Learning ObjectivesDescribe the composition and layers of the

Earth’s atmosphere.Explain three mechanisms of heat transfer in

Earth’s atmosphere.Explain the greenhouse effect.

The AtmosphereAtmosphere – the mixture of gases that surrounds

the EarthThe envelope of gases that surrounds the planet.The atmosphere is made up of a mixture of atoms

and molecules of different kinds.Contains mostly nitrogen, oxygen, carbon dioxideThese gases are constantly added and removed

Animals and humans breath in and outPlants produce foodVolcanoes eruptCars

Composition of the AtmosphereNitrogen = 78%•Volcano eruptions•Dead plants and animals decay

Oxygen = 21%•Plants

Other Gases = 1%•Argon•Carbon Dioxide•Methane•Water Vapor

Composition of the AtmosphereAtmosphere also contains atmospheric dustMainly soilSaltAsh from firesVolcanic ashParticulate matter from combustionSkinHairBits of clothingPollenBacteria and virusesaerosols

Air PressureEarth’s atmosphere is pulled toward Earth’s

surface by gravityThis makes the atmosphere denser near Earth’s

surfaceAlmost the entire mass of Earth’s atmospheric

gases is located with 30 km of the surface.The air is less dense at higher altitudes. This

makes breathing more difficult.A barometer is how you measure air pressure by

mercury, which contains vacuum mercury. The aneroid barometer which contains vacuum chamber, lever, spindle and pointer. (video)

Mercury BarometerA mercury barometer is an accurate and relatively simple way to measure changes in atmospheric pressure. At sea level, the weight of the atmosphere forces mercury 760 mm (29.9 in) up a calibrated glass tube. Higher elevations yield lower readings because the atmosphere is less dense there, and the thinner air exerts less pressure on the mercury.

Aneroid BarometerIn an aneroid barometer, a partially evacuated metal drum expands or contracts in response to changes in air pressure. A series of levers and springs translates the up and down movement of the drum top into the circular motion of the pointers along the aneroid barometer's face.

Mercurial Barometer

Aneroid Barometer

Layers of the AtmosphereThe atmosphere is divided into four layers

based on temperature changes that occur at different distances above the Earth’s surface.TroposphereStratosphereMesosphereThermosphere

Without our atmosphere, there would be no life on Earth. A relatively thin envelope, the atmosphere consists of layers of gases that support life and provide protection from

harmful radiation.

The TroposphereClosest to Earth’s surface18 km above Earth’s surfaceAlmost all weather occurs hereDensest atmospheric layerTemperature decreases as altitude increases

The StratosphereFrom 18 km to about 50 kmTemperature rises as altitude increases in

stratosphereOzone in the stratosphere absorbs the sun’s

ultraviolet (UV) energy and warms the airOzone, O3, is made up of three oxygen atomsAlmost all ozone in the atmosphere is located

in the ozone layer of the stratosphereOzone reduces the amount of UV radiation

that reaches Earth.

The MesosphereFrom 50 km to 80 km above Earth’s surfaceThe coldest layer of the atmosphereTemperatures as low as -93°C.

The ThermosphereThe layer farthest from the Earth’s surfaceNitrogen and oxygen absorb solar radiation

The absorption causes atoms to be electrically charged.

These ions radiate energy as light.Temperatures above 2,000°CIf we could travel here, it would not feel hot to

usAir particles that strike one another transfer heatThe air in the thermosphere is so thin that air

particles rarely collide so they rarely transfer heat.

LAYER OF THE ATMOSPHERE BASED ON COMPOSITION OF GASES

OZONOSPHERE - In this layer ozone concentrations are about 2 to 8 parts per million, which is much higher than in the lower atmosphere but still very small compared to the main components of the atmosphere.Ozone layer is located in the lower portion of

the stratosphere from about 15–35 km (9.3–22 mi; 49,000–110,000 ft), though the thickness varies seasonally and geographically. About 90% of the ozone in our atmosphere is contained in the stratosphere.

LAYER OF THE ATMOSPHERE BASED ON COMPOSITION OF GASES

IONOSPHERE - the part of the atmosphere that is ionized by solar radiation, stretches from 50 to 1,000 km (31 to 620 mi; 160,000 to 3,300,000 ft) and typically overlaps both the exosphere and the thermosphere. - It forms the inner edge of the magnetosphere. - It has practical importance because it influences, for example, radio propagation on the Earth.- It is responsible for auroras.

LAYER OF THE ATMOSPHERE BASED ON DISTRIBUTION OF GASES

HOMOSPHERE HETEROSPHERE

HOMOSPHERE the chemical composition of the

atmosphere does not depend on molecular weight because the gases are mixed by turbulence.

includes the troposphere, stratosphere, and mesosphere.

Above the turbopause at about 100 km (62 mi; 330,000 ft) (essentially corresponding to the mesopause), the composition varies with altitude.

HETEROSPHEREallows the gases to stratify by molecular

weight, with the heavier ones such as oxygen and nitrogen present only near the bottom of the heterosphere.

The upper part of the heterosphere is composed almost completely of hydrogen, the lightest element.

This is because the distance that particles can move without colliding with one another is large compared with the size of motions that cause mixing.

VIDEOSBeginningThe divisions of the earth atmosphereReveal Earth's Atmosphere

Three Types of Heat TransferRadiation – Transfer of energy across space

Conduction – Flow of heat from a warmer object to a colder object when placed in direct contact

Convection – The transfer of heat by air currents

Conduction, Convection, Radiation

Heating of the AtmosphereSolar energy reaches Earth as

electromagnetic radiation.Electromagnetic radiation includes visible

light, infrared radiation, and ultraviolet light.Almost half of the solar energy that enters

the atmosphere passes through and reaches Earth’s surface

The rest is absorbed in the atmosphere by clouds, gases and dust or it is reflected by the Earth’s surface.

Movement of Energy in the Atmosphere

Weather is caused by air that is constantly moving upward, downward or sideways

Currents of less dense air, warmed by the Earth’s surface, rise into the atmosphere.

Currents of denser, cold air sink toward the ground.

As currents of air rise into the atmosphere they cool off

Eventually, the air current becomes more dense than the air around it and sinks.

Convection current – Continual process of warm air rising and cool air sinking. A circular motion.

The Greenhouse EffectA greenhouse is a

building where plants are grown.

Solar radiation enters the building and heats up the inside faster than heat can escape.

Greenhouse GasesGreenhouse Gases – The gases in our

atmosphere that trap and radiate heatNone of the greenhouse gases have a high

concentration in the Earth’s atmosphereThe most abundant greenhouse gases are

Water vapor (varies because of natural processes)

Carbon dioxide (varies because of industry)Methane (varies because of industry)Nitrous oxide

The Greenhouse EffectThe gases in Earth’s atmosphere act like the glass in a

greenhouse.Sunlight penetrates the Earth’s atmosphere and heats

the surface of the Earth.The Earth’s surface radiates heat back to the

atmosphere where only some of the heat escapes into space.

The rest of the heat is absorbed by the greenhouse gases, which warms the air.

Heat is then radiated back toward the surface of the Earth.

Without the greenhouse effect Earth would be too cold to live.