*The relative measure of the amount of water vapor in the air

*Psychrometer

*Water vapor affects the density of the air.

*Cold air is heavier than warm air.

* A body of air that has the same temperature and humidity throughout.

*If a large body of air sits over an area of land or water for a long period of time, it will take on the characteristics of the land or water beneath it.

*Temperature

*Humidity

*Air masses over the equator will have high temperatures.

*Air masses over polar regions will have low temperatures.

*Air masses over water (maritime) will have high humidity (moisture content).

*Air masses over land (continental) will have low humidity (moisture content).

*Air masses tend to form in areas with little wind.

*Remember, they sit over an area for a long period of time without moving.

*Air masses that form over water are called maritimemaritime.

*Air masses that form over land are called continentalcontinental.

*mTmT – maritime tropical

*cTcT – continental tropical

*mPmP – maritime polar

*cPcP – continental polar

*cAcA – continental arctic

*mTmT – warm, moist air

*cTcT – warm, dry air

*mPmP – cold, moist air

*cP cP – cold, dry air

*cAcA – super cold, dry air

Convection!Convection!

*Warm air rises, and cold air moves in to replace it.

*A circulation pattern is formed.

*Causes air and water currents to form

Density!Density!

*Warm air rises.

*Cool air sinks.

How do different air masses form?

*HurricanesHurricanes

*What is a hurricane?

*Hurricanes are tropical cyclones.

*They form in the southern Atlantic Ocean, Caribbean, Gulf of Mexico, and eastern Pacific Ocean.

*Their winds spiral outward in a counterclockwise, circulation pattern.

*What conditions must exist for a hurricane to

form?

* Low to medium winds blowing in the same direction

*5–30 degrees north of the equator in the ocean

*Ocean surface temperature of greater than 80 F that extends down to about 150 feet deep (50 m)

* Lower atmosphere must be moist

*How do hurricanes form?

* The air mass above the tropical waters takes on the temperature and humidity of the water beneath it.

* Incoming winds force the air upward.

* The warm, moist air rises, forming water vapor and clouds.

* Above the storm, the winds flow outward.

* Outside winds blow inward, and the cycle repeats.

*How do hurricanes move?

*Hurricanes turn to the right, away from the equator, because of the Coriolis Effect caused by Earth’s rotation.

*You will learn about this phenomenon later in the lesson.

*Where does the energy for a hurricane originate?

*The Sun heats the oceans.

*Warm air rises, and as it cools, it releases energy, fueling the hurricane.

*Why don’t hurricanes form in higher latitudes?

*The temperature of the oceans is not warm enough.

*The distance is too far from the equator.

*Hurricane KatrinaHurricane Katrina

*Reflective QuestionReflective Question

How do oceans play a role in the development of weather systems including hurricanes?

*WindsWinds

*The movement of air in a horizontal direction

*What is wind?

*The uneven heating of the Earth causes differences in air pressure.

*What causes wind?

*The Sun’s energy is more concentrated at the Equator and spread out more over the poles.

*Air over the equator is warm and less dense and has lower pressure.

*Air over the poles is cold and denser and has higher pressure.

*Why does this happen?

*As warm air at the equator rises, cooler air from the poles will move in and replace it.

*Air pressure moves in a pattern from high to low.

*Why does this happen?

*As warm air at the equator rises, cooler air from the poles will move in and replace it.

*Convection

*The density changes caused by temperature changes create convection cells.

*These cause circular patterns of air that circulate over the whole planet.

*Global Convection

Currents

*Where the convections cells meet, prevailing winds and jet streams form.

* They blow from one direction over a certain area of the Earth’s surface.

*Global Wind Belts

*Jet Stream

*Jet Stream*Forms high in the upper Troposphere between

two air masses of different temperatures*Higher temperature difference = faster speed*Due to the Coriolis Effect, it flows around air

masses.*Polar Jet:* It dips southward when frigid polar air masses

move south.* It tends to stay north in the summer months.

*Jet Stream Animation

http://www.pbs.org/wgbh/nova/vanished/jetstr_five.html

*Named for the direction from which they blow:* Polar Easterlies Polar Easterlies – High latitudes blow east to west

toward the equator

*WesterliesWesterlies – Mid latitudes blow west to east toward the poles

* Easterlies (Trade Winds) Easterlies (Trade Winds) – Low latitudes blow east to west toward the Equator

*Prevailing Winds

*Prevailing Winds

*Pressure belts form in between the wind belts.

*Prevailing Winds

0 o Equator 30 o S 60 o S 90 o S30 o N60 o N90 o N

MoreDirect Sun Hot

*The winds from the poles blow toward the equator.

*The winds from the equator blow toward the poles.

*Global Wind Belts

……then why is it defined as the then why is it defined as the horizontal movement of air?horizontal movement of air?

Does the Earth stand still?Does the Earth stand still?

*If wind is moving north

and south, …

*As the Earth rotates counterclockwise, the winds bend and curve around the Earth.

*Gustave-Gaspard Coriolis, an engineer and mathematician, described this effect as an inertial force in 1835.

*The Coriolis Effect

*In the Northern Hemisphere, winds bend to the right of their direction of travel.

*In the Southern Hemisphere, winds bend to the left of their direction of travel.

*Let’s try a little investigation to see how this works.

*The Coriolis Effect

*Weather patterns and systems move in a circular motion due to the bending of the winds caused by the Earth’s rotation.

*The Coriolis Effect

*Our Earth is always seeking balance.

*In an effort to find balance, there is a continuous cycle of patterns.

*What is the driving force behind the changes that create these patterns?

*Equilibrium

How are winds How are winds produced?produced?*Reflection

Question

Ocean CurrentOcean Currentss

Warm currents flow away from the equator.

Cold currents flow toward the equator.

*Ocean Currents

*Sun

*Wind

*Coriolis

*Gravity

*Factors Influencing

Currents

*Energy from the Sun heats the water.

*Warm water is less dense that cold water.

*Warm water rises, and cold water sinks.

*As warm water rises, cold water moves it to replace it.

*Sun

*Convection Cycle

*Just as wind moves from high pressure to low pressure areas, so does the water.

*Winds blow across the surface of the water, causing friction.

*The water piles up because the surface currents flow slower than the winds.

*Wind

*Wind

*As water piles up and flows from high pressure to low pressure, gravity will pull down on the water.

*This forms vertical columns or mounds of water.

*The Coriolis Effect causes the water to curve.

*Gravity

*Causes water to move to the right in the Northern Hemisphere

*Causes water to move to the left in the Southern Hemisphere

*The Coriolis Effect

*The Coriolis Effect

*Make up 10% of oceans’ water

*Up to maximum depth of 400 m

*Surface ocean currents are caused by the surface wind patterns.

*Surface Currents

*Surface Currents

*Gyres

*Oceanic Gyres

*A strong surface current

*Begins at the tip of Florida

*Flows up the eastern coastline of the U.S.

*Crosses the Atlantic Ocean

*Causes warmer climate in NW Europe

*Gulf Stream

*Surface waters blow to the right of the wind.

*As less dense, surface water moves off shore, cold, deep, denser waters come to the surface to replace them.

*Upwelling

*Upwelling

*The Great Ocean Conveyor:

Helps maintain Earth’s Balance

*Make up about 90% of oceans’ water

*Differences in density cause them to move.

*Differences in density are related to temperature and salinity.

*At high latitudes, they sink deep into the ocean basins.

*Temperatures are so cold, they cause the density to increase.

*Deep Water Currents

*How are ocean currents How are ocean currents produced?produced?

*Reflective Question

Abnormally high surface ocean temperatures off the coast of South America

Causes unusual weather patterns across

the globe

*El Nino

*Starts because the easterly trade winds weaken and allow the warm waters in the Western Pacific to move east toward South America

*This changes where the convection current occurs.*Causing rain where it usually doesn't

occur and drought where it usually rains

*El Nino

*El Nino Winter

*El Nino Summer

Abnormally low surface ocean temperatures off the coast of South America

Causes unusual weather patterns across

the globe

*La Nina

*Ocean currents move more slowly than winds.*Oceans hold more heat than the atmosphere

and land.*Cold currents will cause nearby coastlines to be

cooler.*Warm currents will cause nearby coastlines to

be warmer.

Where do the cold currents come Where do the cold currents come from? The warm currents?from? The warm currents?

*Ocean’s Effect on Climate

*Predictable Patterns How do these currents affect the climate of the coastline?

*How do our oceans impact How do our oceans impact climate?climate?

*Reflection Questions