Earth’s atmosphere Study Guide
Earth’s atmosphere protects us from solar radiation
The atmosphere traps energy from the sun to keep us warm
It allows water to exist as a liquid
Importance of the Earth's Atmosphere
The first four layers extend to an altitude of about 600 km.
Earth’s atmosphere contains a layer of gases that helps keep temperatures on Earth within a
range that living organisms can survive.
Earth’s atmosphere helps protect living organisms from the Sun’s harmful rays.
Friction within the atmosphere causes most asteroids to burn up before striking Earth.
Origins of Earth’s atmosphere
Earth’s ancient atmosphere formed from hot gases that escaped from Earth’s hardening
surface.
Earth’s ancient atmosphere consisted of water vapor with a little bit of carbon dioxide.
Water Vapor - water is its gaseous state.
As Earth’s atmosphere cooled, the water vapor condensed into a liquid that fell as rain. Over
thousands of years, the rain formed the Earth’s oceans.
Carbon dioxide from the atmosphere dissolved in rainwater and fell into the oceans.
Organisms that use photosynthesis produced the oxygen in today’s atmosphere.
Composition of the Atmosphere
Nitrogen makes us about 78% of Earth’s atmosphere.
Oxygen makes up about 21% of Earth’s atmosphere.
The amount of atmospheric gases (water vapor, carbon dioxide, ozone) vary.
Volcanoes send ash and liquid into the atmosphere.
Air pressure and Altitude
Gravity pulls gas particles in the atmosphere toward Earth’s surface.
Air pressure is greatest near the Earth’s surface because molecules push downward on the
lowest later of ai
Water Vapor - the main component of Earth’s ancient atmosphere
Oxygen - the gas produced by organisms that use photosynthesis
Ozone - is beneficial higher in the atmosphere but is a pollutant down below
Nitrogen - makes up about 78 percent of today’s atmosphere
Acids - liquids produced by the burning of fossil fuels
Troposphere - where weather phenomena occur, atmospheric layer closest to Earth, the
warmest part of the troposphere is near the earth’s surface
Stratosphere - the atmospheric layer below the mesosphere, contains the ozone layer, sun’s
ultraviolet rays are absorbed more effectively by ozone than by oxygen gas
Ionosphere - reflects AM radio waves, within the mesosphere and thermosphere that contains
ions, auroras occur here
Auroras – display of colored light
Exosphere - atmospheric layer farthest from Earth’s surface, farthest layer from the surface, gas
molecules rarely strike each other
Air pressure – always decreases with altitude
Temperature – sometimes decreases with altitude
Radiation - can transfer heat through empty space
Convection – can only transfer heat in fluid, most responsible for heating in our atmosphere
Conduction – the transfer of hear by touch
Latent Heat – Heat added to an object as it changes from one state of matter to another
Sensible heat – Heat added to an object while it changes its temperature
Stable atmosphere – warm air parcels rise slowly in the atmosphere
Unstable atmosphere – warm air parcels rise more quickly in the atmosphere
Radiation – the transfer of energy by electromagnetic waves
Ultraviolet – shorter wavelengths that visible light, can cause sunburn and skin cancer
Infrared radiation – has longer waves then visible light and is felt as heat
Atmosphere - a thin layer of gases surrounding the earth
Mesosphere, thermosphere – much broader than troposphere and stratosphere, less than 1%
of atmospheric gases can be found here
Coriolis effect – the phenomena that causes the turning of global winds
Prevailing Westerlies – Global winds in the Northern hemisphere that are turned toward the
east, blow across most of North America
Temperature and Altitude
In the troposphere and mesosphere temperatures decrease as altitudes increase.
In the stratosphere, thermosphere, and exosphere, temperature increases as
altitude increases.
Energy Transfer in the Atmosphere
Most of the radiation that the Sun gives off is visible light
Energy from the Sun
As the sun’s energy passes through Earth’s atmosphere, about 20% is absorbed by gases and
particles in the atmosphere
Ozone, oxygen, and water vapor absorb ultraviolet light.
Water and carbon dioxide absorb infrared radiation in the troposphere.
Earth’s atmosphere and the surface of earth reflects about 30% of the sun’s radiation that
comes towards Earth.
About 50% of the sun’s radiation that reaches earth’s atmosphere is absorbed by the earth’s
surface.
Radiation Balance
Earth’s temperature remains stable because of the balance between the amount of radiation
coming from the sun and the amount going out from earth.
Land, trees, and the ocean absorb and emit solar radiation, mainly in the form of infrared.
Three main types of radiation that travel from Sun to Earth – infrared, visible, ultraviolet
About 50% of solar radiation makes it to the surface of the Earth and is absorbed by land and
water.
To be seen by our eyes, sunlight must travel through more of the Earth’s atmosphere at sunrise
The Earth absorbs more solar radiation between 35N and 35S latitude than it emits as infrared.
Between 35N and 90N, our Earth emits more radiation than it absorbs.
Three gases that keep out planet warm – Water vapor, carbon dioxide, methane
The Earth absorbs the Sun’s radiation and re-emits it as infrared radiation.
Three main ways heat is transferred from object to object – conduction, convection, radiation
A change in temperature of a fluid can change its density.
Temperature inversions can result in poor air quality at ground level
The sun’s energy strikes the Earth most directly at the equator.
At the poles the sun’s energy is spread out over a larger area.
Global winds are turned to the left in the southern hemisphere and to the right in the northern
hemisphere
Global wind belts are caused by 3 large convection cells in the troposphere.
The wind that blows along the surface is turned because of the Earth’s rotation.
Unequal heating of the Earth’s surface is responsible for wind in the atmosphere.
Warmer (less dense) rises in the atmosphere causing low pressure at the surface
Cooler (more dense) falls in the atmosphere causing high pressure at the surface
Surface winds blow from areas of high pressure to low pressure
Pollution