Humidity 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.

http://www.srh.noaa.gov/crp/?n=education-heattransfer Air Masses

A body of air that has the same temperature and humidity throughout. What is an air mass?

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 How do air masses form?

Location, Location, Location… 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). Location, Location, Location…

Where do air masses form? Air masses tend to form in areas with little wind. Remember, they sit over an area for a long period of time without moving. Where do air masses form?

Air masses that form over water are called maritime. Air masses that form over land are called continental. Labeling Air Masses

Classification of Air Masses mT – maritime tropical cT – continental tropical mP – maritime polar cP – continental polar cA – continental arctic Classification of Air Masses

http://www.srh.noaa.gov/crp/?n=education-airmasses Location of Air Masses

Characteristics of Air Masses mT – warm, moist air cT – warm, dry air mP – cold, moist air cP – cold, dry air cA – super cold, dry air Characteristics of Air Masses

How do air masses move? Convection! http://commons.wikimedia.org/wiki/File:Convection.gif How do air masses move?

Convection Warm air rises, and cold air moves in to replace it. A circulation pattern is formed. Causes air and water currents to form Convection

How does convection work? Density! Warm air rises. Cool air sinks. How does convection work?

How do different air masses form? Reflection Question

http://www.srh.noaa.gov/crp/?n=education-hurricanes Hurricanes 15

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 Katrina http://ngs.woc.noaa.gov/katrina/ 22

Reflective Question How do oceans play a role in the development of weather systems including hurricanes? 23

Winds http://openclipart.org/detail/167014/kite-by-pomprint 24

The movement of air in a horizontal direction What is wind?

The uneven heating of the Earth causes differences in air pressure. http://www.srh.noaa.gov/crp/?n=education-basicproperties What causes wind? 26

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?

Convection As warm air at the equator rises, cooler air from the poles will move in and replace it. http://commons.wikimedia.org/wiki/File:Convection.gif 29

Global Convection Currents 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 http://www.srh.noaa.gov/jetstream/global/circ.htm 30

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 http://cimss.ssec.wisc.edu/sage/meteorology/lesson2/concepts.html 31

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.

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

Prevailing Winds Named for the direction from which they blow: Polar Easterlies – High latitudes blow east to west toward the equator Westerlies – Mid latitudes blow west to east toward the poles Easterlies (Trade Winds) – Low latitudes blow east to west toward the Equator

Prevailing Winds

Prevailing Winds Pressure belts form in between the wind belts.

MoreDirect Sun Hot 0 o Equator 30 o S 60 o S 90 o S 30 o N 60 o N

Global Wind Belts The winds from the poles blow toward the equator. The winds from the equator blow toward the poles. http://cimss.ssec.wisc.edu/sage/meteorology/lesson2/concepts.html http://oceanmotion.org/guides/cf_2/cf_student_2.htm 39

If wind is moving north and south, … …then why is it defined as the horizontal movement of air? Does the Earth stand still?

The Coriolis Effect 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. At this point, stop and allow students to investigate. See the Handout: Coriolis Effect and Teacher Resource: Coriolis Effect KEY. 42

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

Equilibrium 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?

How are winds produced? Reflection Question

Ocean Currents http://oceanservice.noaa.gov/education/yos/resource/JetStream/ocean/circulation.htm 46

Ocean Currents Warm currents flow away from the equator. Cold currents flow toward the equator. Ocean Currents

Factors Influencing Currents Sun Wind Coriolis Gravity

Sun 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.

Convection Cycle http://commons.wikimedia.org/wiki/File:Convection_cycle.png 50

Wind 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 http://oceanmotion.org/guides/cf_2/cf_student_2.htm 52

Gravity 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.

The Coriolis Effect 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 55

Surface Currents 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

http://upload. wikimedia http://upload.wikimedia.org/wikipedia/commons/c/cc/Ocean_surface_currents.jpg Surface Currents 57

Gyres Vertical columns or mounds of water at the surface and flow around them Produce enormous circular currents Five major locations: North Pacific - clockwise South Pacific - counterclockwise Indian Ocean - counterclockwise South Atlantic - counterclockwise North Atlantic - clockwise

Oceanic Gyres http://commons.wikimedia.org/wiki/File:Oceanic_gyres.png 59

Gulf Stream 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

Upwelling 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 http://oceanmotion.org/html/background/upwelling-and-downwelling.htm 62

The Great Ocean Conveyor: Helps maintain Earth’s Balance http://oceanservice.noaa.gov/education/yos/resource/JetStream/ocean/circulation.htm The Great Ocean Conveyor: Helps maintain Earth’s Balance 63

Deep Water Currents 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.

How are ocean currents produced? Reflective Question

El Nino 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 Winter http://www.srh.noaa.gov/crp/?n=education-elninoandlanina 68

El Nino Summer http://www.srh.noaa.gov/crp/?n=education-elninoandlanina 69

La Nina Abnormally low surface ocean temperatures off the coast of South America Causes unusual weather patterns across the globe

Ocean’s Effect on Climate 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 from? The warm currents?

Predictable Patterns How do these currents affect the climate of the coastline? http://oceanservice.noaa.gov/education/yos/resource/JetStream/ocean/circulation.htm 72

Reflection Questions How do our oceans impact climate?