World Geography 3200 Chapter 4 Weather and Climate.

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  • World Geography 3200Chapter 4Weather and Climate

  • Weather & Climate (p.54)Weather: the day-to-day or short-term atmospheric conditionsVariables would include temperature, precipitation, humidity, cloud cover, wind, air pressureClimate: the weather patterns over a long period of timeVariables would include temperature, moisture, air movement

  • The Earth-Sun Relationship (p.55)The sun provides enough heat to energize Earth and keep it warm.

  • The Earth-Sun RelationshipThe sun exerts a gravitational pull on the Earth, so Earth revolves around the sun.

  • The Earth-Sun RelationshipThe Earth is tilted in its orbit, which partially explains the patterns of day and night and the seasons.Because of the tilt, there are only 2 times a year when the sun shines equally on both hemispheres; March 20-23 and September 20-23. These are called equinoxes.

  • Patterns in TemperatureThe range between daytime and nighttime temperatures results from: The amount of cloud cover in the skyThe earths curvatureAt the equator, sunlight comes directly through the atmosphere and strikes the earth directly, hitting a small area (fig 4.3, E)Away from the equator, sunlight comes through the atmosphere at an angle and strikes the earth indirectly, hitting a larger area (fig. 4.3, F)

  • Wind: The Movement of AirAir Circulation Pattern:The air above the equator heats up rapidly and rises, pushing cooler air towards the north and south poles.The cooler this air gets, the more it sinks. As it sinks, it heats up and forces cooler air back towards the equatorand the pattern repeatsThe movement pattern is called a convection cell, which more evenly distributes heat around the world.Convection Cells

  • Wind: The Movement of AirConvection is driven by air density:Warm, moist air is less dense and it floats=Low pressure areasCold, dry air is dense and it sinks=High pressure areasWind is created when air moves from high pressure areas to low pressure areasQuestions: # 15 & 16, pages 61-62.

  • Wind: The Movement of AirPrevailing WindsThere are 6 convection cells which create a series of high and low pressure belts around the earth between which the wind blows. These wind patterns are constant and predictableTrade WindsWesterliesPolar Easterlies

  • Wind: The Movement of Air

  • Wind: The Movement of AirPrevailing Winds (continued)Two factors change how prevailing winds blow:Variations in the Earths surface (constant).The Earths position relative to the sun (varies by season)

  • Wind: The Movement of AirPrevailing Winds (continued)Two factors complicate the pattern of convection currents:The Earths surfaceThe uneven distribution of land and water over the Earths surfaceTwo factors complicate the pattern of convection currents:The Earths surfaceThe uneven distribution of land and water over the Earths surface

  • Wind: The Movement of AirPrevailing Winds (continued)Each hemisphere is broken up into 3 different convection cells (fig 4.10, p.63):0-23.5 degrees latitude23.5-66.5 degrees latitude66.5-polar latitude

  • Wind: The Movement of AirWind & Precipitation Patterns:Humidity: amount of moisture in the air; it comes from the earths surface and evaporates into the atmosphere.

  • Wind: The Movement of AirWind & Precipitation Patterns (continued)2 Basic Principles about Precipitation:When warm air cools, it cannot hold as much water vapour.Temperature rises as air pressure increases; it lowers as air pressure decreases.*Do questions 22-26, p.64-67*

  • Other Factors Affecting ClimateOcean Currents: permanent or semi-permanent horizontal movement of unusually cold or warm surface water of the oceans, to a depth of about 100m. The primary cause of ocean currents is the global movement of winds.Three main factors influence how and where ocean currents flow

  • Other Factors Affecting ClimateOcean Currents

    1. Coriolis Effect: ocean currents shift left or right depending on the hemisphere theyre in.

  • Other Factors Affecting ClimateOcean Currents

    2. The Size and shape of the body of water in which they develop.Ex. The Gulf Stream is deflected northeast by the shape of the North American coastline.

  • Other Factors Affecting ClimateOcean Currents

    3. Differences in water temperature and salt content (remember the effect this had in, The Day After Tomorrow?).These differences cause convection currents similar to those in the atmosphere.

  • Other Factors Affecting ClimateOcean Currents

  • Other Factors Affecting ClimateOcean CurrentsSection questions: 27-30, pages 68-69

  • Other Factors Affecting ClimateContinentalityWater heats up and cools down more slowly than land. Areas near large bodies of water (Vancouver, Botwood) have a maritime climate; the temperature ranges are small and they have more precipitation.Areas far away from water (Calgary, Buchans) have a continental climate; the temp. ranges are large and they have less precipitation.

  • Other Factors Affecting ClimateContinentality and Wind PatternsBecause the suns heat is retained differently by land and waterWinds blow differently in coastal areas than in continental areas.Winds blow differently in mountainous areas than on the plains.

  • Other Factors Affecting ClimateElevation and Climate=height above sea levelthe higher it is, the colder the climate is.

  • Other Factors Affecting ClimateElevation also affects precipitation:Clouds must rise to pass over mountains. As they do, the water vapour in them condenses and rain/snow falls on the windward side. The leeward side (rain shadow) receives little precipitation.

  • Other Factors Affecting ClimateElevation and ClimateSection Questions: page 71-72, #36b., 37, 38, 39,Chapter review questions: page 72, # 40-41


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