The AtmosphereThe Atmosphere

The AtmosphereThe Atmosphere

The atmosphere is the envelope The atmosphere is the envelope of gases that surround our planetof gases that surround our planet

It is a very thin layer compared to It is a very thin layer compared to the radius of the Earththe radius of the Earth

State of the AtmosphereState of the Atmosphere

We discuss and study the atmosphere in We discuss and study the atmosphere in terms of the following variables:terms of the following variables:

PressurePressure TemperatureTemperature WindWind HumidityHumidity Cloud coverCloud cover Precipitation type and amountPrecipitation type and amount Visibility (distance one can see horizontally)Visibility (distance one can see horizontally)

Weather vs. ClimateWeather vs. Climate

• Weather is the state of the Weather is the state of the atmosphere at a particular time and atmosphere at a particular time and a particular place.a particular place.

• Climate is the long-term state of the Climate is the long-term state of the atmosphere at a particular location.atmosphere at a particular location.

Atmospheric CompositionAtmospheric Composition

Dry air (neglecting water vapor) is Dry air (neglecting water vapor) is composed of the following gases:composed of the following gases:

Nitrogen (NNitrogen (N22)) = 78%= 78%

Oxygen (OOxygen (O22)) = 21%= 21%

Argon (Ar)Argon (Ar) = 1%= 1%

Trace GasesTrace Gases

Dust, bacteria, and other particulatesDust, bacteria, and other particulates

Atmospheric CompositionAtmospheric Composition

Trace GasesTrace Gases• Gases that are only found by examining Gases that are only found by examining

a million or billion air moleculesa million or billion air molecules• Examples include:Examples include:

Carbon Dioxide (COCarbon Dioxide (CO22) = 340 ppmv) = 340 ppmv Neon (Ne) = 18 ppmvNeon (Ne) = 18 ppmv Helium (He) = 5 ppmvHelium (He) = 5 ppmv Methane (CHMethane (CH44) = 2 ppmv) = 2 ppmv Hydrogen (HHydrogen (H22) = 0.5 ppmv) = 0.5 ppmv

Composition of AirComposition of Air There are many There are many

different types of different types of gasses in the gasses in the atmosphereatmosphere

They include They include nitrogen, oxygen, nitrogen, oxygen, argon, carbon argon, carbon dioxide and other dioxide and other noble gassesnoble gasses

The gas that is most The gas that is most abundant is nitrogenabundant is nitrogen

Vertical Layers of the AtmosphereVertical Layers of the Atmosphere

The Earth’s atmosphere has 4 distinct The Earth’s atmosphere has 4 distinct layers that are identified by the way layers that are identified by the way temperature changes with height. temperature changes with height. These layers are:These layers are:

- Troposphere- Troposphere

- Stratosphere- Stratosphere

- Mesosphere- Mesosphere

- Thermosphere- Thermosphere

Vertical Layers of the Vertical Layers of the Atmosphere (continued)Atmosphere (continued)

Layers of the atmosphere are determined Layers of the atmosphere are determined based on how temperature changes based on how temperature changes

TroposphereTroposphere

This is the layer closest to the Earth’s This is the layer closest to the Earth’s surfacesurface

Almost all the weather phenomenon Almost all the weather phenomenon we know of occurs in this layer.we know of occurs in this layer.

The depth of the troposphere varies The depth of the troposphere varies by the season (deeper in summer)by the season (deeper in summer)

Temperature on average decreases Temperature on average decreases with height.with height.

StratosphereStratosphere

The next layer above the troposphereThe next layer above the troposphere The boundary between the stratosphere The boundary between the stratosphere

and troposphere is called the tropopause.and troposphere is called the tropopause. The ozone layer is found hereThe ozone layer is found here Some clouds can form here near the polesSome clouds can form here near the poles Temperature increases with heightTemperature increases with height Very little mixing occurs between the Very little mixing occurs between the

troposphere and stratosphere.troposphere and stratosphere.

MesosphereMesosphere The mesosphere is the next layer above the The mesosphere is the next layer above the

stratosphere.stratosphere. Clouds are rare in the mesosphere.Clouds are rare in the mesosphere. Temperature decreases with height in the Temperature decreases with height in the

mesospheremesosphere

ThermosphereThermosphere

The thermosphere rests above the The thermosphere rests above the mesosphere, and no clouds exist.mesosphere, and no clouds exist.

Temperature increases with height in Temperature increases with height in the thermosphere.the thermosphere.

The highest temperatures for the The highest temperatures for the atmosphere occur in the atmosphere occur in the thermosphere, but it doesn’t feel hot thermosphere, but it doesn’t feel hot because the atmosphere is so thin up because the atmosphere is so thin up there.there.

Thermosphere (continued)Thermosphere (continued)

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)

Atmospheric DensityAtmospheric Density

Density and pressure in the Density and pressure in the atmosphere decrease exponentially atmosphere decrease exponentially with heightwith height

Approximately 75% of the total Approximately 75% of the total atmosphere is in the troposphereatmosphere is in the troposphere

Approximately 99% of the Approximately 99% of the atmosphere is the troposphere and atmosphere is the troposphere and stratospherestratosphere