Presentation on theme: "Unit 2: Climate Winds and Climate"— Presentation transcript:
1 Unit 2: Climate Winds and Climate World GeographyUnit 2: ClimateWinds and Climate
2 The Circulation of AirThe circulation of air follows a general pattern:The equator receives the most solar energy, therefore is heated the most.Air above the equator heats rapidly and expands, becoming less dense.This air risesAs the air rises, it cools and is pushed towards the poles, it is pushed by air still rising from the equator.This cooling air becomes more dense, and begins to fall back to earth.As it falls back to earth it forces colder air toward the equator where the cycle continues.2.3.5 Explain how wind systems andtemperature are related. (k)
3 The Circulation of Air This process is known as a convection cell Convection Cell: A current in the atmosphere in which warmer, lighter air moves upward and is replaced by colder, heavier air.The movement of the air depends on the density of the airWarm air is moist, less dense, and lighter.These are low pressure areas.Cool air is dry, dense, and heavy.These are high pressure areasWhen areas of low and high pressure are next to each other the air flows from high to low.This flow is known as Wind.
4 The Circulation of AirAir moves vertically in convection cells to equalize temperature.Air moves horizontally by wind to equalize pressure.
6 Prevailing WindPrevailing Wind: The most frequently occurring wind direction at a given location.The circulation of air from the equator to the poles and back is complicated by two things:The spinning of the planetThe uneven distribution of water and land on the planet
7 Prevailing WindsThe movement of air from the equator to the poles is broken into three convection cells in each hemisphere:Trade winds: 0⁰-23.5 ⁰ (equator to tropics)Westerlies : 23.5 ⁰ ⁰(tropics to arctic circle)Polar easterlies: 66.5 ⁰-to pole (arctic circle to pole)These latitudes do change due to two factors:Variations in Earths Surface: Ocean and ContinentEarth’s relative position to the sun: They will move with the seasons
10 Coriolis EffectThe apparent deflection of moving objects (wind, ocean currents, missiles) from traveling in a straight path, in proportion to the speed of Earth’s rotation at different latitudes.Deflection is:To the right in the Northern HemisphereTo the left in the Southern Hemisphere.Maximum effect at the polesMinimum effect at the equator
12 The Major Pressure Belts Wind systems are driven by pressure belts that can be found in the different areas of prevailing wind.These are areas of high and low pressure.High pressure:Downward movingPushing outward-Spins clockwise in the north and counter clockwise in the southLow pressure:Rising airAir that pulls inwardSpins counter clockwise in the north and clockwise in the south
14 Pressure Belts The Pressure systems are Equatorial Low Pressure Trough Subtropical High-PressureSub Polar Low PressurePolar High
15 Pressure Belts Equatorial Low Pressure Trough: Broken band of clouds that straddle the equatorConstant high sun altitude and consistent day length make enormous amounts of energy availableLots of light, wet, ascending air.As air rises it cools, and water in the air condenses.Home of the intertropical convergence zone,Shifts between the tropics depending on season.This area is dominated by the TRADE WINDS!!!
16 Pressure Belts Subtropical High- Pressure Cells: Hot, dry, desert air Cloudless skiesAir forced downward by compression from low pressure cells, is heated.THIS AREA IS ASSOCIATED WITH THE WESTERLIES
17 Pressure Belts Subpolar Low-Pressure Cells: Cool, moist air. These cells DOMINATE in the winter, weakening, or disappearing in the summer.THESE CELLS FORM BETWEEN THE WESTERLIES AND POLAR EASTERLIES
18 Pressure Belts Polar High-Pressure Cells: Frigid, dry deserts These are weak systems.Near the poles there is little energy from the sun to power up weather systemsTHIS PRESSURE BELT IS RESPONSIBLE FOR FORMING THE POLAR EASTERLIES
20 Land and Sea Breezes Land-Sea breezes occur on most coastlines. However they have different characteristics.
21 Sea Breeze During the day the land is heated by the sun. This causes air to warm and rise forming a low pressure system over the land.As the air rises it is pushed over the sea where it cools and descends (high pressure)This high pressure is drawn into the land creating a breeze that comes off of the water.
23 Land Breeze At night water is often warmer than land This causes the air above the water to rise, forming a low over the water.As the air rises it is driven in over the land, cools and descends.The cool air is drawn back out to sea by the low pressure.This creates a breeze that comes from the land.
25 Wind Systems and Temperature As seasons change the temperature difference will cause pressure belts and prevailing winds to shift.The equatorial low follows the sun between the tropics with the seasons.This causes the other systems to shift to compensate.
26 Points to Remember: WARM AIR RISES FORMING LOW PRESSURE AS AIR RISES IT COOLSCOOL AIR DESCENDS FORMING HIGH PRESSURECOOL AIR CANNOT HOLD MOISTURE AS WELLCONDENSATION HAPPENS WHEN AIR CANNOT HOLD ITS MOISTURE
27 Precipitation: Orographic Orographic Precipitation: (relief rainfall) this forms when moisture-laden air masses are forced to rise over high ground. The air is cooled, the water vapour condenses, and precipitation occursWindward side: The side of the mountain that the prevailing wind blows against. Where the air rises, and precipitation occursLeeward side: The side of the mountain in which the air begins to descend again. This area is dry as the air mass has lost its moisture.Rainshadow: Area where little rain falls due to the loss of moisture within the air mass due to its rising over a landform.
31 Precipitation: Convectional Convection rainfall happens when the land is heated by the sun. The air above this land is then heated and rises. Moisture from the Earth’s surface evaporates and rises with the warm air. As the air rises it cools so this moisture condenses and falls as rain. The continuous cycle of rising warm air and falling cool air creates a convection current in the atmosphere.This type of rainfall is generally not accompanied by wind.
33 The Relationship Between Precipitation and Location Where does each type of rainfall occur?Orographic: Where westerly winds meet coastal mountains after crossing bodies of water.Frontal: where low pressure meets high pressure.Convectional: Mostly over the tropics, however sometimes in the summer.