2. You will learn…
- to compare the difference between weather and climate
- to describe the elements of weather
- to explain the factors influencing temperature
- to explain why relative humidity is different at different
locations
- to explain how rain and winds are formed
3. Weather and Climate
•Weather refers to the conditions of the
atmosphere at a specific place over a relatively
short period of time.
• Climate refers to the atmospheric conditions of a
specific place over a considerable period of time,
usually 30 to 35 years.
• Climate remains largely unchanged, but weather
may change from day to day.
4. Elements of Weather
Weather is described by referring to its elements:
Temperature
Relative humidity
Precipitation
Pressure and winds
5. Temperature
The degree of hotness and coldness of a place
Affected by solar radiation reaching the Earth’s
surface
Amount of solar radiation is determined by:
Latitude
Altitude
Distance from sea
Cloud cover
6. Factors Influencing Temperature
• Latitude: the distance (in degrees) to the north and south
of the Equator
Temperatures at the Poles and the Equator are different because
the Sun’s rays travel different distances and strike the Earth’s
surface at different angles.
7. Factors Influencing Temperature
• Latitude
• The Poles (high latitudes)
experience lower temperature
because solar radiation is spread
over a larger area, as compared to
regions near the Equator (low
latitudes).
• The Sun’s rays also travel a
greater distance to reach regions
near the Poles, hence they are
less intense, and temperatures are
lower.
8.
9. Kibo Summit of Kilimanjaro
Elevation 5,895 m (19,341 ft)[1]
Prominence 5,885 m (19,308 ft)[2]Ranked 4th
11. Factors Influencing Temperature
• Altitude: the height of a point above the sea
level
Normal Lapse Rate: On average, temperature
falls by about 6.5°C for every 1 000 metres
increase in altitude.
12. Altitude
Snow Cap
Sea Level
Tree Line
* Altitude impacts if over 5,000 ft*
Burr,
it’s
getting
cold!
13. Factors Influencing Temperature
• Altitude
• Places near the sea level (low altitude) are
warmer because the Earth’s surface absorbs
heat from the Sun directly.
• Air at high altitudes is thin and is unable to
absorb heat as effectively as dense air because it
has smaller concentration of gases to trap heat.
14. When the atmosphere absorbs longwave radiation, the sun’s solar energy is
trapped and this warms the earth.
Air closer to the surface absorbs more heat than air at higher altitude.
15. 3. Distance from the sea
Land heats and cools faster than the sea. Coastal areas have a lower temperature
than inland areas. On the coast winters are mild and summers are cool. In inland
areas temperatures are high in the summer and cold in the winter.
16. Factors Influencing Temperature
• Distance from the sea: the difference in the rate of heating
and cooling of land and sea has an effect on the temperatures
of coastal areas.
Land heats up and cools down more quickly than
the sea.
19. Factors Influencing Temperature
• Near to the sea – Maritime effect
Coastal areas experience cooler summers and warmer winters.
These places have a smaller temperature range at an annual
scale.
Land Sea
Summer Air heats up
quickly
Air gains heat
slowly
Winter Air loses heat
quickly
Air loses heat
slowly
20. Factors Influencing Temperature
• Far from the sea – Continental effect
Inland areas experience warmer summers and cooler
winters.
These places have a larger temperature range at an
annual scale.
Land
Summer Air heats up quickly
Winter Air loses heat quickly
21. Factors Influencing Temperature
• Cloud cover: the amount of clouds over an area.
Places with more cloud cover experience a smaller
difference in day and night temperatures.
Places with less cloud cover experience a larger
difference in day and night temperatures.
Presence of clouds Absence of clouds
Day Less solar radiation
absorbed by land
More solar radiation
absorbed by land
Night Less heat escaping into
outer space
More heat escaping into
outer space
24. Absence of cloud cover
• During the day, large amount of sun’s energy reach the
earth and heats the earth’s surface quickly.
• During the night, heat escapes easily from the earth’s
surface into space and makes the land cooler.
25. Humidity
• Humidity is the amount of water vapor in the air. Water
vapor is the gas phase of water and is invisible.[1] Humidity
indicates the likelihood of precipitation, dew, or fog.
27. Relative Humidity
The proportion of water vapour
present in the air, in relation to the
maximum amount the air can hold
at a particular temperature
Expressed as a percentage
Saturation occurs when the air
carries the maximum amount of
water vapour it can hold at that
temperature (i.e. relative humidity
at 100%).
28. Relative Humidity
High relative humidity indicates rain is
likely to occur.
Thus, temperature and relative humidity
is closely related to precipitation.
Desert regions have low rainfall
and low relative humidity.
High rainfall and high relative humidity
promotes growth of thick vegetation.
29.
30. Video on relative humidity
• http://www.youtube.com/watch?v=CL5cgXwKUXc
31. Precipitation
Water falling from the atmosphere onto the Earth’s
surface, i.e. rain, snow, frost or hail
Form of precipitation depends on the temperature
of the place where it falls
Precipitation in the form of rain. Precipitation in the form of hail.
32. Dark rain clouds hang over the financial
skyline in Singapore in March.
33. Watch a video!
• http://www.youtube.com/watch?
v=RkgThul2El8andfeature=player_embedded.
• http://www.youtube.com/watch?v=TYM1Orx3G3E
34. Convectional rain – very common in
tropical regions
Air above the ground gets heated and
rises.
Air cools and condenses as it rises
above saturation point (100% relative
humidity).
Clouds are formed and falls as rain
when the water droplets become too
heavy.
35. As the environmental condition
becomes cooler at higher altitude,
water vapour cools to form
microscopic water droplets that
are suspended in the air. These
water droplets form clouds.
As the environmental
condition becomes
warmer, water near the
surface will heat up and
transform into water
vapour. As a result, the
water vapour will ascend
and rise in altitude.
Evaporation
Water Body
(Water in liquid state)
Condensation
Saturation
As the environmental condition
becomes cooler at higher altitude,
water vapour cools to form
microscopic water droplets that
are suspended in the air. These
water droplets form clouds.
As the environmental
condition becomes
warmer, water near the
surface will heat up and
transform into water
vapour. As a result, the
water vapour will ascend
and rise in altitude.
Atmosphere
As more and more water
vapour rises and
condenses, the parcel of
air becomes saturated .
Precipitation
With presence of
condensation nuclei such
as dust, the water droplets
will coalesce to form
bigger and heavier water
droplets that will fall to the
ground as rainfall. This
process is known as
precipitation.
rainfall
Annotation- Formation of Convectional Rain
36. Precipitation
• Relief rain – occurs in places with highland near
water bodies
Air from a sea or a large lake carries larger amounts of water vapour.
As moist air is blown towards a mountain range, the air is forced to rise,
cool and condense.
Clouds are formed and falls as rain when the water droplets become too
heavy.
Relief rain falls mainly on the windward side of the mountain whereas
the leeward side of the mountain remains relatively drier.
38. Sea
Mountain
Moist air from
the
Moist air condenses to form clouds
Lower
temperature at
higher altitude
cools ascending
moist air
quickly
Mountain as barrier
Moist air
forced to
ascend
As the water
droplets
become larger
due to
concentration
of moist air,
rainfall will
result.
39. Pressure and winds
• Air pressure (atmospheric pressure): the downward force
exerted by the weight of air per unit area on the Earth’s surface
Low pressure occurs when altitude is higher.
Gravity is less resulting in decrease in the concentration of gases.
Air molecules are far apart and air becomes thinner. Therefore weight of
the air falls.
High pressure occurs when altitude is lower. Air molecules are closely
packed and air becomes denser.
40. Pressure and winds
• Wind: the horizontal movement of air from a region of high
pressure to a region of low pressure
Cool air sinks; high pressure
area formed at low altitude.
Warm air rises; low pressure
area formed at high altitude.
Movement of air mass from high pressure
HP area to low pressure area. LP
41. Pressure and winds
• Sea breeze: cooling effect on coastal areas
in the day.
Cool air over sea (high pressure) replaces
warm air on the land (low pressure).
• Land breeze: wind that blows from the land
to the sea.
Land loses heat faster than the sea at night.
Cool air over land (high pressure) replaces
warm air over sea (low pressure).
45. Pressure and winds
• Large-scale (monsoon) winds: seasonal
movements of large air masses across the
Earth, as the Northern and Southern
Hemispheres experience different seasons.
Caused by the extreme heating and cooling of
large landmasses.
Winds are deflected on mo
Earth due to the Coriolis effect.
46. MMOONNSSOOOONNSS
• Large-scale seasonal winds that are
characterised by a seasonal reversal of wind
direction
• Caused by huge land masses & seas having
different rates of heating up & cooling down
• Common features of climates of South,
Southeast & East Asia
• Causes heavy rains, strong winds &
sometimes floods
55. MMOONNSSOOOONNSS
• Monsoon winds are seasonal movements of
large air masses across the earth.
• These winds occur in South Asia and
Southeast Asia.
• Caused by extreme heating and cooling of
large landmasses.
• June to September: Northern Hemisphere
experience summer while Southern
Hemisphere experiences winter.
•Warm air is less dense than cold air an area of
low pressure develops over the Indian
subcontinent while an area of high pressure
develops over the Australian continent.
• Southwest winds blow over the Indian ocean.
It picks up moisture and brings heavy rain to
Southwestern India and Bangladesh.
56. Northeast Monsoon
Northern Hemisphere
• Land is colder than sea during winter
• High pressure area develops over continental Asia,
while low pressure area over the oceans
• Existence of greater low pressure area in Australia (in
Southern hemisphere experiencing summer)
57. Northeast Monsoon
Northern Hemisphere
• Thus, cold winds from interior of Asia blow towards
warmer areas of Australia (high to low pressure
areas)
• As they blow (move) towards the Equator deflected
to their right Blowing as northeasterly winds
Northeast Monsoons
58.
59. Pressure and winds
• Southwest Monsoon (June to September)
Summer in Northern Hemisphere and winter in
Southern Hemisphere.
Cold air from Australian continent (south; high
pressure) blows toward Indian sub-continent
(north; low pressure).
Winds are deflected to the right as they enter
into the Northern Hemisphere.
Moisture carried by the wind brings heavy rain to
southwestern India and Bangladesh.
60. Pressure and winds
• Northeast Monsoon (October to January)
Winter in Northern Hemisphere and summer in
Southern Hemisphere.
Winds from Indian sub-continent (north; high
pressure) blow toward Australian continent
(south; low pressure).
Winds are deflected to the left as they enter
into the Southern Hemisphere.
Winds blow across the Asian continent and are
cold and dry, bringing little rain to India and
Bangladesh.
62. 1. Based on your knowledge of Monsoon winds, explain
why there are few tourists in Pulau Tioman between the
months of October and January.
• October to January: wind is blowing from the northeast
across the South China Sea to Pulau Tioman.
• The wind picks up moisture from South China Sea.
• Northeast wind will bring heavy rain, strong winds and big
waves.
• Therefore, less tourist will visit the island.
63. Understanding the
Elements of Weather
• Helps prepare for whatever
weather conditions that may
occur.
• Allows the classification of the
world’s regions according to
different types of climate.
