2.1 What is Atmosphere?

​2.1: What is Atmosphere?

Review...

• The early atmosphere contained hydrogen and helium.

• Activities in Earth's interior released other gases, such as carbon dioxide, nitrogen ammonia, and water vapor.

• The first living organisms, such as bacteria and algae, released oxygen into the atmosphere through photosynthesis.

• Now the atmosphere is primarily made up of nitrogen, oxygen, carbon dioxide, and other gases

​Overview

• Identify the chemical composition of the atmosphere

• Describe the physical properties of the atmosphere

• Label the different layers of the atmosphere

• Explain the importance of the ozone layer

​Essential Question: How does the atmosphere influence meteorology?

​Learners can...

Vocabulary

Aerosol: tiny particles or droplets suspended in the air

Air density: the amount of the air molecules in a given space

Biogeochemical cycle: the movement of elements and compounds through living organisms and the environment

Exosphere: the outermost layer of the atmosphere where particles can escape into space

Ionosphere: a part of the atmosphere with ionized particles, located in the mesosphere and thermosphere

Mesosphere: the layer of the atmosphere where most meteors burn up, and it's very cold

Stratosphere: the layer above the troposphere that contains the ozone layer

Temperature inversion: a situation where the temperature increases with altitude instead of decreasing

Thermosphere: a high layer of the atmosphere with high temperatures due to solar radiation

Troposphere: the lowest layer of the atmosphere where most weather occurs

​Something to think about...

• Earth is the only livable planet known to humans, as it can sustain life for a significant period.

• What contributes to this??

Multiple Choice

What distinguishes Earth's atmosphere from those of other planets?

• thickness of the atmosphere

• large percentage of oxygen

• almost all carbon dioxide

​Earth's atmosphere is mostly nitrogen and oxygen!

Multiple Choice

True or False: There is more argon in Earth's atmosphere than nitrogen.

• True

• False

Biogeochemical Cycles in the Atmosphere

The four following cycles ensure constant flow of gases in the atmosphere:

Nitrogen Cycle Water Cycle Oxygen Cycle Carbon Cycle

Physical Properties of the Atmosphere

Air density is the mass of air per unit volume

Relationship between air pressure and density:

• When air pressure increases, the density of air also increases because the gas molecules are more tightly packed together

• When are pressure decreases, the density of air also decreases because the gas molecules are less densely packed

Physical Properties of the Atmosphere

Relationship between air temperature and density:

• When temperature increases, air molecules spread out. This causes the density of air to decrease.

• When temperature decreases, air molecules become densely packed. This causes the density of air to increase.

Physical Properties of the Atmosphere

Relationship between air pressure and temperature:

• When temperature increases, the air becomes warm. Warm air molecules have more energy and move faster, decreasing air pressure.

• When temperature decreases, the air becomes cold. Cold air molecules have less energy and move slower. This increases air pressure.

Physical Properties of the Atmosphere

Relationship between air temperature and density:

Relationship between air pressure and density:

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Relationship between air temperature and air pressure:

​air temperature =

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​air temperature =

​density of air

​air pressure

Physical Properties of the Atmosphere

Relationship between air temperature and density:

Relationship between air pressure and density:

​air pressure =

Relationship between air temperature and air pressure:

​air temperature =

​density of air

​air temperature =

​density of air

​air pressure

​Effects of Air Pressure on Weather and Wind Patterns

• Winds blow from high to low pressure. This movement creates wind patterns across the globe.

• Tighter pressure gradients (closely spaced isobars) result in stronger winds.

• High-pressure systems are usually associated with clear skies and calm weather.

  • Denser air (cooler, drier) tends to sink, contributing to high-pressure systems

  • Sinking air suppresses cloud formation, leading to clearer skies.

• Low-pressure systems often bring clouds, precipitation, and storms.

  • Less-dense air (warmer, moister) tends to rise, forming low-pressure systems.

  • Rising air can lead to cloud formation and precipitation as it cools and condenses.

​Effects of Air Pressure on Weather and Wind Patterns

Multiple Choice

Which of the following effects of high-pressure systems on weather?

• Clear skies

• Thunderstorms

• Clouds and precipitation

​Layers of the Atmosphere

• Exosphere: outermost layer of the atmosphere. Air is very thin here, with low density. Layer does not behave like a gas and particles escape into space

• Thermosphere: located between 53-372 miles above Earth's surface. Also known as upper atmosphere. Solar radiation absorbed here, so temperature is high. Satellites orbit here.

• Ionosphere: NOT a main layer. Part of the atmosphere in the mesosphere and thermosphere where the sun's high-energy radiation ionizes atoms and molecules.

• Mesosphere: Most meteors burn up here. The coldest part of the atmosphere.

• Stratosphere: extends above the troposphere. Contains the ozone layer, which shields Earth from the sun's ultraviolet radiation.

• Troposphere: Lowermost layer of the atmosphere. Extends from Earth's surface to about 5-9 miles high. Most weather happens here.

​Closest

Farthest

Multiple Choice

Which atmospheric layer contains the ozone layer that protects Earth from harmful ultraviolet radiation?

• Troposphere

• Stratosphere

• Mesosphere

​Ozone Layer

• Ozone layer: protects the earth from harmful ultraviolet (UV) radiation by absorbing it before it reaches Earth's surface.

• When UV radiation hits the ozone layer, it causes the oxygen atoms in the ozone molecules to break apart and recombine in different ways.

Multiple Choice

Which statement is correct regarding the composition of Earth's atmosphere?

• Nitrogen and oxygen are abundant, and carbon dioxide is less so.

• Nitrogen and oxygen are in equal amounts in the atmosphere.

• Carbon dioxide makes up most of the atmosphere.

​What did we learn?

​Looking ahead

• categorize Earth's atmosphere and its composition

• explain the role of ozone in meteorology

• identify the effect of air pressure and air density on weather

• label the layers of the atmosphere

• 2.2: Atmosphere and Heat Transfer