Topic 6- Atmospheric systems and societies
6.1 Introduction to the atmosphere
THE ATMOSPHERE IS A DYNAMIC SYSTEM
The atmosphere is a dynamic system (with inputs, outputs, flows and storages)
that has undergone changes throughout geological tim.
The atmosphere is a mixture of solids, liquids and gases that are held to the Earth
by gravitational force.
Atmospheric composition
Up to a height of around 80km the atmosphere is fairly similar, consisting of
nitrogen (78%), oxygen (21%), argon (0.9%) and a variety of other trace gases
such as carbon dioxide, helium and ozone. In addition it contains water vapor and
solids (aerosols), such as dust, ash and soot.
There is no outer limit to the atmosphere, but most ‘weather’ occurs in the
lowest 15km- the troposphere.
Human impact on the atmosphere
Human activities impact atmospheric composition through altering inputs and
outputs of the system. Changes in the concentrations of atmospheric gases- such
as ozone, carbon dioxide and water vapor- have significant effects on ecosystems.
Atmospheric reactions
Most reactions connected to living systems occur in the inner layers of the
atmosphere, which are the troposphere (around 0-15km above sea level) and the
stratosphere (around 10-50km above sea level).
Clouds
Most clouds form in the troposphere and play an important role in the albedo
effect of the planet. Albedo varies from 0.08 for moist, dark soils to about 0.9 for
fresh snow. Clouds have an average albedo of about 0.5, so greatly restrict the
amount of short wave radiation reaching the ground below them. Low, thick
clouds, such as stratus clouds, reflect more short- wave radiation than thin, wispy,
cirrus clouds.
KEY DEFINITION
Albedo- A measure of the reflecting power of a surface in relation to the amount of short-
wave radiation received.
THE GREENHOUSE EFFECT
The greenhouse effect of the atmosphere is a natural and necessary phenomenon maintaining
suitable temperatures for living systems.
In the troposphere, temperatures fall with height
Certain gases are concentrated at certain heights
Ozone occurs in the stratosphere, most around 25-30km
The greenhouse effect is a natural process and is necessary for life on Earth. The accelerated
or enhanced effect refers to the changes in the greenhouse effect that are commonly referred
to as global warming.
QUICK CHECK QUESTIONS
-Identify the two main gases in the troposphere
-In which part of the atmosphere does most weather occur?
-Outline the role of the greenhouse effect in regulating temperature on Earth
Discuss the role of the albedo from clouds in regulating global average temperature
6.1 Introduction to the atmosphere
THE ATMOSPHERE IS A DYNAMIC SYSTEM
The atmosphere is a dynamic system (with inputs, outputs, flows and storages)
that has undergone changes throughout geological tim.
The atmosphere is a mixture of solids, liquids and gases that are held to the Earth
by gravitational force.
Atmospheric composition
Up to a height of around 80km the atmosphere is fairly similar, consisting of
nitrogen (78%), oxygen (21%), argon (0.9%) and a variety of other trace gases
such as carbon dioxide, helium and ozone. In addition it contains water vapor and
solids (aerosols), such as dust, ash and soot.
There is no outer limit to the atmosphere, but most ‘weather’ occurs in the
lowest 15km- the troposphere.
Human impact on the atmosphere
Human activities impact atmospheric composition through altering inputs and
outputs of the system. Changes in the concentrations of atmospheric gases- such
as ozone, carbon dioxide and water vapor- have significant effects on ecosystems.
Atmospheric reactions
Most reactions connected to living systems occur in the inner layers of the
atmosphere, which are the troposphere (around 0-15km above sea level) and the
stratosphere (around 10-50km above sea level).
Clouds
Most clouds form in the troposphere and play an important role in the albedo
effect of the planet. Albedo varies from 0.08 for moist, dark soils to about 0.9 for
fresh snow. Clouds have an average albedo of about 0.5, so greatly restrict the
amount of short wave radiation reaching the ground below them. Low, thick
clouds, such as stratus clouds, reflect more short- wave radiation than thin, wispy,
cirrus clouds.
KEY DEFINITION
Albedo- A measure of the reflecting power of a surface in relation to the amount of short-
wave radiation received.
THE GREENHOUSE EFFECT
The greenhouse effect of the atmosphere is a natural and necessary phenomenon maintaining
suitable temperatures for living systems.
In the troposphere, temperatures fall with height
Certain gases are concentrated at certain heights
Ozone occurs in the stratosphere, most around 25-30km
The greenhouse effect is a natural process and is necessary for life on Earth. The accelerated
or enhanced effect refers to the changes in the greenhouse effect that are commonly referred
to as global warming.
QUICK CHECK QUESTIONS
-Identify the two main gases in the troposphere
-In which part of the atmosphere does most weather occur?
-Outline the role of the greenhouse effect in regulating temperature on Earth
Discuss the role of the albedo from clouds in regulating global average temperature
