- Factors Affecting Climate (Temperature, Rainfall, Relative Humidity, Air pressure, Winds, Clouds) - Factors Affecting Temperature (Cloud Cover, Latitude, Altitude, Distance from Sea)

1. Chapter 3
Weather & Climate
Gateway 1

2. Describe
the
weather
of
Singapore
over
the
last
three
days
How
would
you
describe
the
climate
of
Singapore?

3. How
then
is
weather
different
from
climate?
What
differen=ates
weather
from
climate?
MEASURE OF TIME
– Weather:
Short-­‐term
changes
(minutes
to
months)
– Climate:
Long-­‐term
weather
pa:erns
(30
years)

4. What
are
the
elements
of
weather?
a.
Temperature
b.
Relative
humidity
c.
Clouds
d.
Rainfall
e.
Air
pressure
and
wind

5. a.
What
influences
temperature?
(i)
Latitude
(ii)
Altitude
(iii)
Distance
from
sea
(iv)
Cloud
cover

6. (i)
La>tude
North Pole 90°N
longer distance through atmosphere
shorter distance through atmosphere
larger angle of incidence
smaller angle of incidence
atmosphere
sun’s rays are
concentrated over
a smaller area
sun’s rays are spread over a wider area
South Pole 90°S
Equator 0°
Tropic of Cancer
23.5°N
Tropic of Capricorn
23.5°S
∴ temperature
becomes higher
sun’s rays
sun’s rays
higher latitude
lower latitude

7. (ii)
Al>tude
higher concentration
of atmospheric gases
& particles to trap
the heat emitted from
the warm ground
lesser atmospheric
gases & particles
to absorb heat
incoming
solar energy
warms the
earth’s surface
earth’s atmosphere
more concentrated
nearer the
earth’s surface
longwave radiation
from the ground
earth’s atmosphere much thinner
further from the earth’s surface

8. (ii)
Al>tude
0m (ground)
Base: larger area of land to absorb heat
Peak: smaller area of
land to absorb heat
1,000m
2,000m
3,000m
4,000m
5,000m (higher altitude)
Altitude Temperature
-13°C
-6.5°C
0°C
6.5°C
13°C
19.5°Cdenser air
thinner air
Highland
temp
decreases
by 6.5°
with every
1000m
increase
in altitude

9. (iii)
Distance
from
sea
coastal areas
SUMMER
land heats up quickly
sea heats up slowly
cooler air over
sea lowers the
temperature of
coastal areas
air over sea becomes
relatively cooler
inland areas
sea
air over the land
becomes warmer than
the air over the sea
inland areas experience
warmer summers
coastal areas experience
cooler summers

10. (iii)
Distance
from
sea
coastal areas
WINTER
land cools quickly
sea cools slowly
warmer air over
the sea increases
the temperature
of coastal areas
air over the sea becomes
warmer than the air over land
inland areas
sea
inland areas
becomes colder
inland areas experience
colder winters
coastal areas experience
warmer winters

11. (iii)
Distance
from
sea
coastal areas
inland areas
sea• land heats up quickly
➙
warmer summers
• land cools quickly
➙
colder winters
• sea heats up slowly
• sea cools slowly
causes larger annual
temperature range
in inland areas
causes smaller annual
temperature range
in coastal areas
cooler summers
warmer winters

12. (iv)
Cloud
cover
less solar radiation
reaching the ground
thick clouds absorb & reflect
a large amount of incoming solar
radiation back into space
thick clouds absorb & prevent much
of the heat that is radiated from the
ground from escaping back into space
Day (30°C) Night (25°C)
earth’s surface is not heated
up excessively in the day
air near the earth’s surface is kept warm at night
as temperature falls by only a few degrees
Presence of cloud cover:
smaller diurnal temperature
range (less than 10°C)

13. (iv)
Cloud
cover
heat radiated from
the ground escapes
back into space
without interruption
Day (40°C)
earth’s surface becomes heated
up excessively in the day
air near the earth’s surface becomes cooler at
night as temperature falls by many degrees
maximum
incoming
solar
radiation
reaching
the ground
Night (10°C)Absence of cloud cover:
diurnal temperature range
as high as 30°C

14. a.
What
influences
temperature?
(i)
Latitude
(ii)
Altitude
(iii)
Distance
from
sea
(iv)
Cloud
cover
C.L.A.D.

15. What
are
the
elements
of
weather?
a.
Temperature
(C.L.A.D.)
b.
Relative
humidity
c.
Clouds
d.
Rainfall
e.
Air
pressure
and
wind

16. b.
Rela>ve
humidity
=
Actual
amount
of
water
vapour
in
the
air
Maximum
amount
of
water
vapour
the
air
can
hold
• RH
is
usually
expressed
in
percentage
(%)
x
100
Maximum
amount
of
water
vapour
the
air
can
hold
Actual
amount
of
water
vapour
in
the
air
at
a
par>cular
>me
(T1)
At
15°C
10g/m3 5g/m3

17. Where
does
water
vapour
in
the
air
come
from?
Evaporation
froM:
• ponds,
lakes
• seas,
oceans
• water
on
leaves
Transpiration
froM:
• vegeta>on

18.
What
affects
the
amount
of
water
vapour
the
air
can
hold?
Temperature
➙
affects
size
of
air
mass
amount of
water vapour
Air at 15°C Air at 25°C
air expands
when it
becomes
warmer
∴ its capacity to hold
water vapour increases.
10g/m3
20g/m3
✏
Warm
air
can
hold
more
water
vapour
than
cool
air.

19.
How
does
the
amount
of
water
vapour
affect
the
rela=ve
humidity?
Maximum amount
of water vapour the
air can hold
Actual amount of
water vapour in the
air at T1
At 15°C
Actual amount of
water vapour in
the air at T2
10g/m3
5g/m3 8g/m3
✏
The
higher
amount
of
water
vapour
in
the
air
at
a
par7cular
temperature,
the
higher
the
rela7ve
humidity.

20.
Let’s
put
the
same
mass
of
air
(5g/m3)
at
different
temperatures:
Maximum amount of water
vapour the air can hold
Actual amount of water
vapour in the air at T1
At 15°C
10g/m3 5g/m3
At 25°C
Maximum amount of water
vapour the air can hold
Actual amount of water
vapour in the air at T3
20g/m3 5g/m3
✏
Lowest
RH
occurs
during
7me
of
greatest
air
temp

21. Why
do
I
feel
more
humid
on
a
rainy
day?
At 25°C
20g/m3
Actual amount of
water vapour in the
air after the rain (T4)
Maximum amount
of water vapour the
air can hold
Actual amount of
water vapour in the air
before the rain (T3)
5g/m3
At 15°C
20g/m3
✏
Satura>on
occurs
when
RH
=
100%
✏
The
temp
at
which
satura>on
occurs
is
called
the
dew point temperature

22. What
are
the
elements
of
weather?
a.
Temperature
b.
Relative
humidity
c.
Clouds
d.
Rainfall
e.
Air
pressure
and
wind

23. c.
Clouds
③
When water droplets in the air bump
into each other, they coalesce and
become larger to eventually form clouds.
Dew point reached:
condensation begins
①
As water vapour rises, it cools.
Eventually, rising air cools to
dew point temperature.
The tiny particles
(eg. dust) in the air
are called
condensation
nuclei.
②
Water vapour condenses on tiny particles
present in the atmosphere to form water droplets.
ground
④
When the water droplets
become too large & heavy,
they fall to the earth’s
surface as precipitation
(eg. rain, hail)

24. c.
Clouds
Interes>ng
clouds

25. What
are
the
elements
of
weather?
a.
Temperature
b.
Relative
humidity
c.
Clouds
d.
Rainfall
(convectional
&
relief
rain)
e.
Air
pressure
and
wind

26. d.
Rainfall
Dew
Mist
Fog
Rain
Hail
Snow
different types
of Precipitation
main
form
of
precipita7on
in
the
tropics

27. d.
Rainfall
measure using:
– a
rain
gauge
(in
mm)
High rainfall:
– more
than
1,500mm
Low rainfall:
– less
than
250mm

28. d.
Rainfall
instable air:
– it
is
a
parcel
of
air
that
rises
instead
of
remaining
in
its
original
posi>on
• Hot air rises (unstable)
• cool air sinks
caused by
air instability

29. d.
Rainfall
Temp of air
parcel1
= 9.5 °C
Distance away
from the ground
Temperature of
surrounding air
100m
10°C
9.3°C
Parcel of air sinks and
remains near the ground
because it is cooler than
its surrounding air ➙
it
is a stable air parcel
Parcel of air expands
and rises as it is
warmer than its
surrounding air ➙
it is
an unstable air parcel
0m (ground)
Temp of air
parcel2
= 10.5 °C
Temp of air
parcel2
= 9 °C
The parcel of air stops
rising & remains at this
position because it is
now cooler than its
surrounding air ➙
it
becomes a stable air
parcel
• Hot air rises (∴unstable)
• Cool air sinks (stable)
Stable & unstable
air parcels

30. d.
Rainfall
①
Earth’s surface is intensely
heated up by the sun’s energy
②
Air above the
ground warms,
expands & rises.
③
As water vapour rises,
it cools. Eventually, air cools
to dew point temperature.
④
Cumulonimbus
clouds are often formedDew point reached:
condensation occurs
➙ clouds form
⑤
Water droplets in the
clouds eventually
become too large and
heavy. Thus, they fall
to the ground as
convectional rain.
Such rain is usually
accompanied by
thunder & lightning.
#1 Convectional rain

31. d.
Rainfall
#2 relief rain
Mountain
barrier
①
Moist air from the sea
is forced to rise up the
windward slope.
②
As air rises, it cools to the
dew point temperature. Thus, condensation
occurs & clouds form.
③
When water droplets in the
clouds become too large and
heavy, they fall as relief rain.
④
By the time the air moves down
the leeward slope, it is dry as most
of the moisture has fallen on
the windward side.
Thus, no rain falls on
the leeward side.
h:ps://
www.youtube.com/
watch?v=BVykQfRC_aI

32. What
are
the
elements
of
weather?
a.
Temperature
b.
Relative
humidity
c.
Clouds
d.
Rainfall
(convectional
&
relief
rain)
e.
Air
pressure
and
wind

33. e.
Air
pressure
and
winds
Air pressure:
– force
exerted
on
a
unit
area
of
the
earth’s
surface
caused
by
the
weight
of
a
column
of
air
above
it.
Air pressure @ sea level:
– 1,013millibars
(mb)
High air pressure:
– if
above
sea
value
(ie.
more
than
1,013mb)
Low air pressure:
– if
below
sea
value
(ie.
less
than
1,013mb)

34. e.
Air
pressure
and
winds
∴
sea level
(1,013mb)
Altitude
denser air
(∴ higher air pressure)
less dense air
(∴ lower air pressure)
Highland
higher altitude
(200mb)
larger
column
of air
∴ higher
pressure
Air is less dense at higher
altitudes because gravity
pulls air molecules towards
the surface of the earth.
lower altitude
(1,000mb)
smaller column of air
over a unit area

35. e.
Air
pressure
and
winds
measure pressure
using:
– a
barometer
(in
mb)
– millibars

36. e.
Air
pressure
and
winds
Isobars
– lines
joining
places
of
equal
air
pressure
Weather map / synoptic chart
– constructed
using
measurements
of
air
pressure

37. e.
Air
pressure
and
winds
High air
pressure:
– pressure
more
than
1,013mb
Low air
pressure:
– pressure
less
than
1,013mb
Air moves from
High to low
pressure areas

38. e.
Air
pressure
and
winds
pressure gradient
– difference
in
air
pressure
between
2
loca>ons
wind:
– movement
of
air
from
high
pressure
to
low
pressure
areas
wind speed:
– rate
at
which
air
is
moving
Faster wind speed:
– when
there
is
a
greater
difference
in
air
pressure

39. e.
Air
pressure
and
winds
measure wind speed using:
– an
anemometer
(in
km/hr)

40. e.
Air
pressure
and
winds
wind systems
– Sea
&
land
breezes:
• Sea
breeze
(day)
• Land
breeze
(night)
– Monsoon
winds:
• Southwest
monsoon
(between
Jun
&
Sep)
• Northeast
monsoon
(between
Oct
&
Feb)

41. e.
Air
pressure
and
winds
Sea and Land Breeze:
– formed
by
the
differences
in
air
pressure
due
to
the
different
rates
at
which
land
and
water
bodies
cool:
• Landà
heats
up
&
cools
down
quickly
• Seaà
heats
up
&
cools
down
slowly
h:p://www.classzone.com/books/earth_science/
terc/content/visualiza>ons/es1903/
es1903page01.cfm?chapter_no=visualiza>on

42. e.
Air
pressure
and
winds
Monsoon winds:
– large
scale
seasonal
winds
that
reverse
direc>on
seasonally
– causes
seasonal
changes
in
precipita>on
– monsoon
winds
&
other
winds
are
affected
by
Coriolis effect

43. e.
Air
pressure
and
winds
Coriolis effect:
– a
force
produced
by
earth’s
rota>on
– it
causes
the
bending
or
deflec7on
of
winds:
• northern
hemisphere
wind
deflects
right
• southern
hemisphere
wind
deflects
le<
– it
is
strongest
@
the
poles;
– it
is
weak
@
the
tropics;
and
– it
is
not
felt
@
the
equator

44. e.
Air
pressure
and
winds
Equator 0°
30°S
30°N
60°N
60°S
South Pole 90°S
North Pole 90°N
(low pressure)
(high pressure)
(high pressure)
(low pressure)
(low pressure)
(high pressure)
(high pressure)
Air moves from
a zone of
high pressure
to low pressure

45. e.
Air
pressure
and
winds
Equator 0°
30°S
30°N
60°N
60°S
South Pole 90°S
North Pole 90°N
In the northern
hemisphere, winds
are deflected to the
right due to the
coriolis effect
In the southern
hemisphere, winds
are deflected to the
left due to the
coriolis effect
(low pressure)
(low pressure)
(low pressure)
(high pressure)
(high pressure)
(high pressure)
(high pressure)

46. e.
Air
pressure
and
winds
Monsoon winds:
– caused
by
the
different
rates
of
hea>ng
up
&
cooling
down
of
huge
land
masses
&
seas
– this
creates
difference
in
air
pressure
between
land
masses
&
seas
– this
results
in
the
movement
of
large-­‐scale
winds
from
high
pressure
to
low
pressure
areas

47. What
are
the
elements
of
weather?
a.
Temperature
b.
Relative
humidity
c.
Clouds
d.
Rainfall
(convectional
&
relief
rain)
e.
Air
pressure
and
wind
T.R.R.A.C.