© Oxford University Press 2009 Part 7 Global warming─Are humans responsible? Quit 7.2What is the normal global distribution global distribution pattern.

© Oxford University Press 2009

Part 7 Global warming─Are humans responsible?

Quit

7.27.2 What is the normal What is the normal global distributionglobal distribution pattern of pattern of temperature?temperature?

Part APart A



Quit

What is the relationship between location and

annual mean temperature of the

following three places?

What is the relationship between location and

annual mean temperature of the

following three places?

What is the major factor affecting air temperature?What is the major factor affecting air temperature? Monthly mean temperatures

What makes the air temperature vary among latitudes and at different

times of a year?

What makes the air temperature vary among latitudes and at different

times of a year?

Insolation.



Quit

What is insolation?

In order to have a better understanding of the issue of global warming, we have to know more about insolation.

Space

The atmosphere

Earth’s surfaceEarth’s surface

Insolation

Solar radiation

The sun is constantly releasing energy in all directions. This energy is known as solar radiation.

Solar radiation that is received in the atmosphere or on the earth’s surface is known as insolation.



Quit

What is insolation?Is insolation evenly distributed on the earth?

The distribution of insolation on the earth’s surface is ( even / uneven ).

Average annual insolation over the earth’s surface

In general, insolation received ( declines / increases ) with increasing latitude.

+

-

-

More insolation

Less insolation



Quit

What is insolation?Is insolation evenly distributed on the earth?

Which areas receive the highest value of insolation?

The areas around _______ N and S receive the highest value of insolation.

Average annual insolation over the earth’s surface

Why does insolation vary with latitudes?

Why does insolation vary with latitudes?



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What is insolation?What factors affect insolation received on the earth’s surface?

Factors affecting insolation received on the earth’s surface

Angle of the sun

Duration of daylight

The atmosphere

LatitudeTime of a

daySeason



Quit

In Part B, we will discuss the relationship between insolation

and air temperature.



Quit



Quit

1 Angle of the sunThe angle of the sun refers to the angle at which sunlight strikes the earth’s surface.When the sun is directly overhead, or when the angle of the sun is 90°, it is known as the overhead sun.

Overhead sun

How does the angle of the sun affect the

intensity of insolation?

How does the angle of the sun affect the

intensity of insolation?

Area A Area B

Angle of the sun

Area to warm up

Intensity of insolation

90° / Right angle < 90° / Acute angle

Smaller

High / More intense

Larger

Low / Less intense



Quit

1 Angle of the sunA Latitude

In low-latitude regions:

The angle of sun is ( smaller / larger ).

The insolation concentrates on a ( smaller / larger ) area.

Therefore, the insolation is ( weaker / stronger ).

(Credit: NASA)



Quit

1 Angle of the sunA Latitude

In high-latitude regions:

The angle of sun is ( smaller / larger ).

The insolation concentrates on a ( smaller / larger ) area.

Therefore, the insolation is ( weaker / stronger ).

(Credit: NASA)



Quit

1 Angle of the sunB Time of a day

The amount of insolation received in a mid-latitude site in the Northern Hemisphere around the spring equinox

The angle of sun ( decreases /

increases / reaches maximum )

The sun at noon is called the midday sun





How is the amount of insolation received in this

site different in winter?

How is the amount of insolation received in this

site different in winter?

The amount of insolation received

will be lower in winter.



Quit

What is the relationship between the seasons in Hong Kong

and insolation?

What is the relationship between the seasons in Hong Kong

and insolation?

1 Angle of the sunC Season

Please click above for animation

N

In summer solstice, the overhead sun is located at _______ which is close to Hong Kong. It is the time that Hong Kong receives the ( least / largest ) amount of insolation.

In autumnal equinox, the overhead sun is located at the _________. Hong Kong receives less insolation in autumn than in summer.

Equator

S

In winter solstice, the overhead sun is located at _________. It is the time that Hong Kong receives the ( least / largest ) amount of insolation.

In spring equinox, the overhead sun is located at the Equator. Hong Kong receives ( more / less ) insolation in spring than in winter.



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2 Duration of daylightThe longer the duration of daylight, the ( less / more ) insolation received.The duration of daylight in equatorial regions is almost 12 hours daily throughout a year.

Equator

Equator

Is the case in polar areas different?

Is the case in polar areas different?



Quit

In polar regions, daylight can last for 24

hours in summer.

While in winter, there is no

sunlight at all.

2 Duration of daylight

When does the North Pole receive the largest amount of insolation?When does the North Pole receive the largest amount of insolation?



Quit

How does the atmosphere affect

the amount of solar radiation reaching

the earth’s surface?

How does the atmosphere affect

the amount of solar radiation reaching

the earth’s surface?

The dust particles, gas molecules and clouds in the atmosphere are able to reflect, absorb or scatter solar radiation.

3 The atmosphereOnly about 58 units of solar radiation reaches the earth’s surface.



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3 The atmosphere

Maximum insolation received



Why does the maximum insolation received occur at around N

and S but not at the Equator?

Why does the maximum insolation received occur at around N

and S but not at the Equator?



Quit

Space

The atmosphere

Dense cloud cover

Insolation is reflected by

clouds

Less cloud cover

Less cloud cover

3 The atmosphere

The amount of cloud cover in the equatorial regions is high. Much of the solar radiation is

reflected by clouds. This may reduce the amount of insolation reaching the earth’s surface.

The climate is drier and there is less cloud cover at around N and S. The earth’s surface receives more insolation, so the amount of insolation is greatest here.

0° NS

© Oxford University Press 2009 Part 7 Global warming─Are humans responsible? Quit 7.2What is the normal global distribution global distribution pattern.

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