3A body of air that has the same temperature and humidity throughout. What is an air mass?
4If 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.TemperatureHumidityHow do air masses form?
5Location, 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…
6Where 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?
7Air masses that form over water are called maritime. Air masses that form over land are called continental.Labeling Air Masses
8Classification of Air Masses mT – maritime tropicalcT – continental tropicalmP – maritime polarcP – continental polarcA – continental arcticClassification of Air Masses
16What 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.
17What conditions must exist for a hurricane to form? Low to medium winds blowing in the same direction5–30 degrees north of the equator in the oceanOcean surface temperature of greater than 80 F that extends down to about 150 feet deep (50 m)Lower atmosphere must be moist
18How 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.
19How 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.
20Where 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.
21Why don’t hurricanes form in higher latitudes? The temperature of the oceans is not warm enough.The distance is too far from the equator.
25The movement of air in a horizontal direction What is wind?
26The uneven heating of the Earth causes differences in air pressure. What causes wind?26
27The 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?
28As 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?
29ConvectionAs warm air at the equator rises, cooler air from the poles will move in and replace it.29
30Global 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 Currents30
31Where 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 Belts31
33Jet StreamForms high in the upper Troposphere between two air masses of different temperaturesHigher temperature difference = faster speedDue 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.
34http://www.pbs.org/wgbh/nova/vanished/jetstr_five. html Jet Stream Animation
35Prevailing Winds Named for the direction from which they blow: Polar Easterlies – High latitudes blow east to west toward the equatorWesterlies – Mid latitudes blow west to east toward the polesEasterlies (Trade Winds) – Low latitudes blow east to west toward the Equator
37Prevailing WindsPressure belts form in between the wind belts.
38MoreDirect Sun Hot 0 o Equator 30 o S 60 o S 90 o S 30 o N 60 o N
39Global Wind Belts The winds from the poles blow toward the equator. The winds from the equator blow toward the poles.39
40If wind is moving north and south, … …then why is it defined as the horizontal movement of air? Does the Earth stand still?
41The Coriolis EffectAs 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.
42The Coriolis EffectIn 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
43Weather patterns and systems move in a circular motion due to the bending of the winds caused by the Earth’s rotation.The Coriolis Effect
44Equilibrium 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?
51WindJust 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.
53GravityAs 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.
54The Coriolis EffectCauses water to move to the right in the Northern HemisphereCauses water to move to the left in the Southern Hemisphere
58GyresVertical columns or mounds of water at the surface and flow around themProduce enormous circular currentsFive major locations:North Pacific - clockwiseSouth Pacific - counterclockwiseIndian Ocean - counterclockwiseSouth Atlantic - counterclockwiseNorth Atlantic - clockwise
63The Great Ocean Conveyor: Helps maintain Earth’s Balance The Great Ocean Conveyor: Helps maintain Earth’s Balance63
64Deep 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.
65How are ocean currents produced? Reflective Question
66El NinoAbnormally high surface ocean temperatures off the coast of South AmericaCauses unusual weather patterns acrossthe globe
67El NinoStarts because the easterly trade winds weaken and allow the warm waters in the Western Pacific to move east toward South AmericaThis changes where the convection current occurs.Causing rain where it usually doesn't occur and drought where it usually rains
70La NinaAbnormally low surface ocean temperatures off the coast of South AmericaCauses unusual weather patterns acrossthe globe
71Ocean’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?
72Predictable Patterns How do these currents affect the climate of the coastline? 72
73Reflection QuestionsHow do our oceans impact climate?