Earth's Atmosphere

Earth's Atmosphere

• Describe the Properties of the atmosphere

• Identify the four main layers of the atmosphere

• Explain Heat Transfer and interaction of air masses in the troposphere

​Lesson Objectives

Properties of the Atmosphere

• Atmosphere: The thin layer of gases that surrounds the Earth

  • Is extremely Thin

• We live at the bottom of the atmosphere

• Functions

  • Provides Oxygen

  • Protects from harmful sun rays

  • Transports Water

  • Burns up Meteors

  • Controls Climate

Composition of the Atmosphere

• 78% of the air is made up of Nitrogen gas (N₂)

  • Few organisms can use Nitrogen in the atmospheric form, so it needs to undergo nitrogen fixation by bacteria

• 21% is Oxygen (O₂)

  • Needed for breathing and combustion

  • Oxygen was not in the atmosphere originally but built up from photosynthesis

• The remaining 1% is Trace Gases and Water Vapor

Relative Humidity

• Air does not always hold the same amount of water

• Relative Humidity: the ratio of water vapor the air contains to the maximum amount it could have at that temperature

  • Example: In Pheonix, the average relative humidity is 31%, so the air only holds 31% of the air it could hold

Condensation

• In general warm air can hold more water vapor than cooler air

• On Land

  • When warm air cools, it condenses into liquid dew

  • If the air temperature is below freezing it condenses into frost

• When vapor condenses on particles in the air clouds are formed

  • Particles include salt crystals, smoke, and dust

Air Temperature and Pressure

• Air Temperature varies at different places and at different times

  • Some areas are more exposed to the sun's rays than others

• Air Pressure: The Force exerted by air on the area around it

  • Every molecule of air has weight that pushes on the area around it

  • Barometer: an instrument that measures air pressure.

    • Two types: Mercury & Aneroid

Mercury Barometer

• Mercury Barometer: air pressure pushes a column of mercury upwards in a tube

  • More pressure makes the mercury rise higher

  • Measured in inches

Aneroid Barometer

• Aneroid Barometer: a metal chamber whose walls bend inward when air pressure is high

  • Walls bulge out when the pressure is low

  • As the walls bend, a dial moves to indicate a change in air pressure

    • measured in millibars

Altitude and Air Pressure

• In general, the lower altitude the higher the air pressure

  • More pressure pushes down from higher up in the atmosphere

Multiple Choice

The layer of gases that surrounds the Earth is called the:

• atmosphere

• biosphere

• hydrosphere

• lithosphere

Multiple Choice

Two gases that make up 99% of Earth's atmosphere

• carbon dioxide & oxygen
• nitrogen & carbon dioxide
• nitrogen & oxygen
• nitrogen & water vapor

Multiple Choice

How much oxygen do we have in earth’s atmosphere?

• 78%

• 20.9%

• 33%

• 40.2%

Layers of the Atmosphere

• We divide the atmosphere into four main layers

  • Layers are based on changes in temperature

The Troposphere

• The lowest layer of the atmosphere that is right above the ground

  • Thinner than other layers

  • Ranges between 7-18 kilometers in height

    • thinnest at the poles and thickest at the equator

• Contains oxygen and clouds

  • The movement of air in the troposphere creates weather

• Makes up 75% of the mass of the atmosphere

• Becomes colder as you go higher up

• The top has a layer that stops it from merging with the layer above

The Stratosphere

• The layer above the troposphere

• extends 11-50 kilometers above sea level

• Gases do not mix with each other, so pollutants tend to remain for a long time

• Gets warmer as you move higher

  • Maximum temperature of -3 degrees Celsius

• Contains a natural layer of Ozone (O₃)

  • Traps Ultra violet rays and keeps them from reaching the surface

The Mesosphere & Thermosphere

• Mesosphere: The layer above the stratosphere

  • Extends 50-80 Kilometers above sea level

  • Gets colder as you move higher

  • Extremely low air pressure

• Thermosphere: The top layer of the atmosphere

  • begins 80 kilometers above sea level

  • The thinnest layer of the atmosphere

  • Has a very high temperature

Multiple Choice

Which of the following identifies the layers of the atmosphere in correct order, beginning with the lowest layer?

• Stratosphere, Troposphere, Mesosphere, Thermosphere

• Troposphere, Stratosphere, Thermosphere, Mesosphere

• Thermosphere, Mesosphere, Stratosphere, Troposphere

• Troposphere, Stratosphere, Mesosphere, Thermosphere

Multiple Choice

This is the only layer of the atmosphere with active weather.

• Troposphere
• Mesosphere
• Thermosphere
• Stratosphere

Multiple Choice

Temperature decreases as altitude increases in the Thermosphere.

• True
• False

Multiple Choice

Which layer of the atmosphere absorbs UV light?

• troposphere

• stratospere

• thermosphere

• mesosphere

Multiple Choice

Temperature in the stratosphere warms as altitude increases.

• True
• False

Multiple Choice

What causes the temperature to increase in the stratosphere?

• Nitrogen
• Ozone
• Water Vapor
• carbon dioxide

The Troposphere and Weather

• Weather: the atmospheric conditions over short periods in small areas

• Climate: the pattern of atmospheric conditions in large regions over longer periods of time

• Energy from the sun drives the air movement that creates weather

  • Heat always moves from a warmer substance to a colder substance

  • Moves in three different ways

Radiation

• Radiation: The transfer of energy through space

  • how heat from the sun travels through the atmosphere

  • Involves no direct contact

  • Dark objects absorb more radiation than light objects

    • Light objects reflect radiation away

Conduction

• Conduction: heat transfer through objects that directly touch each other

  • occurs when molecules collide

  • In the troposphere is caused by molecules in the air in direct contact with the surface of the Earth

Convection

• Convection: the transfer of heat by the movement of currents within a fluid

  • As objects get warmer, they become less dense and rise to a point where they begin to cool and sink back down

• Convection Current: the sinking and rising of warm air

  • Cause winds and move heat through the troposphere

Air Masses and Fronts

• Air Mass: a large body of air

  • Properties within a front tend to be similar

    • Temperature, Pressure, and Humidity

• Front: The boundary between air masses that differ in temperature and moisture

Warm Fronts

• Warm Front: a boundary along which a mass of warmer, moist air pushes against a mass of cold dry air

  • The warm air rises and cools

  • Cold air holds less moisture than Warm air, so the vapor in the air condenses and forms clouds with light rain fall

Cold Fronts

• Cold Front: a boundary along which a mass of colder, dry air pushes against a mass of warm, moist air

  • The colder air pushes the warm air up so it cools to form clouds

  • The sudden change causes rapid condensation and heavy precipitation if there are large amounts of vapor in the air

  • Create sudden weather changes including heavy storms

Multiple Choice

Thermal energy ALWAYS moves from _____ to _____.

• Solid to Liquid

• Cold to Hot

• Hot to Cold

• Solid to Gas

Multiple Choice

Heat from the sun travels to Earth by _____.

• conduction
• convection
• insulation
• radiation

Multiple Choice

A boundary along which a mass of warm, moist air replaces a mass of cool dry air is called a(n)...

• Air Front

• Cold Front

• Warm Front

• Convection Front

Multiple Choice

The Energy for Weather on Earth comes from....

• the Earth's core
• volcanoes
• geothermal vents
• the Sun

Multiple Choice

What is the percentage of nitrogen in Earth's atmosphere?

• 1%
• 21%
• 78%
• 90%