This document provides information about weather and climate elements such as temperature, humidity, clouds, rainfall, and pressure and winds. It discusses factors that affect temperature like latitude, altitude, distance from the sea, and cloud cover. It also explains concepts such as relative humidity, cloud formation, convectional and relief rainfall, land and sea breezes, and monsoon winds. Students are prompted to think about questions related to these topics and provided exercises to reinforce their understanding.

1. VARIABLE WEATHER & CHANGING
CLIMATE
1. Why do different places experience different weather and climate?
2. What is happening to the Earth’s climate?
Copy when you see:

2. IMPORTANT NOTE
• For unit 2, Weather
–Please bring your text book, we are using
the exercises inside.

3. THINK ABOUT THIS…
GATEWAY 1: Why do different places experience
different weather and climate?
• Why does Singapore not have any snow?
• How does knowing the weather the next day
help you to plan your activities?
• Why does it always feel so warm in the evening
despite the temperature falling?
• Why does it rain so often in Nov/Dec?
• More questions from you?

4. Elements of Weather
• Temperature
• Relative Humidity
• Clouds
• Rainfall
• Pressure and Winds

5. TEMPERATURE
• Measures the degree of hotness or coldness
• Energy of sun -> Travels through atmosphere ->
Absorbed by earth’s surface -> Surface warms
up -> Heats up atmosphere
• Temperature measurement = oC
• Maximum and minimum temperature
• Diurnal temperature range
• Mean daily/monthly/annual temperature
• Annual temperature range

6. Maximum and minimum temperature
• The highest and lowest temperatures
recorded within a day.
• Normally affected most by the
presence or absence of sunlight (key
heatsource)

7. Diurnal Temperature
• The difference between the Maximum and
minimum temperature of the day.
January 1 2 3 4 5 6 7 8 9 10 11 12
Maximum 26 27 27 26 28 28 28 28 29 29 27 25
Minimum 25 25 25 24 25 25 24 25 25 26 26 24

8. Mean annual temperature
• The average of all the monthly average
temperatures
• Sum of all divided by 12 months.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
COUNTRYC -30 -28 -25 -20 -16 -15 -10 -16 -22 -29 -30 -35
COUNTRYD 27 27 28 28 29 30 32 30 30 29 28 28

9. Annual Temperature Range
• The variation of temperature between the
monthly average temperature readings.
• Difference between the highest and lowest
recorded temperatures.

10. Land Breeze
• Coastal effect experienced at night
• Sea retains heat better at night, air parcel
above the sea is warmer.
• Warmer air rises up, leaving a vacuum.
• The cooler air above the land rushes out to
the sea.
• This movement of air from land to sea forms
the land breeze

11. Land Breeze Diagram

12. Sea Breeze
• Coastal effect experienced in the day
• The air above the land heats up faster than
the air above the water.
• Warmer air rises up, leaving a vacuum.
• The cooler air above the sea rushes into the
land.
• This movement of air from sea to land forms
the sea breeze

13. Sea Breeze Diagram

14. TEMPERATURE
• Temperature can be affected by:
– Latitude – textbook page 75
– Altitude – textbook page 76
– Distance from the sea – textbook page
77
– Cloud cover – textbook page 77

15. Latitude

16. Altitude

17. Distance from sea

18. Cloud coverage

19. FACTORS AFFECTING TEMPERATURE
• Maritime Effect
– The effect of large ocean bodies on climate of
coastal areas
– During summer the air over the sea remains cooler
than the land as it heats up slower
– During winter the air over the sea remains warmer
than the land as it loses heat slower
– This causes coastal areas to have cooler summers
and warmer winters
– The annual temperature range is thus smaller

20. FACTORS AFFECTING TEMPERATURE
• Latitude
– Imaginary horizontal lines running east to west
– Equator = 0o
– North / South Pole = 90oN / 90oS
– Angle of incidence: refers to the sun’s rays hitting
the earth surface at an angle
– A higher angle of incidence means more
concentrated sunlight

21. FACTORS AFFECTING TEMPERATURE
• Altitude
– Refers to the height of a location in relation to the
sea level
– Temperature decreases with altitude
– The higher the altitude, the lower the temperature
– Earth’s atmosphere is mostly heated by the surface
– Shortwave radiation: sun’s solar energy reaching
the earth’s surface
– Longwave radiation: Earth’s surface emitting heat
to heat up the atmosphere

22. FACTORS AFFECTING TEMPERATURE
• Altitude
– Density of air becomes lower as altitude becomes
higher
– Dense air absorbs more longwave radiation
– Air that is less dense at higher altitudes absorb less
heat and thus temperature is lower
– Qn: Name some gases that would absorb heat.

23. FACTORS AFFECTING TEMPERATURE
• Distance from the sea
– The sea always heats up and cools down more
slowly than land
– This creates differences in rate of heating between
coastal and inland areas
– Places that are located along the coasts experience
Maritime effect
– Places that are located further inland experience
Continental effect

24. FACTORS AFFECTING TEMPERATURE
• Continental Effect
– The effect of continental surfaces on climate of
inland areas
– Inland areas are further from the sea and oceans
– These areas are not influenced by the
temperatures over the sea
– Inland areas tend to have warmer summers and
colder winters
– The annual temperature range is thus larger

25. FACTORS AFFECTING TEMPERATURE
• Cloud cover
– Refers to the extent of sky that is covered by
clouds
– More cloud cover results in a smaller diurnal range
– Less cloud cover results in a larger diurnal range
– This is due to the effect of clouds absorbing and
reflecting the sun’s rays and heat energy from the
earth’s surface (pg 77, fig 2.9)

26. TEMPERATURE
• DISCUSS
– Qn: Why do different places along the same
latitude have different temperatures?
• EXERCISE
– Textbook page 79
– Questions 1, 3 and 6 Group Work
Groups of 5
please

27. RELATIVE HUMIDITY
RELATIVE HUMIDITY =
Actual amount of water vapour in the air
--------------------------------------------------------------- X 100
Max amount of water vapour the air can hold

28. RELATIVE HUMIDITY
• Relative humidity is the ratio between
the actual amount of water vapour and
the maximum amount of water vapour
that the air can hold at a given
temperature
• Warmer air can hold more water vapour
• If temperature rises and the actual
amount of water vapour remains, then
relative humidity will decrease

29. RELATIVE HUMIDITY
• Saturation is when relative
humidity = 100%
• Dew point temperature:
temperature at which saturation
occurs
• Condensation occurs during dew
point temperature

30. CLOUDS
• Clouds refer to visible masses of water droplets or ice
crystals suspended in the atmosphere
• Evaporation: water becoming water vapour
• When water vapour rises, it cools to dew point
temperature
• Condensation: water vapour changes to liquid form
• To condense, water vapour needs to find condensation
nuclei
• Coalescence: water droplets bumping into each other to
become larger in size

31. Cloud making experiment
• We’ll do an experiment now to make clouds
• Let’s recap the key elements of a cloud.
– Water vapour
– Rapid condensation
– Pressure loss

32. Let’s watch the clip first

33. Let’s do it ‘live’
• Equipment check
1. Plastic bottle
2. Rubbing alcohol
3. Bicycle pump

34. Recap
• Sudden condensation leads to formation of
clouds by water vapour.
• Clouds are liquid form of water that have
condensed.
• If there is added pressure, the water vapour
reverts to it’s gaseous form.

35. RAINFALL
• Precipitation: water falling from the atmosphere
to the earth surface in any form
• E.g. Hail, Snow, Sleet, Rain…
• In tropics, the precipitation is mainly rain
• Air stability: a parcel of air that is cooler than its
surrounding air and tends to sink and remain in
its original position
• Air instability: a parcel of air that is warmer than
its surrounding air and tends to rise and expand
• 2 types of rainfall: Convectional and Relief

36. RAINFALL
• Convectional Rain
– Occurs due to intense heating of earth’s
surface
– Warm surface heats the air above it
– Instability causes air to rise and expand
– As air rises, it cools to dew point temperature
– Condensation occurs and clouds are formed
– When water droplets become large enough,
they fall as rain
– Convectional rain is often associated with
lightning and thunder
– Intense rain over a short amount of time

37. RAINFALL
• Relief Rain
– Also known as Orographic rain
– As air passes over the sea, it picks up moisture
– When it arrives at the coast, moist air is forced to
rise along the windward side of the mountain
– Air is forced to cool and condensation occurs at
dew point temperature
– When water droplets in the clouds become heavy
enough they fall to the ground on the windward
side
– On the other side of the mountain, leeward side, it
is dry as most of the moisture is lost on the
windward side (rain shadow)

38. RELATIVE HUMIDITY, CLOUDS &
RAINFALL
• DISCUSS
– What is the most common type of
rainfall in Singapore? Why do you say
so?
• EXERCISE
– Textbook page 82
– Questions 1, 2, 3 and 5

39. PRESSURE & WINDS
• Air pressure: the forced exerted by the weight
a column of air on a unit area of the earth’s
surface
• Measured in millibars (mb) by a barometer
• Air is less dense at higher altitudes
• Thus air pressure tends to be lower as altitude
increases
• The average value of air pressure at sea level is
1,013mb

40. PRESSURE & WINDS
• Wind: The movement of air from high
pressure area to low pressure area
• Pressure gradient: The difference in air
pressure between two places
• The greater the pressure gradient, the
higher the wind speed
• Wind can be described by its speed,
direction and frequency.

41. PRESSURE & WINDS
• Wind speed: The rate at which air is moving
• Wind speed is measured in kilometres per hour,
using an anemometer
• Wind speed may also be represented by the
Beaufort Scale (pg 85, figure 2.23)

42. PRESSURE & WINDS
• Wind direction: The direction which the wind
blows from
• Wind direction is measured by a wind vane
• Wind frequency: The percentage of time the
wind blows from a particular direction
• Prevailing winds: Winds that blows most
frequently from a specific direction
• Information of wind direction and frequency can
be recorded using wind roses

43. PRESSURE & WINDS
• Wind systems is a way of categorising prevailing
winds
• Localised wind systems
– Land breeze
– Sea breeze
• Regional wind systems
– Monsoon Winds
– Mid-latitude Westerlies
– Polar Easterlies

44. PRESSURE & WINDS
Land and Sea Breezes
• Local wind systems that occur along coastal
areas due to different rates of heating between
the land and sea
• Recall how temperature is affected by distance
from the sea
• In the night
– Land loses heat faster than the sea
– Warm air above the sea rises, creating
low pressure
– Air from the land moves towards the
sea as land breeze

45. PRESSURE & WINDS
Land and Sea Breezes
• In the day
– Land heats up faster than the sea
– Warm air above the land rises,
creating low pressure
– Air from the sea moves towards the
land as sea breeze

46. PRESSURE & WINDS
Monsoon Winds
• A regional wind pattern
• Brings seasonal changes in precipitation
• Affected by Coriolis effect
• Northern hemisphere -> deflects to the right
• Southern hemisphere -> deflects to the left
• Coriolis effect is stronger nearer the poles and
weaker near the equator

47. PRESSURE & WINDS
Monsoon Winds
• For purposes of study, we will use the monsoon winds
blowing between Asia and Australia as an example
• You should keep the following background knowledge that
you ALREADY HAVE…
– Summer = Higher Temp, Winter = Lower Temp
– High Temp = Low pressure, Low Temp = High
pressure
– Concept of relief rain and rain shadow
– Coriolis Effect: North = Right and South = Left
• Are you ready?

48. PRESSURE & WINDS
Southwest Monsoon (pg 88, figure 2.26)
• June to September
• Summer in northern hemisphere, winter in southern
hemisphere
• Winds move from Australia (south) to Asia (north)
• From Australia, wind moves as southeast monsoon
• As it crosses the equator, it deflects to become
southwest monsoon
• The air picks up moisture over Indian Ocean and
brings heavy rain to India

49. PRESSURE & WINDS
Northeast Monsoon (pg 88, figure 2.27)
• October to February
• Summer in southern hemisphere, winter in northern
hemisphere
• Winds move from Asia (north) to Australia (south)
• From Asia, wind moves as northeast monsoon
• As it crosses the equator, it deflects to become
northwest monsoon
• The air picks up moisture over Indian Ocean and
brings heavy rain to Australia

50. PRESSURE & WINDS
• DISCUSS
– How does the NE and SW monsoon
winds affect Singapore in terms of
rainfall?
• EXERCISE
– Textbook page 89
– Questions 2 and 4

51. CLIMATIC SYSTEMS
• Blah blah

52. THINK ABOUT THIS…
GATEWAY 2: What is happening to the earth’s
climate?
• Why are we so concerned about carbon
footprints?
• blahblah
• More questions from you?