Chapter The Atmosphere: Structure and Temperature 17 The... · Composition of the Atmosphere 17.1 Atmosphere Characteristics Weather is constantly changing, and it refers to the state

Chapter The Atmosphere: Structureand Temperature

Geologists have uncovered evidence of when Earth was first able to support oxygen-rich atmosphere similar to what we experience today and more so, take for granted.

Research shows that it was 500 million years ago that a reversal took place, whereinfrom containing carbon dioxide, the atmosphere began containing oxygen, suitable forbreathing. It is precisely this reversal that caused a revolutionary change. It was fromthis day that Earth began capable of supporting living organisms.

For the last ten years, researchers at the Ohio State University had been gathering andFor the last ten years, researchers at the Ohio State University had been gathering andputting together evidence of when the Earth might have first been able to contain anoxygen-rich atmosphere. This was basically done by measuring the amounts ofchemical from different rock cores around the world to chain a series of events.

The chain of events was described this way : Tectonic activity led to increasedweathering, which basically pulled carbon dioxide from the air, thereby cooling theclimate. As the oceans cooled down, the plankton prospered - and in turn created moreoxygen through photosynthesis.

Since the reversal of that greenhouse effect, oxygen levels have been stable for the last50 million years, having started fluctuating over the last 500 million.

The most crucial element of life support in space is a breathable atmosphere. A humanin space, whether in a craft, station, or suit, must have air. As such, we have to thanknature’s way of allowing us to come into this air and for sustaining our existence.

Image Credit: CESCG

Composition of the Atmosphere

17.1 Atmosphere Characteristics

Weather is constantly changing,and it refers to the state of theatmosphere at any given time andatmosphere at any given time andplace. Climate, however, is basedon observations of weather thathave been collected over manyyears. Climate helps describe aplace or region.



Major Components

• Air is a mixture of different gases• Air is a mixture of different gasesand particles, each with its ownphysical properties.

Volume of Clean, Dry Air



Variable Components

• Water vapor is the source of all• Water vapor is the source of allclouds and precipitation. Likecarbon dioxide, water vaporabsorbs heat given off by Earth. Italso absorbs some solar energy.


Variable Components

• Ozone is a form of oxygen thatcombines three oxygen atoms intoeach molecule (O3).


each molecule (O3).

• If ozone did not filter most UVradiation and all of the sun’s UVrays reached the surface of Earth,our planet would be uninhabitablefor many living organisms.



Human Influence

• Emissions from transportation• Emissions from transportationvehicles account for nearly half theprimary pollutants by weight.

Primary Pollutants

Height and Structure of the Atmosphere


The atmosphere rapidly thins asyou travel away from Earth untilthere are too few gas molecules tothere are too few gas molecules todetect.

• Atmospheric pressure is simplythe weight of the air above.

Pressure Changes

AtmosphericPressure vs. Altitude


Temperature Changes

• The atmosphere can be dividedvertically into four layers based ontemperature.


temperature.

• The troposphere is the bottomlayer of the atmosphere wheretemperature decreases with anincrease in altitude.


Temperature Changes

• The stratosphere is the layer of theatmosphere where temperature


atmosphere where temperatureremains constant to a height ofabout 20 kilometers. It then beginsa gradual increase until thestratopause.

Snowy Mountaintops Contrast withWarmer Snow-Free Lowlands



Temperature Changes

• The mesosphere is the layer ofthe atmosphere immediatelythe atmosphere immediatelyabove the stratosphere and ischaracterized by decreasingtemperatures with height.



Temperature Changes• The thermosphere is the region of

the atmosphere immediately abovethe atmosphere immediately abovethe mesosphere and ischaracterized by increasingtemperatures due to the absorptionof very short-wave solar energy byoxygen.

Thermal Structure of the Atmosphere

Earth-Sun Relationships


Earth’s Motions• Earth has two principal motions—

rotation and revolution.rotation and revolution.

Earth’s Orientation• Seasonal changes occur because

Earth’s position relative to the suncontinually changes as it travelsalong its orbit.

Tilt of Earth’s Axis


Solstices and Equinoxes• The summer solstice is the

solstice that occurs on June 21 or22 in the Northern Hemisphere and


22 in the Northern Hemisphere andis the “official” first day of summer.

• The winter solstice is the solsticethat occurs on December 21 or 22in the Northern Hemisphere and isthe “official” first day of winter.



Solstices and Equinoxes

• The autumnal equinox is theequinox that occurs on Septemberequinox that occurs on September22 or 23 in the NorthernHemisphere.

• The spring equinox is the equinoxthat occurs on March 21 or 22 inthe Northern Hemisphere.

Length of Daylight


The length of daylight comparedto the length of darkness also isdetermined by Earth’s position inorbit.

Solstices and Equinoxes

Energy Transfer as Heat

17.2 Heating the Atmosphere

Heat is the energy transferredfrom one object to anotherbecause of a difference in thebecause of a difference in theobjects’ temperature.

Temperature is a measure of theaverage kinetic energy of theindividual atoms or molecules in asubstance.


Three mechanisms of energytransfer as heat are conduction,convection, and radiation.

Conduction


• Conduction is the transfer of heatthrough matter by molecularactivity.

Conduction


• Convection is the transfer of heat

Convection


• Convection is the transfer of heatby mass movement or circulationwithin a substance.




Electromagnetic Waves

• The sun emits light and heat aswell as the ultraviolet rays that

• The sun emits light and heat aswell as the ultraviolet rays thatcause a suntan. These forms ofenergy are only part of a large arrayof energy emitted by the sun, calledthe electromagnetic spectrum.

Electromagnetic Spectrum

Visible Light Consistsof an Array of Colors


Radiation• Radiation is the transfer of energy

(heat) through space byelectromagnetic waves that travel


electromagnetic waves that travelout in all directions.

• Unlike conduction and convection,which need material to travelthrough, radiant energy can travelthrough the vacuum of space.


Radiation

• All objects, at any temperature,emit radiant energy.


• Hotter objects radiate more totalenergy per unit area than colderobjects do.


Radiation cont.

• The hottest radiating bodiesproduce the shortest wavelengthsof maximum radiation.


of maximum radiation.

• Objects that are good absorbers ofradiation are good emitters as well.


When radiation strikes an object,there usually are three different

results.1. Some energy is absorbed by the

object.

What Happens to Solar Radiation?

object.2. Substances such as water and air

are transparent to certainwavelengths of radiation.

3. Some radiation may bounce offthe object without being absorbedor transmitted.

Solar Radiation



Reflection

• Reflection occurs when light• Reflection occurs when lightbounces off an object. Reflectionradiation has the same intensity asincident radiation.



Scattering

• Scattering produces a larger• Scattering produces a largernumber of weaker rays that travelin different directions.


Absorption

• About 50 percent of the solarenergy that strikes the top of the


energy that strikes the top of theatmosphere reaches Earth’ssurface and is absorbed.


Absorption

• The greenhouse effect is theheating of Earth’s surface and


heating of Earth’s surface andatmosphere from solar radiationbeing absorbed and emitted by theatmosphere, mainly by water vaporand carbon dioxide.

Why Temperatures Vary

17.3 Temperature Controls

Factors other than latitude thatexert a strong influence onexert a strong influence ontemperature include heating ofland and water, altitude,geographic position, cloud cover,and ocean currents.



Land and Water

• Land heats more rapidly and to• Land heats more rapidly and tohigher temperatures than water.Land also cools more rapidly andto lower temperatures than water.

Mean Monthly Temperaturesfor Vancouver and Winnipeg


Geographic Position

• The geographic setting can greatlyinfluence temperaturesexperienced at a specific location.experienced at a specific location.

Mean Monthly Temperatures forEureka and New York City

Mean Monthly Temperaturesfor Seattle and Spokane



Altitude

• The altitude can greatly influencetemperatures experienced at aspecific location.

Mean Monthly Temperatures forGuayaquil and Quito



Cloud Cover and Albedo

• Albedo is the fraction of totalradiation that is reflected by any

• Albedo is the fraction of totalradiation that is reflected by anysurface.

• Many clouds have a high albedoand therefore reflect back to spacea significant portion of the sunlightthat strikes them.

Clouds Reflect and Absorb Radiation

World Distribution of Temperature


Isotherms are lines on a weathermap that connect points where thetemperature is the same.temperature is the same.

• Isotherms generally trend east andwest and show a decrease intemperatures from the tropicstoward the poles.

The End

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Chapter The Atmosphere: Structure and Temperature 17 The... · Composition of the Atmosphere 17.1 Atmosphere Characteristics Weather is constantly changing, and it refers to the state