The Earth’s Atmosphere

The Earth’s The Earth’s AtmosphereAtmosphere

Overview of the Earth’s atmosphereOverview of the Earth’s atmosphere Vertical structure of the Vertical structure of the

atmosphereatmosphere

Early AtmosphereEarly Atmosphere

The evolution of life and the atmosphere are The evolution of life and the atmosphere are closely linked – 4 billion years ago ancestors of closely linked – 4 billion years ago ancestors of green plants produced the oxygen green plants produced the oxygen (photosynthesis) and cycles the carbon ((photosynthesis) and cycles the carbon (e.g. e.g. limestone)limestone)-These early organisms began to change the Earth’s atmosphere -These early organisms began to change the Earth’s atmosphere slowly, but drastically!slowly, but drastically!

Oxidized modern atmosphere (NOxidized modern atmosphere (N22, O, O22, CO, CO22, , etc.etc.))

Overview of the Overview of the Earth’s Earth’s

AtmosphereAtmosphere• The atmosphere, when scaled to the size of an

apple, is no thicker than the skin on an apple.• Atmosphere: 1.The envelope of gases surrounding the earth or

another planet: Nitrogen, oxygen, helium, neon, argon, water vapor, and other substances.2. This is the mixture that we call “air.”

Composition of the Composition of the AtmosphereAtmosphere

The “dry atmosphere”: The “dry atmosphere”: 78% N78% N22, 21% O, 21% O22, , 1% Ar1% Ar

• NN22 is primordial – it’s been part of the is primordial – it’s been part of the atmosphere as long as there’s been an atmosphere as long as there’s been an atmosphereatmosphere

• OO22 has been rising from none at all has been rising from none at all about 2.2 Gya – comes from about 2.2 Gya – comes from photosynthesisphotosynthesis

Layers of the AtmosphereLayers of the Atmosphere

vertical temperature (T) profilevertical temperature (T) profile tropospheretroposphere stratospherestratosphere mesospheremesosphere thermospherethermosphere

• Temperatures, winds, Temperatures, winds, humidity and pressures high humidity and pressures high above the ground are above the ground are measured twice-daily by measured twice-daily by radiosonde.radiosonde.

TroposphereTroposphere

• This layer contains the weather• Tropopause-

StratosphereStratosphere

This layer sits on This layer sits on top of the top of the tropospheretroposphere

It’s elevation ranges It’s elevation ranges from 10 km to from 10 km to around 25 kmaround 25 km

This layer contains This layer contains the ozone layer, the ozone layer, which protects us which protects us from harmful from harmful sunlightsunlight

MesosphereMesosphere

ThermosphereThermosphere

This is the highest layer of the This is the highest layer of the atmosphereatmosphere

It’s height ranges from 100 to 400 It’s height ranges from 100 to 400 kmkm

This is where most small meteorites This is where most small meteorites burn up and is also the location in burn up and is also the location in the atmosphere that the northern the atmosphere that the northern lights occur (aurora borealis)lights occur (aurora borealis)

Lapse RateLapse Rate

The rate at which air temperature The rate at which air temperature decreases with height.decreases with height.

The standard (average) lapse rate in The standard (average) lapse rate in the lower atmosphere is about 6.5°C the lower atmosphere is about 6.5°C per 1 km or 3.6°F per 1000 ft.per 1 km or 3.6°F per 1000 ft.

Temperature InversionTemperature Inversion

An increase in air temperature with An increase in air temperature with height often called simply an height often called simply an inversion.inversion.

LayersLayers

Troposphere – Temp decrease w/ heightMost of our weather occurs in this layerVaries in height around the globe, but Averages about 11 km in height.

LayersLayers

Stratosphere-Temperature inversion in stratosphereOzone plays a major part in heating the air at this altitude

LayersLayers

Mesosphere-Middle atmosphere – Air thin, pressure low,Need oxygen to live in this region. Air quite Cold -90°C (-130°F) near the top of mesosphere

LayersLayers

Thermosphere“Hot layer” – oxygen molecules absorb energy from solar Rays warming the air. Very few atoms and molecules in this Region.

TemperatureTemperature in atmospheric in atmospheric layerslayers

The troposphere is warmed primarily by The troposphere is warmed primarily by the Earth’s surface; temperature the Earth’s surface; temperature decreasesdecreases as altitude increases in this as altitude increases in this layer.layer.

Temperatures Temperatures increaseincrease as altitude as altitude increases in the stratosphere, increases in the stratosphere, particularly in the upper portion – ozoneparticularly in the upper portion – ozone

Temperatures Temperatures decreasedecrease with altitude in with altitude in the mesospherethe mesosphere

Thermosphere is the first to receive Thermosphere is the first to receive Sun’s rays, so they are very Sun’s rays, so they are very hothot

OverviewOverview