World Geography 3200World Geography 3200

Chapter 4Chapter 4

Weather and ClimateWeather and Climate

Weather & Climate Weather & Climate (p.54)(p.54)

Weather: the day-to-day or short-term Weather: the day-to-day or short-term atmospheric conditionsatmospheric conditions Variables would include temperature, Variables would include temperature,

precipitation, humidity, cloud cover, wind, air precipitation, humidity, cloud cover, wind, air pressurepressure

Climate: the weather patterns over a long Climate: the weather patterns over a long period of timeperiod of time Variables would include temperature, moisture, air Variables would include temperature, moisture, air

movementmovement

The Earth-Sun Relationship The Earth-Sun Relationship (p.55)(p.55)

The sun provides enough heat to The sun provides enough heat to energize Earth and keep it warm.energize Earth and keep it warm.

The Earth-Sun RelationshipThe Earth-Sun Relationship The sun exerts a The sun exerts a gravitational pull gravitational pull on the on the

Earth, so Earth Earth, so Earth revolvesrevolves around the sun. around the sun.

The Earth-Sun RelationshipThe Earth-Sun Relationship The Earth is The Earth is tiltedtilted in its in its

orbit, which partially orbit, which partially explains the patterns of explains the patterns of day and night and the day and night and the seasons.seasons. Because of the tilt, there Because of the tilt, there

are only 2 times a year are only 2 times a year when the sun shines when the sun shines equally on both equally on both hemispheres; March 20-hemispheres; March 20-23 and September 20-23. 23 and September 20-23. These are called These are called

equinoxesequinoxes..

Patterns in TemperaturePatterns in Temperature The range between daytime The range between daytime

and nighttime temperatures and nighttime temperatures results from: results from: The amount of cloud cover in The amount of cloud cover in

the skythe sky The earth’s curvatureThe earth’s curvature

At the equator, sunlight At the equator, sunlight comes comes directlydirectly through through the atmosphere and the atmosphere and strikes the earth strikes the earth directly, hitting a small directly, hitting a small area (fig 4.3, E)area (fig 4.3, E)

Away from the Away from the equator, sunlight equator, sunlight comes through the comes through the atmosphere at an atmosphere at an angle angle and strikes the earth and strikes the earth indirectly, hitting a indirectly, hitting a larger area (fig. 4.3, F)larger area (fig. 4.3, F)

Wind: The Movement of AirWind: The Movement of Air

Air Circulation Pattern:Air Circulation Pattern: The air above the equator The air above the equator

heats up rapidly and rises, heats up rapidly and rises, pushing cooler air towards the pushing cooler air towards the north and south poles.north and south poles.

The cooler this air gets, the The cooler this air gets, the more it sinks. As it sinks, it more it sinks. As it sinks, it heats up and forces cooler air heats up and forces cooler air back towards the equator…back towards the equator…and the pattern repeats…and the pattern repeats…

The movement pattern is The movement pattern is called a called a convection cellconvection cell, , which more evenly distributes which more evenly distributes heat around the world.heat around the world.

Convection Cells

Wind: The Movement of AirWind: The Movement of Air

Convection is driven by air Convection is driven by air density:density: Warm, moist air is Warm, moist air is less less

densedense and it and it floatsfloats ==LowLow pressure areas pressure areas

Cold, dry air is Cold, dry air is densedense and it and it

sinkssinks ==HighHigh pressure areas pressure areas

WindWind is created when air is created when air

movesmoves from high pressure from high pressure areas to low pressure areasareas to low pressure areas

Questions: # 15 & 16, pages Questions: # 15 & 16, pages 61-62.61-62.

Wind: The Movement of AirWind: The Movement of Air

Prevailing WindsPrevailing Winds There are 6 convection cells which create a series There are 6 convection cells which create a series

of high and low pressure belts around the earth of high and low pressure belts around the earth between which the wind blows. These wind between which the wind blows. These wind patterns are constant and predictablepatterns are constant and predictable

Trade WindsTrade Winds WesterliesWesterlies Polar EasterliesPolar Easterlies

Wind: The Movement of AirWind: The Movement of Air

Wind: The Movement of AirWind: The Movement of Air

Prevailing Winds (…continued)Prevailing Winds (…continued) Two factors change how prevailing winds blow:Two factors change how prevailing winds blow:

Variations in the Earth’s surface (constant).Variations in the Earth’s surface (constant). The Earth’s position relative to the sun (varies by The Earth’s position relative to the sun (varies by

season)season)

Wind: The Movement of AirWind: The Movement of Air

Prevailing Winds (…continued)Prevailing Winds (…continued) Two factors complicate the pattern of convection Two factors complicate the pattern of convection

currents:currents: The Earth’s surfaceThe Earth’s surface The uneven distribution of land and water over the Earth’s The uneven distribution of land and water over the Earth’s

surfacesurface

Two factors complicate the pattern of convection Two factors complicate the pattern of convection currents:currents:

The Earth’s surfaceThe Earth’s surface The uneven distribution of land and water over the Earth’s The uneven distribution of land and water over the Earth’s

surfacesurface

Wind: The Movement of AirWind: The Movement of Air

Prevailing Winds Prevailing Winds (…continued)(…continued)

Each hemisphere is Each hemisphere is broken up into 3 broken up into 3 different convection different convection cells (fig 4.10, p.63):cells (fig 4.10, p.63):

0-23.5 degrees 0-23.5 degrees latitudelatitude

23.5-66.5 degrees 23.5-66.5 degrees latitudelatitude

66.5-polar latitude66.5-polar latitude

Wind: The Movement of AirWind: The Movement of Air

Wind & Precipitation Patterns:Wind & Precipitation Patterns: Humidity:Humidity: amount of moisture in the air; it comes from the earth’s amount of moisture in the air; it comes from the earth’s

surface and evaporates into the atmosphere.surface and evaporates into the atmosphere.

Wind: The Movement of AirWind: The Movement of Air

Wind & Precipitation Wind & Precipitation Patterns (continued…)Patterns (continued…) 2 Basic Principles 2 Basic Principles

about Precipitationabout Precipitation::

1.1. When warm air cools, it When warm air cools, it cannot hold as much cannot hold as much water vapour.water vapour.

2.2. Temperature rises as air Temperature rises as air pressure increases; it pressure increases; it lowers as air pressure lowers as air pressure decreases.decreases.

*Do questions 22-26, p.64-67**Do questions 22-26, p.64-67*

Other Factors Affecting ClimateOther Factors Affecting Climate Ocean Currents: Ocean Currents: permanent or semi-permanent permanent or semi-permanent

horizontal movement of unusually cold or warm surface horizontal movement of unusually cold or warm surface water of the oceans, to a depth of about 100mwater of the oceans, to a depth of about 100m.. The primary The primary cause of ocean currents is the global movement of cause of ocean currents is the global movement of windswinds..

Three main factors influence how and where ocean Three main factors influence how and where ocean currents flow…currents flow…

Other Factors Affecting ClimateOther Factors Affecting ClimateOcean CurrentsOcean Currents

1. 1. Coriolis EffectCoriolis Effect: ocean : ocean currents shift left or right currents shift left or right depending on the depending on the hemisphere they’re in.hemisphere they’re in.

Other Factors Affecting ClimateOther Factors Affecting ClimateOcean CurrentsOcean Currents

2. The Size and 2. The Size and shapeshape of the of the body of water in which body of water in which they develop.they develop.

Ex. The Gulf Stream is Ex. The Gulf Stream is deflected northeast by the deflected northeast by the shape of the North shape of the North American coastline.American coastline.

Other Factors Affecting ClimateOther Factors Affecting ClimateOcean CurrentsOcean Currents

3. Differences in 3. Differences in water temperaturewater temperature and and salt contentsalt content (remember the effect this had in, ‘The Day After (remember the effect this had in, ‘The Day After Tomorrow’?).Tomorrow’?).

These differences cause These differences cause convection currentsconvection currents similar similar to those in the atmosphere.to those in the atmosphere.

Other Factors Affecting ClimateOther Factors Affecting ClimateOcean CurrentsOcean Currents

Other Factors Affecting ClimateOther Factors Affecting ClimateOcean CurrentsOcean Currents

Section questions: 27-30, pages 68-69Section questions: 27-30, pages 68-69

Other Factors Affecting ClimateOther Factors Affecting Climate

ContinentalityContinentality Water heats up and cools down more slowly than Water heats up and cools down more slowly than

land. land. Areas near large bodies of water (Vancouver, Areas near large bodies of water (Vancouver,

Botwood) have a Botwood) have a maritime climatemaritime climate; the ; the temperature ranges are small and they have more temperature ranges are small and they have more precipitation.precipitation.

Areas far away from water (Calgary, Buchans) Areas far away from water (Calgary, Buchans) have a have a continental climatecontinental climate; the temp. ranges are ; the temp. ranges are large and they have less precipitation.large and they have less precipitation.

Other Factors Affecting ClimateOther Factors Affecting Climate

Continentality and Wind PatternsContinentality and Wind Patterns Because the sun’s heat is retained differently by Because the sun’s heat is retained differently by

land and water…land and water… Winds blow differently in Winds blow differently in coastalcoastal areas than in areas than in

continentalcontinental areas. areas. Winds blow differently inWinds blow differently in mountainous mountainous areas than on areas than on

the the plains.plains.

Other Factors Affecting ClimateOther Factors Affecting Climate

Elevation and ClimateElevation and Climate =height above sea level…the higher it is, the =height above sea level…the higher it is, the

colder the climate is.colder the climate is.

Other Factors Affecting ClimateOther Factors Affecting Climate

Elevation also affects Elevation also affects precipitation:precipitation: Clouds must rise to pass Clouds must rise to pass

over mountains. As they over mountains. As they do, the water vapour in do, the water vapour in them condenses and them condenses and rain/snow falls on the rain/snow falls on the windward side. The windward side. The leeward side (rain leeward side (rain shadow) receives little shadow) receives little precipitation.precipitation.

Other Factors Affecting ClimateOther Factors Affecting Climate

Elevation and ClimateElevation and Climate Section Questions: page 71-72, #36b., 37, 38, 39,Section Questions: page 71-72, #36b., 37, 38, 39, Chapter review questions: page 72, # 40-41Chapter review questions: page 72, # 40-41