patterns in the long term.
115. GLOBAL CLIMATE CHANGE
• Since the 1800s, the Earth has experienced
irregular temperature increases of between
0.3°C and 0.6°C.
• The rate of increase is faster between 1980
and 2000, increasing by about 0.4°C over
those 2o years alone.
• Over the last century, the Earth has warmed
by an average 0.74°C.
116. GLOBAL WARMING AND COOLING
• Global warming and cooling refers to the
increase and decrease in global temperatures
respectively over a long period time.
120. VARIATIONS IN SOLAR OUTPUT
• The Sun emits varying amounts of solar
radiation due to changes in its magnetic
activity over an 11 year cycle.
• An increase and decrease in magnetic activity
will result in an increase and decrease in solar
radiation respectively,
• and contribute to the Earth’s cycle of high
and low global temperatures.
121. VOLCANIC ERUPTIONS
• Volcanic eruptions release large amounts of
carbon dioxide, dust and ash into the
atmosphere.
• These particles reflect solar energy back into
space and leads to global dimming, or the
reduction in the amount of sunlight reaching
the Earth's surface,
• thereby cooling the Earth temporary for
months or a few years.
123. BY THE END OF THE LESSON
We will be able to
1. Describe the greenhouse effect.
2. Describe the enhanced greenhouse effect.
3. Describe how human activities lead to
enhanced greenhouse effect.
124. GREENHOUSE EFFECT
• Shortwave radiation
– Electromagnetic radiation with shorter
wavelengths
– More easily absorbed by hard surfaces
• Longwave radiation
– Electromagnetic radiation with longer
wavelengths
– Easily absorbed by greenhouse gases such as water
vapour, carbon dioxide, methane, nitrous oxide
and ozone.
126. GREENHOUSE EFFECT
1. Incoming shortwave radiation from the sun enters
the atmosphere.
2. Some shortwave radiation is reflected by the Earth
back into space.
3. Most of the shortwave radiation is absorbed by the
Earth.
4. Longwave radiation is emitted by the warmed
surface of the Earth.
5. The greenhouse gases in the atmosphere absorb and
reflect the longwave radiation back to Earth,
thereby warming the atmosphere in a process
known as the greenhouse effect.
127. ENHANCED GREENHOUSE EFFECT
• Refers to the rise in global temperatures as a
result of an increase in the concentration of
greenhouse gases in the atmosphere, brought
about by human activity.
129. ENHANCED GREENHOUSE EFFECT
• Overall increase in carbon dioxide, methane and
nitrous oxide.
• The amount of carbon dioxide remained stable at
275ppm until the 1850s.
• The amount of methane remained stable at
around 800 ppb until the 1850s.
• The amount of nitrous oxide remained stable at
around 260ppm until the 1850s.
• After the 1850s, all three gases experienced a
sudden increase, with carbon dioxide and nitrous
oxide increasing the most.
131. HUMAN ACTIVITIES AND THE
ENHANCED GREENHOUSE EFFECT
1. Burning fossil fuels
2. Deforestation
3. Agriculture
4. Industries
5. Urbanisation
132. BURNING FOSSIL FUELS
• Fossil fuels such as coal and oil are formed
from dead organic matter that has
decomposed over many millions of years.
• Due to their high carbon content, fossil fuels
contribute to the increase in greenhouse
gases by producing large amounts of carbon
dioxide when burnt.
133. DEFORESTATION
• Forests absorb billions of tonnes of carbon
dioxide every year and deforestation leads to
fewer vegetation to absorb carbon dioxide,
resulting in an increase in carbon dioxide
levels in the atmosphere.
134. AGRICULTURE
• Cattle farming contributes to greenhouse gas
emissions as millions of tonnes of methane is
released by cattle each year due to their slow
digestive system.
135. INDUSTRIES
• Industries such as manufacturing contribute
to greenhouse gases carbon dioxide as they
involve the burning of fossil fuels in their
daily operations.
136. URBANIZATION
• Urbanization results in the increase in the use
of fossil fuels to provide energy for household
activities such as heating, cooking lighting
and transportation.
137. BY THE END OF THE LESSON
We will be able to
1. Describe the impact of the enhanced
greenhouse effect on people.
139. IMPACT OF CLIMATE CHANGE
1. Sea level rise
2. More frequent extreme weather events
3. Spread of some infectious insect-borne
diseases
4. Length of growing season in certain regions
140. SEA LEVEL RISE
• Refers to the increase in the mean height of the
sea’s surface between the high and low tide
relative to land.
• Higher temperatures are causing the melting of
glaciers and expanding the water in the seas and
oceans, which led to the rise in sea level.
• The rise in sea level is a serious threat to human
settlements that are located at or around sea level
as properties and infrastructure would be lost if
sea levels continue to rise.
141. EXTREME WEATHER EVENTS
• Refers to a severe weather phenomenon that
results in significant economic losses and the
loss of lives.
• The increase in global temperatures have
resulted in greater amounts of water vapour
and latent heat in the atmosphere.
• These atmospheric changes have led to the
occurrence of more extreme weather events
such as hurricanes and heat waves, resulting
in heavy loss of properties and lives.
142. INFECTIOUS INSECT-BORNE DISEASES
• Refer to diseases that are transmitted to humans
and animals by insects.
• Heavy rainfall brought about by climate change
has created more habitats for mosquitoes, which
are carriers of diseases such as malaria and
dengue.
• This has led to an increase in the distribution of
the occurrence of insect-borne diseases to
include regions that were previously inhabitable
for mosquitoes, such as those with moderate
temperatures.
143. LENGTH OF GROWING SEASON
• Growing season refers to the period during which
crops can be grown.
• The increase in greenhouse gases has led to
rising temperatures which affected the growing
season of crops.
• For example, it is now possible to grow
blackberries and maize in the United Kingdom.
However, it has led to shortened growing season
in Yunnan, China and Canada.
• This has the effect of reducing income and jobs
which may lead to economical problems.
147. TASK
• Evaluate the effectiveness of international
responses in reducing the impact of climate
change. [8]
148. KYOTO PROTOCOL
• Point:
– The Kyoto Protocol is an international agreement
set up with the goal of reducing the levels of
greenhouse gases in the atmosphere.
• Explain:
– It is effective in reducing the impact of climate
change as many signee countries have met or
exceeded the targets set by the Kyoto Protocol and
funds were made available to less developed
countries to help them reduce greenhouse gas
emissions.
149. KYOTO PROTOCOL
• Example:
– For example, signee countries such as Austria, Finland
and Greece met or exceeded their targets and less
developed countries such as Angola and Cambodia
were able to reduce their emissions with the help of
resources from the more developed countries.
• Limitation:
– However, the Kyoto Protocol is limited in its
effectiveness as signee countries such as Denmark and
the United Kingdom did not achieve their targets. In
addition, countries who are not signees continue to
contribute to global emissions.
150. COPENHAGEN CONFERENCE
• Point:
– The Copenhagen Conference was organized to
improve on the measures developed for the Kyoto
Protocol to deal with the issue of climate change.
• Explain:
– It is effective in reducing the impact of climate
change as the conference as solid agreements were
forged during the conference to reduce
greenhouse gas emissions.
151. COPENHAGEN CONFERENCE
• Example:
– For example, the Copenhagen Accord was drawn
up during the conference with the long-term goal
of managing the global mean maximum
temperature. In addition, more funds were
pledged to help less developed countries.
• Limitation:
– However, there was no agreement on how to
reduce the greenhouse gas emissions and the
targets are not legally binding, hence many
countries did not keep to their targets.
152. BY THE END OF THE LESSON
We will be able to
1. Evaluate the effectiveness of national
responses to climate change.
153. NATIONAL RESPONSES
Singapore
1. Singapore Green
Plan 2012
2. Green Mark
Scheme
3. Plant-A-Tree
Programme
India
1. National Urban
Transport Policy
2. Energy Labelling
Programme
3. The Indian Network
of Climate Change
154. TASK
• Evaluate the effectiveness of national
responses in reducing the impact of climate
change. [8]
156. BY THE END OF THE LESSON
We will be able to
1. Describe the distribution of tropical
cyclones.
2. Describe the characteristics of tropical
cyclones.
157. TROPICAL CYCLONES
• Refer to weather systems that develop over
the warm oceans in the tropics and can range
from 150 kilometres to 1500 kilometres.
159. WHERE ARE TROPICAL CYCLONES FOUND?
• Found between 8° and 15° north and south of
the Equator.
• Areas with warm waters of around 26.5°C and
the presence of the Coriolis Effect.
162. STRONG WINDS
• The atmospheric pressure just above the
oceanic surface in the centre of a cyclone is
much lower than above the cool oceanic
surface outside the centre.
• This creates a steep pressure gradient that
leads to sustained strong winds spiraling
inwards and upwards at high speeds.
163. LOW CENTRAL PRESSURE
• Warm and moist air over the warm oceanic
surface at the centre of the cyclone expands
and rises, leading to condensation which
releases latent heat.
• The continuous release of latent heat warms
the air, causing the air to expand and to rise
further, creating and sustaining an area of
low pressure in the centre of the cyclone.
164. BY THE END OF THE LESSON
We will be able to
1. Describe how tropical cyclones are affected
by the Coriolis Effect.
2. Describe the hazards associated with
tropical cyclones.
3. Describe the impact of tropical cyclones
165.
166. INFLUENCE OF THE CORIOLIS EFFECT
• The strong pressure gradient causes air to move
straight inwards to the cyclone.
• However, due to the Coriolis Effect, the air moves
at an angle instead.
• In the northern hemisphere, the Coriolis Effect
deflects wind to the right, causing tropical
cyclones to rotate in an anti-clockwise direction.
• In the southern hemisphere, the Coriolis Effect
deflects wind to the left, causing tropical
cyclones to rotate in a clockwise direction.
168. STORM SURGE
• Refers to a sudden rise in sea level in which
water is piled up against a coastline beyond
the normal conditions at high tide.
• Storm surges are formed when strong winds
pushes the water at above sea level as the
result of the intense low pressure at the eye,
towards the coast, creating huge waves that
threatens lives and property along the coast.
169. WIND DAMAGE
• Tropical cyclones are accompanied by very
strong winds capable of destroying property
and loosing debris over a large area, causing
even more damage.
170. TORRENTIAL RAIN
• Tropical cyclones produce sudden and large
amounts of rainfall that can cause rivers and
streams to overflow, leading to inland
flooding that threatens lives and property.
171. IMPACT OF TROPICAL CYCLONES
1. Physical impact
2. Economic impact
3. Social impact
176. EMERGENCY ACTION
• Point:
– Emergency action involves taking immediate
action in response to any situation that poses
risk to people’s health and lives.
• Explain:
– This is an effective response as people can be
evacuated to safe destinations such as cyclone
shelters before a tropical cyclone occurs, and
receive aid after.
177. EMERGENCY ACTION
• Example:
– For example, the use of cyclone shelters has greatly
reduced the number of casualties in countries such as
India. Assistance from the Red Cross after Typhoon
Haiyan has provided relief for many families in the
form of food packages and other necessities.
• Limitation:
– However, cyclone shelters are not readily accessible to
all and organizations such as Red Cross are usually
hindered by the shortage in funding.
178. PREDICTION AND WARNING
• Point:
– Predicting tropical cyclones is by analysing
long-term records to establish the pattern and
occurrence of past cyclones.
• Explain:
– This is an effective response as it is possible to
predict when cyclones would occur and apply
preemptive measures such as warnings before
they occur.
179. PREDICTION AND WARNING
• Example:
– For example, Japan and the USA have installed
warning systems for tropical cyclones which were
able to provide people with information before
their occurrence, thereby reducing the number of
causalities and damages.
• Limitation:
– However, due to the quick changing weather
condition, the predictions may not always be
accurate and the warnings may sometimes go
unheeded.
180. LAND USE CONTROL
• Point:
– Land use control refers to the regulation of
land by placing restrictions on how the land
can be used.
• Explain:
– This is an effective response as restricted
zones may restrict or bar development
altogether, thereby reducing the human and
property loss caused by cyclones.
181. LAND USE CONTROL
• Example:
– For example, areas along the coasts that are
vulnerable to storm surges and flooding caused by
tropical cyclones may require developers to pay
higher taxes as deterrence, and protected zones
can serve as a barrier against storm surges.
• Limitation:
– However, land use controls are only successful
when the authorities are able to enforce them and
residents who have been living in areas newly
designated restricted may be reluctant to move.
182. FLOODPLAIN MANAGEMENT
• Point:
– Floodplain management refers to the
management of low-lying areas near rivers or
the coast that are prone to flooding.
• Explain:
– This is an effective response as careful
management ensures that developments in
floodplains are flood-resistant, and that
effective evacuation plans can be designed.
183. FLOODPLAIN MANAGEMENT
• Example:
– For example, developments in the floodplain for
Cairns, Australia are designed to be flood-
resistant and evacuation plans are drawn with
reference to storm surge flood models.
• Limitation:
– However, there was no agreement on how to
reduce the greenhouse gas emissions and the
targets are not legally binding, hence many
countries did not keep to their targets.
184. REDUCING VULNERABILITY
OF INFRASTRUCTURE
• Point:
– Reducing the vulnerability of infrastructure
includes designing buildings that are resistant
to damages caused by cyclones.
• Explain:
– This is an effective response as
infrastructure that are more resistant to the
damaging effects of cyclones will reduce the
loss of human lives and property when
cyclones occur.
185. REDUCING VULNERABILITY
OF INFRASTRUCTURE
• Example:
– For example, in Florida, USA, homeowners are
aided by the state government in improving their
houses against cyclone attacks, which led to only
minor damage to houses when Hurricane Wilma
struck in 2005.
• Limitation:
– However, such improvements require finacial
inputs from house owners and not every house
owner may be able to afford the upgrades, thereby
limiting its effectiveness.
