Download Chapter 1 Climatic System and

Shun Lee Catholic Secondary School
Advanced Level – Geography – Climatic System
Chapter 1
Climatic System and Our Atmosphere
1.1
Components of the Climatic System
There are four physical components within the climatic systems:

Atmosphere
the earth’s gaseous envelope
Hydrosphere
liquid water over the surface of the Earth

Lithosphere
land masses: mountain, ocean basins, the surface rocks, sediments and soil

Biosphere
all living organisms

Figure 1.1
Interaction of Different Spheres (After John Wiley & Sons, 1996)
Atmosphere
Hydrosphere
Biosphere
Lithosphere
Chapter 1 Climatic System- P1
Written by Clement Cheng
Chapter 1 Climatic System and Our Atmosphere
1.2
Our Atmosphere
1.2.1
(Vertical) Layering of the Atmosphere
Figure 1.2
The generalized vertical distribution of temperature and pressure up to
about 110 km. Note particularly the tropopause and the zone of maximum ozone
concentration with the warm layer above. Data based on Valley, 1965
Referring to Figure 1.2, how do the climatologists divide the atmosphere
into different layers? The change in temperature.
Chapter 1 Climatic System– P2
Written by Clement Cheng
Shun Lee Catholic Secondary School
Advanced Level – Geography – Climatic System
With reference to Figure 1.2, fill in the following blanks.
Vertical
Position
Change in
temperature with
height
Importance / Special remarks
 The lower portion of the thermosphere is mainly of nitrogen and oxygen.
Thermosphere
(熱成層)
90 km or
above
increase
 Low atmospheric pressure; only 0.001% of its sea level value.
 This layer is affected by cosmic radiation, solar X-rays and ultraviolent
radiation which cause ionization.
Mesosphere(中間層)
55-80 km
decrease
 The pressure of the mesosphere is very low ranging from 1mb at 50 km to 0.01
mb at 90km.
Stratosphere (平流層)
20-50km
increase
 The stratosphere is particularly effective in screening out harmful ultraviolent
rays from the sun and is thus a vital shield for lifeforms at the surface.
 It contains 75% of the total molecular or gaseous mass of the atmosphere and
virtually all the water vapour and aerosols.
 The weather ceiling or the inversion layer is called tropopause.
0-12 km Decrease at a mean  The tropopause limits convection.
Troposphere(對流層)
(ranging rate about 6.5  The height of the tropopause is not constant spatially and temporally. The
from 8 km – C/km
height of the tropopasue at any point is correlated with the temperature, which
16km)
are in turn related to the factors of latitude, season and daily change in the
surface pressure. There are marked variations in the altitude of the
tropopause with latitude, from about 16km at the equator where there is great
heating and vertical convective turbulence to only 8 km at the poles.
Chapter 1 Climatic System- P3
Written by Clement Cheng
Shun Lee Catholic Secondary School
Advanced Level – Geography – Climatic System
1.3
Spatial Distribution of Gases in the Atmosphere
The earth’s atmosphere consists of a mixture of various gases surrounding the earth to
a height of many kilometres. The air is densest at sea level and thins rapidly upward.
Although almost the entire atmosphere (about 97%) lies within 30% of the earth’s
surface, the upper limit of the atmosphere can be drawn approximately a height of 10,
000 km.
1.4
Internal Components of the Atmosphere
(A)
Gas
Components
Symbol
Per cent by Volume
(Dry air)
Nitrogen
N2
78.08
Oxygen
O2
20.98
Argon
Ar
0.93
Carbon dioxide
CO2
0.035
Neon
Ne
0.0018
Helium
He
0.0005
Methane
CH4
0.0017
Krypton
Kr
0.0011
Hydrogen
H
0.00005
Nitrous oxide
N2O
Trace
Xenon
Xe
0.00009
Carbon monoxide
CO
Trace
Ozone
O3
0.00006
Water vapour
H2O
Variable (0-4)
Table 1.1 Average composition of the dry atmosphere below 25 km
Chorley, 1992)
1. Nitrogen and oxygen
Common Characteristics:

Dominant gas

Remarkably constant in the lowest 16 km

Nitrogen is an importance source of fertilizer.
Oxygen
(a) is the most important gas for life.
(b) is needed for combustion
(c) reacts with solid rock causing chemical weathering or reacts with iron

Chapter 1 Climatic System- P5
Written by Clement Cheng
(Barry and
Chapter 1 Climatic System and Our Atmosphere
2. Ozone

Ozone is usually found in the upper stratosphere

Produced by the high level breakup of oxygen molecules by solar ultraviolet
radiation

Destroyed by reactions involving nitrogen oxides and chlorine (CI) (the latter
generated by CFCs, volcanic eruptions and vegetation burning) in the middle and
upper stratosphere
3. Carbon dioxide

It is released from the interior of the earth and produced by respiration, soil


processes combustion and volcanic activity.
Conversely, it is dissolved in the ocean and consumed by the process of plant
photosynthesis.
Carbon dioxide is of great importance in atmospheric processes because of its
ability to absorb radiant heat. Therefore, carbon dioxide augments the warming
of the lower atmosphere by radiant energy coming from the sun and from the
earth’s surface.
4. Water Vapour

Variable in proportion

Dominant in the lower atmosphere

Water vapour gets into the atmosphere through evaporation from oceans and land
surfaces as well as evaportranspiration from plants

In arid areas, there is little water to be evaporated so the atmosphere is also dry,
containing only about 0.5% to 1.0% of water vapour. In humid areas, this figure
may rise to 3% to 4%.
(B) Solid
1.
Dust

Origin:
(a) They have been swept into the air from dry desert plain, lake beds and beaches or
explosive volcanoes. Strong winds blowing over the ocean lift droplets of spray
into the air. These may dry out, leaving as residues tiny crystals of salt that are
carried high into the air.
(b) Forest and brush fires are another sources of atmospheric dust particles.
(c) Some are due to the combustion of fuel in the industrial processes.
Chapter 1 Climatic System– P6
Written by Clement Cheng
Shun Lee Catholic Secondary School
Advanced Level – Geography – Climatic System
Effects of Occurrence of Dust:
Dust contributes to the occurrence of twilight and the red colours of sunrise and
sunset.
Dust also serve as nuclei or centres around which water vapour condenses to produce
cloud particles.

2. Volcanic dust
3. Salt
It is whipped into the air by wave and wind action on sea water.
The water
evaporates leaving common salt, sodium chloride, behind.
4. Smoke
It is far the most important content of the earth’s atmosphere.
1.5
Importance of the Atmosphere
The atmosphere is important in the following ways:
 Allow plants and animals to survive




Shields us from harmful radiation
Stabilize the differences in temperature between tropical and polar regions
Reduces losses of heat from the earth’s surface
Provides water to sustain life
Chapter 1 Climatic System- P7
Written by Clement Cheng