EARTH’S ATMOSPHERE

Origins of the Atmosphere

• Boom.• Our atmosphere was created by gases that

vented from erupting volcanoes.• Outgassing• There were three main gasses emitted:1.Water Vapor2.Carbon dioxide3.Nitrogen

• Now the atmosphere is mainly….• If your not sure look at your…..• ESRT1. Nitrogen2. Oxygen• How did this occur?• Plant life began to grow so they converted carbon dioxide to oxygen• Photosynthesis

The Structure of the Atmopshere• The atmosphere is broken into four layers:1. Troposphere2. Stratosphere3. Mesosphere4. Thermosphere• The layers in between the spheres are called:• -pauses

Changes in Air Temperature

• There are two cycles that control our weather:1.The daily weather cycle

2.The season weather cycle

Daily Weather Cycle

• Morning-----------

• 2pm----------------

• 6pm----------------

Seasonal CycleMARCH 21-23 DECEMBER 21-23JUNE 21-23 SEPTEMBER 21-23

What Causes Air Pressure?

• Air Pressure: is the weight of the atmosphere• Proof: Weigh a flat basketball compared to a

basketball filled with air. • At sea-level, the air pressure is nearly 15 lbs

per square inch, or 1013.2 mb.• Millibars: the metric unit of atmospheric

pressure.

STRAW PROOF AIR GOES OUT OF THE STRAW SO PRESSURE DECREASES

Less pressure means that the liquid has nothing holding it back so it moves up the straw

Factors that Affect Atmospheric Pressure

• Altitude• As air rises it expands and there is less gravity

pushing down on it. • More elevation = less air pressure• Indirect relationship

Altitude (elevation)

Air Pressure

Factors (cont)• Temperature:• If air is cooled it comes together and becomes

more dense• More dense air makes it heavier so there is

more air pressure• If air is heated it’s molecules expand and it

becomes less dense• Less dense air makes it lighter so there is less air

pressureAir Pressure

Temperature

Factors (cont)• Humidity• Is the amount of water vapor in the air• Humid air is less dense than dry air• The mass of water is less than the mass of

nitrogen • The atmosphere is made up of primarily which

gas….• Nitrogen• More humidity = less air pressure Air Pressure

Humidity

Measuring Air Pressure• ometer:• Instrument that measures air pressure.• Use to use mercury as a liquid in it to gauge the air

pressure (like a thermometer) so that is how we got the unit inches of mercury.

• In. of Hg• We also use millibars to measure air pressure

Bar

What Causes Wind?

• Wind is the natural movement of air along, parallel to, Earth’s surface.

• These are the result of uneven heating of Earth’s surface.

Warm Air

Lower Pressure

Cool Air

Higher Pressure

More Dense Less Dense

WIND ALWAYS BLOWS FROM AREAS OF HIGHER PRESSURE TO LOWER

PRESSURE!!!!!

•Wind blows fastest where the gradient in air pressure is the greatest.

LAND AND SEA BREEZES

Sea Breeze

A breeze that occurs during the day as there is high pressure (cooler temps) over the water and lower

pressure (warmer temps) over the land.

LAND AND SEA BREEZES

Land Breeze

A breeze that occurs at night when there is high pressure (cooler temps) over the land and lower

pressure (warmer temps) over the water.

How Do Clouds Form?

• Cloud: a collection of billions of tiny droplets or ice crystals (condensation nuclei) suspended in the atmosphere.

• They form when the air is cooled to the dew point temperature.

• This occurs because as air rises into the atmosphere the air is cooled and it expands.

Dry Bulb Temperature line

Dry Bulb Temperature line

Coriolis Effect

• The Earth rotates, and because of this, the winds of the Earth curve.

• Rather than blowing from the Poles to Equator…• In the Northern Hemisphere they curve to the

right of their original path.• In the Southern Hemisphere they curve to the

left of their original path.• This curvature is called the Coriolis Effect.

Coriolis Effect (cont)

• High Pressure Area: • winds move clockwise• Low Pressure Area: • winds move counterclockwise

http://regentsearth.com/Illustrated%20ESRT/Page%2014%20(Wind%20&%20Moisture)/Wind%20&%20Moisture%20index.htm

Dew Point

• When the humidity of the air cools to a certain point, you see water in some form.

• This temperature in which we see water is what we call the dew point.

• The dew point comes mostly when the greatest change in temperature occurs which is…..

• (Think the daily weather cycle)• The morning

How to Find the Dew Point• Using a sling psychrometer you:1.Record the dry bulb reading2.Record the difference between the dry bulb and the

wet bulb (wet bulb will always be less)3.Go to your ESRT and match up those two numbers

to find the Dew Point

Dry Bulb:

22°C

Wet

Bulb:20°CDiff: 2°C

Relative Humidity

• The percentage of humidity in the air is called the relative humidity.

• We use a sling psychrometer to find this as well.

• You also use the same procedure to find the relative humidity.

Pressure Systems

• High Pressure System:• Married to Uncle Cyclone……• Anticyclone• Highs are zones of divergence. • When sinking air at the center causes the

winds to blow outward. • These bring cool and dry air with clear skies

and stable conditions.

High Pressure System

Low Pressure System

• Low Pressure System:• Cyclone• Lows are zones of convergence. • When rising air at the center causes the winds

to blow inward. • These bring warm and moist air with cloudy

skies and unstable conditions.

Low Pressure System

Insolation

• IN coming• SOL ar• Radi ATION• Definition: the sun’s electromagnetic energy

that reaches the Earth.

How Does Heat Energy Travel?

• Heat is a form of energy because it can do work.

• There are three ways that heat can travel1.Convection2.Conduction3.Radiation

Convection

• Convection is the transfer of heat flow in a fluid or a gas.

• Caused by a difference in density.• This creates winds.

Conduction

• Conduction: the form of heat flow in solids that occurs when a hot substance touches a cooler substance.

• Ex. Metal handle of a pot on the stove. Convection

Conduction

Radiation

• Radiation is the flow of energy as electromagnetic waves, such as visible light.

• Heat waves, that you feel but cannot see are also forms of radiation.

• Radiation does not need a medium to travel through.

Electromagnetic Spectrum

REVIEW GAME!!!!

• In your groups, the person with the board will:• Look at the picture on the board• Buzz in when they have written down the correct

transfer of energy• If it is correct your group gets a point• If you buzz in and it is incorrect, you group loses a

point• If there is any calling out, that group loses a point

Conduction

Radiation

Convection

Radiation

Convection

Conduction

Convection

Radiation

All Three

Angle of Insolation

• Angle of Insolation depends on how high the sun is in the sky.

• As the sun rises and sets the a.o.i. changes, ie, the daily weather cycle.

• We measure the a.o.i from the horizon up to the position of the sun.

• Smaller angle=colder temp• Larger angle (90˚)= warmer temps

A.O.I

A.O.I• The a.o.i also works for the seasonal weather cycle. • In the Northern Hemisphere, the lowest noon time

a.o.i is on Dec. 21 and the highest noon time a.o.i is on June 21.

• These are different because Earth is spherical.• The vertical ray is the most direct amount of insolation

(warmer temps), which always hits in the Tropics.• All other latitudes received indirect, or slanted

amounts of insolation (colder temps).

Duration of Insolation• Duration of Insolation is the length of time from sunrise

to sunset. • When Earth has a greater duration of insolation, the

temperatures increase.• Direct Relationship• D.O.I varies greatly with latitude. • Higher the latitude, the more extreme amounts of d.o.i.• Lower the latitude, the more consistent the amounts of

d.o.i.

Energy Absorption

• Colors:• darker=more absorption, less reflection• lighter=less absorption, more reflection

• Surfaces:• shiny=less absorption, more reflection• textured=more absorption, less reflection

Absorption of Insolation by the Atmosphere

• Earth (the solid portion of it) absorbs most of the insolation that falls on it.

• Some that are not absorbed are:• Gamma and X-Rays, which are absorbed by ozone

and other gases in the upper atmosphere• Long-wave radiation, which is absorbed by water

vapor and carbon dioxide in the atmosphere.• SOOOOOO• Visible-light wavelengths easily get through the

atmosphere.

Absorption of Insolation by the Atmosphere (cont)

• Some of the absorbed energy is changed into infrared heat waves that are reradiated from the ground (terrestrial radiation) back into the atmosphere.

Land v. Water Absorption • The difference between the amount of radiation

could be for one or more of the four following reasons:

1.Water has a higher specific heat than land2.Water reflects lower angle insolation better than land3.Water is transparent so insolation goes down further

into it4.Convection currents bring insolation further into the

hydrosphere

Specific Heat

• The amount of energy needed to raise the temperature of a substance by one degree.

Reflection of Insolation

• The Poles are colder than the Equator, even though they both get 12 months of sun and 12 months of darkness, because:

1.Snow at the Poles reflect most of the insolation2.The Sun is lower in the sky at the Poles (a.o.i)3.Sunlight must travel a greater distance through

the atmosphere b/c the Sun is so low in the sky, so it loses energy.

Greenhouse Effect

• Explain it to me.

The Insolation-Temperature Lag

• The Insolation-Temperature Lag is the time delay between the maximum and minimum insolation and the maximum and minimum air temperature.

• Ex. Temp at 6AM compared to Temp at 2PM• Ex. Temp of the ocean in June compare to

Temp of the ocean in Ocobter.

Air Masses• Air Mass: large bodies of air with uniform

temperature.• The movement of these bring us changes in weather. • The leading edge of an air mass is a front.• When a front passes, precipitation often accompanies

the change in temperature, humidity, and atmospheric pressure.

• Then, when the air mass settles in, the weather stabilizes.

How We Categorize Air Mass

• The character of the air mass is determined by the geographic origin of the air that makes it up.

Geographic Origin• There are two general geographic origins for air masses:1. Out of Canada

– This makes the air mass generally cold – Also, because it starts on land the air is dry– This air causes an increase in atmospheric pressure.

2. Out of the Gulf of Mexico – This makes the air mass generally warm– Also, because it starts on over water, the air is moist– This air causes a decrease in atmosphereic pressure

Meet the Air Masses!!• We have developed a system of two-letter codes to identify temperature and humidity characteristics for each air mass.

cP cTmP

mT

c=continentalm= maritimeP= polar

T= tropic A=arctic

cA

Fronts

• Fronts are shown by lines that separate air masses.

• They are often found in low pressure systems because they bring unsettled weather.

• Four types of fronts

Warm Front

• Warm Front: • Is the boundary between a mass of warm air

and the colder mass of air it is pushing out.• Think me trying to push Mr. Roesner. • Brings steady precipitation and low pressure

and may take several days to pass.

Warm Front

Cold Front

• Cold front:• Is the boundary between a mass of cold air

and the warmer air it is pushing out. • Think Mr. Roesner pushing me. • Brings rapid cloud formation, intense

precipitation, high pressure and moves quickly.

Cold Front

Stationary Front• Stationary Front:• The boundary between air masses that are

not moving (stationary).• Think Mr. Roesner and his twin brother

pushing each other. • Winds blow in opposite directions so it does

not move.

Stationary Front

Occluded Front

• Occluded Front:• Forms when warm air is pushed above Earth’s

surface by cooler air that is closing in from both sides.

• Think of a mosh pit. • Rainy, unsettled weather.

Occluded Front

Windward/ Leeward

Adiabatic: as air rises it reduces air pressure and this causes the air to expand and cool