The Atmosphere

The Atmosphere

• Earth’s atmosphere serves a vital role in our survival, it– Blocks harmful uv rays– Maintains our warm temperature– Supplies the oxygen we need to breathe

• As we learned in out last unit, our activities have comprised the atmosphere’s role in protecting us

The Atmosphere

• Earth’s atmosphere is comprised of 78% Nitrogen, 21% Oxygen, and 1% of other gases that surround the planet.

• Water vapor makes up part of the “other” 1%, but can fluctuate between 0 and 4%. The higher the water vapor, the more Nitrogen and Oxygen decrease.

Atmospheric Concentrations

The Atmosphere

• The further we go out from Earth’s surface, the thinner the atmosphere is, until it reaches space

• The atmosphere is broken into four main layers (we’ve reviewed the first 2 already) followed by the exosphere – which is basically outer space– Troposphere– Stratosphere– Mesosphere– Thermosphere ( contains the ionosphere)

The Atmosphere

• Troposphere– First layer above Earth’s surface (reaches from 7-

20km above the ground)– Half of Earth’s atmosphere exists in the

troposphere– Weather occurs in the troposphere– We also previously learned that pollution in this

layer causes smog and bad ozone production

The Atmosphere

• Troposphere (cont)– This layer is heated from the ground (as the sun

warms the Earth, the ground radiates, or heats) the troposphere. So, the further upward we go into the troposphere, the colder it gets.

– The air also gets thinner the higher up you go (this is what it get’s harder for some people to breathe in higher elevations, such as mountains

– Most the water vapor and dust particles in the exist in this layer, so most clouds occur here.

Kinds of Clouds

• 3 basic kinds…1. Cirrus – light and feathery. Made of ice

crystals at 10,000m2. Cumulus – big and puffy. Made from rising

currents of warm air that build to great heights

3. Stratus – sheet like. Form layer upon layer at low altitudes.

Fog

• A cloud that forms near the ground is fog.• Fog forms from condensation.• You see this when cool air moves in over warm

air usually in…– Valleys– Rivers– Lakes– Other low areas

Cumulonimbus Clouds

• Cumulus clouds that are associated with thunderstorms.

• Updrafts can raise high to the top of the troposphere.– The top flattened and looks like an anvil.– An anvil is a good indication a thunderstorm is

coming.

Let’s Name that Cloud….

Let’s Name that Cloud….

Let’s Name that Cloud….

Let’s Name that Cloud….

Let’s Name that Cloud….

The Atmosphere

• Stratosphere– 2nd layer from Earth’s surface (between 16-50 km above

the Earth)– Very stable, allowing for jet aircraft to fly here to avoid the

turbulence they experience in the troposphere– The ozone layer exists here, absorbing radiation from the

sun. This process heats the stratosphere. – The further up you go into the stratosphere, the hotter it

gets (opposite of the troposphere)– Very little water vapor here, so almost no clouds (polar

stratospheric clouds are the exception - PSCs)

PCSs

• Found at altitudes of 15 to 25 km (9.3 to 15.5 miles

• They appear to help create “Ozone Holes” by encouraging certain chemical reactions that destroy ozone.

PCSs

The Atmosphere

• Mesosphere– Third layer up from the Earth. Goes from 50-85km high– The higher you go up in the Mesosphere, the colder it

gets (like the troposphere)– We don’t know much about this layer, because satellites

orbit above it, and weather balloons and jet aircraft can’t fly high enough to reach it

– We know that most meteors from space burn up in this layer (so we don’t get hit by them often)

– One kind of cloud forms here – Noctilucent Clouds

Noctilucent Clouds

• A special type of clouds, called "noctilucent clouds“ (PMCs), sometimes forms in the mesosphere near the North and South Poles.

• They form much higher than any other type of cloud

• There are also odd types of lightning in the mesosphere. These types of lightning, called "sprites" and "ELVES"

PMCs

The Atmosphere

• Thermosphere– 4th layer from the Earth (goes from 90km – between

500-1000km high)– Temperatures sharply increase the higher you go in

the thermosphere and is influenced by solar activity (from 200-2000 degrees C or 360-3632 degrees F)

– Even though it’s considered part of Earth’s atmosphere, the air density is so low that it’s considered mostly the same as outerspace.

– Aurora (the Southern and Northern Lights) occur here

Atmospheric Temperatures

The Atmosphere

• Thermosphere– The lower portion of the thermosphere is called

the Ionosphere– The ionosphere is a layer of electronically charged

particles– When solar energy collides with these particles, it

creates ions and free electrons, which interfere with radio waves sent from Earth, bouncing them back. This is how AM radio transmissions can bounce from one side of the Earth to the other.

Radio waves and the Ionosphere

The Atmosphere

• Exosphere– Above the Thermosphere, where outer space

starts. For most part, not considered Earth’s atmosphere

– The is the layer where air molecules escape into space

– Space shuttles orbit the Earth here– There are so few to no air molecules, so there is

no wind. So the wings of the shuttles(which are used in the lower layers) are useless here