Weather influences every part of our daily life. Climate shapes our culture, our history and our civilization. The changes in wind, temperature, humidity can not be underestimated.

3. WEATHER
• State of atmosphere at a local level and within a shorter
timescale
• Can be minutes – month
• Emphasis: Sunshine, Cloud, Win, rainfall, temperature

5. CLIMATE
• The long-term behavior/variations of the state of the
atmosphere/ patterns of weather in a larger region over a
longer period of time
• Usually over 30 years
• Average temperature, average precipitation, pressure,
vegetation, regular wind

10. EXOSPHERE
690 – 10000 km
Particles moving to
and from space
Lower boundary:
Exobase

11. THERMOSPHERE
• 85 – 690 km
• Temperature increasing with
height
• Low Air Pressure – thin air
• Electronically charged particles
will interfere with radio
broadcast
[Aurora/ North/ Southern Light
created by charged particles
and earth’s magnetic field]
• Air too thin for temperature to
be rightly detected

12. MESOSPHERE
• 50 - 80 km
• Boundary: Mesosphere
• Temperature drops with height
• Meteors burn up here – shooting stars

13. STRATOSPHERE
• 16 – 50 km
• Ozone layer is here
• Volcanic gases can affect
the climate
• Temperature increases
with height
• Ozone absorbs heat –
hence the increase with
height

14. TROPOSPHERE
• Up to 16 km
• Tropopause – the boundary
• Temperature decreases with height
(A result of changing insolation and
The subsequent heating of the air near
Ground surface)
Pressure
• Wind speed increases with height
• Weather occurs here – water vapor, dust particles,
clouds, rains, pollutants

16. 1. EARTH SUN GEOMETRY
• The earth’s revolution is elliptical
• The part of the elliptical plane closest to the sun:
Perihelion (147300000 km)
• The part of the plane with the longest distance from the
dun: Aphelion (152100000)
• The earth is tilted by about 23o – remains in such way
throughout the entire revolution – no change of tilts
PerihelionAphelion
Summer Solstice
Winter Solstice
Vernal Equinox
Autumnal Equinox

17. SEASONS – SOLSTICE/ EQUINOX
• The 4 seasons variation only exist in certain areas in the
world
• When one refers to Spring, Summer, Autumn, Winter – the
time periods are different between the 2 hemisphere
• Also seasons do not exist very much near the tropic or at
the poles

18. SEASONAL VARIATIONS
• Notice in the diagram below:
1. The earth is permanently tilted in one way – Axis parallelism
2. The earth doesn’t rotate in the way that the tilted side always face the
sun
3. The variation in points of solar reception occurs because the earth is
tilted in such way
Study the diagram below until you understand this fully
Video to help: https://www.youtube.com/watch?v=hHyQQ8UlXPk
https://www.youtube.com/watch?v=X8oGfa8VKtc

19. Perihelio
nAphelion

20. DRS
(Direct ray
of the sun)

21. DRS
(Direct ray
of the sun)

22. DRS
(Direct ray
of the sun)

23. THE DIFFERENT SEASONS
1. Summer Solstice: Summer in Northern hemisphere – winter in the
Southern Hemisphere - still hot in the tropic region – Arctic Circle
sunlight for 6 months – Antarctic circle no sunlight for 6 months
2. Autumnal Equinox: Direct Ray on equatorial region – Autumn in the
Northern hemisphere – Spring starting out in the Southern hemisphere
3. Winter Solstice: Winter in the Northern Hemisphere – strong summer in
the Southern hemisphere (Perihelion) – still hot in the tropic region –
Arctic Circle no sunlight for 6 months – Antarctic circle sunlight for 6
months
4. Vernal Equinox: Direct Ray on equatorial region – Spring in the Northern
hemisphere – Autumn in the Southern hemisphere

25. THE EARTH IS SOLAR POWERS
• All of the earth’s energy derives from the sun
• The absorbed solar power:
… Photosynthesis
… Evaporation
… Melting process
… Warms the earth

26. THE HEAT ENGINE
• The engine is responsible for balancing the energy
received from the sun and those radiating back
• ALS0!
• The energy reception of the earth is not evenly
distributed
• The equator receives the highest amount of sunlight
• The polar region receives the lowest

27. THE EARTH CAN NOT HEAT UP INFINITELY
• For all the energy received – the earth has to give back an
equal amount
• The outgoing radiation of the earth must be in a state of
radiative equilibrium with the energy received
• The heat engine of the earth is responsible for this

29. THE HEAT ENGINE
• The Heat engine also work to redistribute the energy around the surface
of the earth
• Achieving this through:
• Wind
• Convection
• Surface water
• Rainfall
• Ocean circulation/ currents

32. COMPONENTS OF THE DAYTIME ENERGY
BUDGET
• Insolation
• Reflected Solar Radiation
• Absorption
• Long Wave Radiation
• Latent Heat Transfer
• Sensible Heat Transfer

33. DAYTIME ENERGY BUDGET

34. 1. INSOLATION
• Incoming Solar Radiation
• Main Energy input in the system
• Affected by: Latitude, Season, Cloud Cover

35. 2. REFLECTED SOLAR RADIATION
• Proportion of energy reflected back = Albedo
• Albedo expressed as a percentage to the amount of
energy received from insolation
• Varies with color of the surface

36. 3. SURFACE ABSORPTION
• Energy that has the potential to heat up the surface
• Depends on the nature of the earth surface
• Some materials can conduct heat to a lower level e.g.
Water
• Other materials are poor conductor – heat concentrated
on the surface e.g. rocks

37. 4. LONG-WAVE RADIATION
• Radiation from the earth surface into the atmosphere –
some of which may go into space, some reflected back by
the atmosphere, some absorbed by the atmosphere
• There is also downward movement of radiation from
atmosphere
• The difference between the downward/upward movement
of radiation = net radiation balance

38. 5. LATENT HEAT TRANSFER
• Latent is the amount of heat energy needed to change the state of the
substance without changing its temperature
• Melting, Evaporation --- uses up the heat energy by 2238 Joules
• Such absorption of heating – cools the atmosphere
• Condensation, Sublimation – releases heat energy by 336 joules

39. 6. SENSIBLE HEAT TRANSFER
• Movement of air parcels in and out of a certain area
• Wind, convection
• Warm air rises, Cold air sinks
• Pressure gradient causes movement of air

40. NIGHTTIME ENERGY BUDGET

41. 1. SUB SURFACE SUPPLY
• Heat absorbed by rocks during the day form a supply of
heat
• This may be released during night time
• Compensates the cooling effect of nighttime

42. 2. NET RADIATION
• Radiation of energy from the earth is dominant in the
process of heat loss
• There is no insolation – earth just loses heat by long
wave
• In cloudless night – there is less downward radiation
• Cloudless night = large energy lost = colder

43. 3. LATENT HEAT
• Cooling effect at night causes cooling of the surface
• Warmer air on cool surface may result in condensation
• Condensation will release heat by 336 J
• Compensates for the cooling effect of the night time

44. 4. SENSIBLE HEAT TRANSFER
• Movement of wind in and old of the area
• May be land – sea breezes

46. 1. ASPECT
• Hillsides – change the angle at which the sun’s ray is
received
• Northern hemisphere – South facing slope (Ubac)
receives more sun ray
• Southern hemisphere – North facing slope (Adret)
receives more sun ray

47. 2. CLOUD COVER
• Reduces both incoming/outgoing solar radiation
• Thick cloud – greater amount of
absorption/reflection/scattering
• Therefore cloud reduces daytime energy (reflecting,
absorbing and scattering insolation)
• But it increases nighttime energy (absorbs/ reflects back
long-wave radiation from ground up)
• Therefore – the climate of deserts

49. 3. URBANIZATION
• Changes the albedo – dark concrete reflects more light
• Heat Island effect

51. WHAT DO WE KNOW FROM PREVIOUSLY
(SUMMARIZED)
1. The earth receives all of its energy from one input – Incoming Solar
Radiation (Insolation)
2. The out put from the global system is in the form of outgoing long-wave
radiation
3. The Insolation may be reflected/absorbed by the atmosphere
4. The Insolation may also be reflected by the earth surface
5. Number 3 and Number 4 are the limits of the Insolation received
6. However, the amount of insolation received varies between different
regions
7. This is due to Latitude, altitude, Solar constant, heat absorption, heat
reflection(albedos) , amount of gases in the atmosphere
8. Overall, the equator receives the most insolation
9. The polar receives the least insolation and reflected back most of it too
10. Therefore, most of earth’s energy is concentrated to 0 degree latitude
11. Hence the earth’s heat engine works to redistribute the energy evenly
across the surface
12. To put it absolutely simple: The Heat Engine = Weather conditions

52. FACTORS AFFECTING INSOLATION
• The Solar Constant: The amount of energy radiated to earth by the sun
– this is usually constant – affects very long term climate
• Distance from the sun (Elliptical orbit – perihelion - aphelion) – Annual
variation
• Latitudes: Heat has to go through more atmosphere in the polar and is
spread out over larger areas in the polar
• Length of nights/ days – years/ points on the earth surface

53. HEATING IMBALANCES
• Throughout the year – heating in different areas change
• This is due to the earth’s elliptical orbit
• However the differences between the heating imbalances of different
regions (Equator, tropics, poles) of the earth is actually caused by the
tilted axis

54. INSOLATION/ ABSORPTION/ REFLECTED SOLAR
RADIATION

55. UNDERSTAND THAT THE HEATING IMBALANCE PLAYS
HUGE ROLE IN DRIVING THE HEAT ENGINE – SINCE IT
INSPIRED THE HEAT TRANSFERS:
LATENT HEAT TRANSFER
(CLOUD/PRECIPITATION/DEW/FOG)
SENSIBLE HEAT TRANSFER
(SURFACE WIND/ HURRICANES/ CYCLONES/ OCEAN
CURRENTS)

56. HEIGHT ABOVE SEA-LEVEL
• REMEMBER: Atmosphere is not warmed by the sun – but
by radiation from the earth surface + distribution through
conduction/ convection
• Higher area – less land present – less heating effect
• Reduction in air pressure – less likely to hold heat

57. LAND-SEA DISTRIBUTION
• Sea is more transparent –
reflects less heat
• Sea can absorb heat to deeper
level
• Can transfer heat to greater
depth with convection
• The sea has a higher specific
heating capacity
• Sea requires more energy to
heat up a same amount of area
to land
• Hence sea heats up more
slowly
• In winter: Sea also loses
energy more slowly –
THERMAL RESERVOIR
• Coastal environment has
smaller temperature range

58. PREVAILING WIND
• Wind of different temperatures change the temperature of
the receiving areas
• Wind from the mountain – usually cold
• Wind from the sea – warmer in the winter, colder in the
summer

59. OCEAN CURRENTS
• Different areas of the ocean have different temperatures
• Near to the equator the sea is warm
• To the pole, the se is cold
• Warm ocean current carries warm water poleward and
cold water to the equator
• The ocean current is influenced by the prevailing wind
• The ocean conveyor belt also plays a part
• See all these in details in later section

62. HORIZONTAL HEAT TRANSFER
• Heat is transferred away from the tropic
• Prevents the equator from getting too cold
• Warms up the poles
• 80% - Wind
• 20% - Ocean Currents

63. VERTICAL HEAT TRANSFER
• Most radiative cooling occurs at the earth’s atmosphere
• Most insolation heating occurs at the earth’s surface
• Prevents earth’s surface from getting too hot
• Radiation
• Conduction
• Convection
• Latent Heat

65. ATMOSPHERIC MOISTURE
• Water in the atmosphere maintains life on earth
• Reflects/ scatters insolation
• Important in horizontal transfer
• Important in vertical transfer
• Latent heat transfer
• WATCH THIS:
https://www.youtube.com/watch?v=sP5ceNJTKVo

66. HUMIDITY
• Absolute Humidity: The mass of water vapor in a given volume of air
measured in grams per cubic meter (g/m3)
• Cold air can hold less water than warm air (cold air is denser)
• Relative Humidity: The amount of water vapor in the air at a given
temperature expressed as a percentage to the maximum amount of
water vapor the air can hold at that temperature
• When RH is 100% - air is saturated

67. DEW POINT
• If unsaturated air cools down where atmospheric
pressure is always constant– a DEW POINT will be
reached
• Dew point: The critical temperature where a specific
parcel of air becomes saturated
• Further cooling beyond the dew point = condensation
• Condensation at points below 0oC – snow

68. CONDENSATION RESULTS FROM COOLING
• 2 Types of cooling processes
• Radiative cooling
• Advection Cooling

69. RADIATION COOLING
• The land loses heat through outgoing long-wave
radiation
• The air in contact with the land is cooled by conduction
• Occurs in clear calm evening – no mixing of the air
• If air is moist – dew point is reached – forms RADIATION
FOG
• If temperature is below 0 – Hoar fog

70. ADVECTION COOLING
• Warm moist air move over a cooler land/ sea
• Warm air is cooled down to the dew point
• Fog is formed
• California/ Atacama desert (Warm air from land drifts over
cold ocean current)

71. SUBLIMATION
• When vapor condenses directly into ice crystals – doesn’t
pass through liquid state
• Condensation doesn’t quickly occur in clean air (lack of
hygroscopic nuclei)
• If the air is cold super clean air – it becomes SUPER
SATURATED
• It falls below its dew point without condensing
• They may go on to sublime

72. HYGROSCOPIC NUCLEI
• Particles that attract
water
• They act as
condensation nuclei –
encourages
condensation
• Important in fog
formation
• Volcanic dust (usually
result in condensation
into cloud then rain –
hence volcanic
eruption always result
in heavy rain)
• Dust from soil blown
by wind
• Urban industrial area –
smog/ Sulphuric acid

73. DEW
• Dew occurs with condensation
• Usually at dawn – as the temperature is still cool
• The colder earth surface cools down the air above it
• This causes vapor pressure to decrease as cold air can hold less water
vapor
• Eventually leads to condensation on surfaces – leaves, ground etc.
• Occurs in stable anticyclone condition – rapid radiation cooling

74. CLOUD TYPES

75. PRECIPITATION
1. RAIN
2. SNOW
3. SLEET
4. FROST
5. HAIL

76. RAINFALL
1. Convergent/ Cyclonic/ Frontal Rainfall
2. Orographic/ Relief Rainfall
3. Convectional Rainfall

77. CONVECTIONAL RAINFALL

78. OROGRAPHIC RAINFALL

79. FRONTAL RAINFALL

80. 2 THEORIES OF PRECIPITATION
Collision/ Coalescence theory: Occurs at Topical Zones – raindrops of
different sizes are forced into updraught at different rates

81. SNOW
• Forms like rain (2 theories of precipitation)
• Where temperature is under 0oC
• If hygroscopic nuclei present – ice crystals – which will
form snow flakes
• Since warm air can hold more moisture – It is best that
the air is JUST below 0oC and not very much colder

82. SLEET
• Mixture of ice and snow
• Forms when temperature is indeed below freezing point –
forming ice crystals
• However, lower layer is warm enough o allow partial
melting

83. GLAZED FROST
• Reverse of Sleet
• Water droplets at higher surfaces
• Freezes when passing through colder air
• May occur during temperature inversion

84. HAIL
• Frozen raindrop of more than 5 mm
• Forms with cumulonimbus cloud
• Uplift of air by convection current
• Uplift at cold front
• Hail falls through cumulonimbus cloud (he lower layer is
not warm enough to melt the hail because of latent heat
absorbed in evaporation)

85. TROPICAL CYCLONES
• Intense low pressure system – hurricanes, typhoons,
cyclones
• Found near equator, near the ITCZ
• Wind of extreme velocity
• Torrential rainfall
• Develop over warm tropical regions
• In autumn – highest sea temperature
• Trade wind belt
• Coriolis force needed for a ‘spin’ – hence not nearer to
the equator

86. ADIABATIC PROCESSES
• The cooling/ warming up of air in response to changes with altitude
• In the troposphere – temperature decreases with altitude
• In the upper area – air is less dense – allows for cooling
• Less and area – less surface absorption and hence less long wave
radiation
• So – temperature of air changes internally
• Diabetic process – involve mixing of air

87. LAPSE RATE
• An idea that the atmosphere reduces in temperature as it increases with
height at the rate of 6 degree Celsius per 1 km
• Air is a poor conductor of heat
• Air expands and rises – it uses up the energy in the process
• Air rising can be caused by:
1. CONVECTION
2. OROGRAPHIC UPLIFT
3. FRONTAL SYSTEM
4. TURBULENCE

88. LAPSE RATE
• Environmental Lapse rate: The general rate at which air decreases in
temperature: 6 degree Celsius/ 1 km
• Dry Adiabatic Lapse (DALR): Lapse rate of a dry parcel of air
• Saturated Adiabatic Lapse rate (SALR): Lapse rate of a saturated,
condensing air – is lower than DALR since saturated air will be
condensing and releasing energy hence slowing down the cooling
process
• The DALR and SALR are used with a specific parcel of air as compared
to the ELR which is the average of normal air
• WATHC THIS: https://www.youtube.com/watch?v=AVdNAlDyFR8

89. INSTABILITY
• When the ELR is greater than DALR
• When the air is warmed and it begins to rise
• Adiabatic cooling is still slower than the surrounding atmosphere
• At any given altitude, the rising air will still be warmer and it will
continue to rise
• Air will soon cools to a dew point and continue to cool at SALR – here
clouds will already have been formed
• Results in formation of clouds and precipitation
• With moist air – vertical cloud development

90. STABILITY
• When DALR and SALR are higher than ELR
• Which means the air at any given altitude will be cooling at a much
faster rate than the surrounding atmosphere and hence it will be cooler
and HENCE it will be sinking
• Uplift can not be sustained if at any point this air is cooler - even when
it is saturated
• This creates an anticyclone condition – subsiding air
• Stable can only rise when it’s forced to

91. CONDITIONAL INSTABILITY
• ELR is between DALR and SALR
• So if the air is dry – it cools faster and remains sinking
• If the air is saturated then it may be warmer than ELR
• If there is a case of orographic uplift or turbulence – there maybe
instability

93. WIND
• Wind are moving air masses both at the surface (surface wind) and in
the upper layer of the atmosphere.
• Wind is a result of the differences in pressure on the surface
• Air always moved from areas of higher pressure to areas of lower
pressure
• Watch this before continuing:
https://www.youtube.com/watch?v=Vjd87n4qIFE

95. OTHER FORCES ACTING ON WIND
• There are two other forces aside from pressure gradient that are
influence the direction and patterns of wind
1. Surface Friction
2. The Coriolis force
• Balance between the forces of pressure gradient and the Coriolis force
is called the Geostrophic forces
• The wind resulting from such force – Geostrophic wind

96. THE CORIOLIS FORCE
• Since the earth is rotating from
WEST TO EAST
• Any object moving north-south will
always be deflected to a direction
• Imagine a spinning disc – and you
roll a ball on it – the ball with
deflected to an opposite direction
because the ground underneath
the ball is moving
• Wind in the northern hemisphere
are deflected to the right
• Wind in the southern hemisphere
are deflected to the left
• I know it’s complicated… so watch
these videos.

97. FRICTION
• The drag exerted on the wind as it flows across the earth’s surface
• Mountains, terrains, urban areas – all causes friction
• Friction can reduce the effect of the Coriolis force at the surface

98. WATCH THE FOLLOWING VIDEO TO
UNDERSTAND DIFFERENT PRESSURE
GRADIENT
https://www.youtube.com/watch?v=oCdqGkn-B1E
https://www.youtube.com/watch?v=8ixT7D3f8Qo
https://www.youtube.com/watch?v=O4x_DVSseIk

99. THE TRICELLULAR MODEL
• After watching the video, you will be able to understand that
the unequal solar heating of the earth surface first causes
differential pressure.
• The differential pressures are the major cause for air
movement and wind
• The model you saw in the videos previously could be
referred to as the Tricellular model
• Simply stated, it is a model divided into three cells: The
Hadley, the Ferrell and the Polar.

100. THE THREE CELLS
• These 3 cells exist in pairs
• Basically the North and the Southern hemisphere echoes each other
• They both have 3 cells which are identical to each other.
• Imagine the equator being a mirror

101. THE HADLEY CELLS
• Let’s imagine the air masses of the equator as
a single parcel (which they absolutely are not)
• Maximum solar radiation at the equator =
maximum heating
• That air parcel expands – lower density – air
parcel rises – creating a low pressure belt
• It reaches the tropopause – where it diverges
into two – one flows beneath the tropopause to
just above the 30 degree latitude north the
other to the Southern equivalent
• At which point the air has been cooling enough
that it has became denser
• Now it sinks at 30 degree – creating a high
pressure belt
• At the surface – air moves from the high
pressure belt to the low pressure belt DOWN
the concentration gradient
• The air is returned to the equator in the form of
trade wind
• At the equator – air from the two high pressure
belts converge in the ITCZ (Inter Tropical
Convergence Zone)
• Here it rises once again
• WE HAVE A CONVECTION CELL!
https://www.youtube.co
m/watch?v=kRdiMqUBj
gM

104. THE FERRELL CELLS
• At 30 degree high pressure areas (aka the
Subtropical High Pressure belts) – sinking air
diverges into 2 types of surface winds
• One of which we know are the trade winds
flowing to the ITCZ
• The other type is the what we will be calling
the westerly
• We will explore these winds in a second, but
for now, concentrate on the new developing
cells
• So a stream of surface wind flows from the
STHP (Sub Tropical High Pressure belt) at 30
degrees to the 60 degree
• At 60 degrees the wind converges with
another set of wind flowing down from the
pole, once again down the pressure gradient
because the pole is cold and hence air there
will be dense
• SO… Convergence of air here causes air to
rise at 60 degrees
• We therefore call this belt the Sub Polar Low
Pressure Belt (SPLP)
• Our air from the STHP now rises here, hitting
the tropopause – flowing back to the 30
degree STHP where it sinks at 30 degree after
cooling
• WE HAVE THE FERRELL CELL!

105. THE POLAR CELL
• Air sinks at the 90 degree poles – creating a high pressure region
• This is probably the coldest areas in the world because of low angle
from the sun and high albedo
• Air naturally moves across the surface to 60 degree SPLP (Sub Polar
Low Pressure Belt)
• Once again, a convergence
• Air rises – diverging at the tropopause
• A specific mass travels to the Pole where it sinks back down again
• This is our Polar Cell

106. INTER TROPICAL CONVERGENCE ZONE
• The ITCZ
• Locations of the Doldrums/ the equatorial trough
• Her the surface wind converges inward – there may be area where ships
can not move because of the gap between the 2 converging streams of
wind (the doldrums)
• Rising air here releases latent heat with condensation – stimulates
convection
• A lot of tropical rainforest
• Latitudinal variation – changes in overhead sun
• June: this moves north – in December it moves south
• It goes where the summer si
• Over the sea there is less variation – because sea has higher specific
heating capacity and rarely change in temperature

107. JET STREAMS/ ROSSBY’S WAVE
• These are currents of moving air at the upper layers of the atmosphere
• It is through the discovery of the Jet Streams/ Rossby wave in the 1940s
that allow Rossby himself to create the Tricellular model
• The Jet streams and the Rossby wave help mix the air at the upper layer
and assist in the transfer of heat from the equator to the Poles

108. JET STREAMS/ ROSSBY WAVES
• Jet Streams are caused by differential air masses
• There are 2 streams – the Sub Tropical and the Polar
• They also meander in a wave called Rossby Wave
• The energy of the Ferrell cell is actually obtained by the transfer of heat
in the upper layer of the atmosphere by the Jetstream