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Canadian Geography

Chapter 4 Climate

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1. Weather- is the combination of temperature, precipitation , cloud cover and wind that we experience each day.

Ex. 22 degrees , clear skies.

Climate- is the long-term patterns of weather conditions.

Ex. Vancouver has an annual frost –free period of 233 days.

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2. Five Factors that influence climate: a. Latitude

b. Air masses

c. Altitude

d. Landforms

e. Nearness to water

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2a. Latitude- how far north or south a region is from the Equator influence how cold or warm it is.

This is the most important thing that affects climate. All climate stems from the equator (0° latitude). This is the hottest place on earth. As you go north or south from this line it becomes colder as you travel towards the North and South Poles.

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Notes: the amount of heat energy, or radiation, that the earth receives depends on the angle of the sun’s rays.

- if the angle creates a larger area than this will cause a lowering of temperature.

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4. Earth’s Rotation Around the Sun

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- the earth is tilted at an angle of 23.5 degrees.

- the earth rotates around the sun every 365.25 days.

- By June 21st , the Northern Hemisphere is tilted toward the sun . This means that the angle at which the sun’s energy reaches places like Canada is less than at other times of the year. Thus we receive our warmest temperatures in the summer.

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- By Dec 22nd the opposite occurs. The Northern Hemisphere is pointed away from the sun thus the angle the sun’s rays reach Canada is greater. Thus we receive our coldest temperatures during winter.

Note: A. When the sun’s rays pass through the

atmosphere , it absorbs up to 15% of the radiation.

B. Heat energy is also reflected back into the atmosphere as light . This reflectivity is called albedo.

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Case Study : Seasons

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Air Mass – is a large body of air with a uniform moisture and temperature content. Whether an air mass is warm or cold depends on where it originates.

- Each air mass has a two letter label. The first letter indicates whether the air is wet ; the second letter indicates the temperature.

5. Air Masses

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Note: Copy figure 4.8 pg. 52 into notebook.

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- Jet Stream- is a river of air that moves from west to east at speeds between 300 and 400 k m/h , at an altitude between 8000 and 15 000 m.

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- Most of the winds in Canada are called Westerlies because they flow from west to east.

- The leading edge of an air mass is called a front. Where two fronts meet often a battleground is created . Air masses don’t mix well.

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6. Cyclonic or Frontal Precipitation

Precipitation is created when a warm , moist body of air is forced to rise by a cooler body of air. As the air rises , it begins to cool. Cold air does not hold moisture as well as warm air . As, a result the water vapour in the cooling air condenses into droplets. These droplets form clouds and eventually they become to heavy for the air to hold and thus fall as rain or snow. ( Refer to pg.54 for diagram)

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7. Altitude

Altitude or elevation , affects both temperature and precipitation. Temperature decreases as altitude increases. So the farther up the air is from the ground , the cooler it is. The temperature for , dry air decreases 1 degrees C for every 100 m of altitude.

If the air is saturated with water vapour and condensation forms , it retains more warmth . This air cools down at a lower rate of 0.6 degrees C for every 100 m of altitude.

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Chinook- is a warm wind that flows from the Rocky Mountains across the foothills of Alberta during the winter time.

Chinooks—Warm West Winds

Along the eastern slopes of the Rockies, the Chinook wind provides a welcome respite from the long winter chill. Few people spend very much time along the eastern slopes without experiencing these wonderful warm winds. The change can be dramatic. On Jan. 11, 1983, the temperature in Calgary rose 30°C (from –17°C to 13°C) in 4 hours.

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8. Landforms

Landforms affect patterns of precipitation. They sometimes create barriers for warm and cold air reaching the land.

A. Orographic or Relief Rainfall( Fig.4.18 p.59)

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- This type of rainfall occurs when relatively warm, humid air is forced to rise over an elevated landform. (mountain)

- Rain Shadow- is the dry side or leeward side of a land mass.

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9. Nearness to Water

Large bodies of water influence climate. Water heats up and cools down more slowly than land thus during winter the water is warmer than summer in some areas.

A. Moderated temperature- is a climate created by the proximity of water that makes land temperature milder in winter and cooler in summer.

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B. Maritime Climate- is a climate with a small range between the maximum and minimum monthly temperatures , usually found in coastal locations.

C. Continental Climate- is a climate with a large range between the maximum and minimum monthly temperatures , usually found in the center of large land masses.

D. Temperature Range- is a calculation made by subtracting the coldest temperature from the warmest temperature.

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E. Land Breeze

During the night air cools and descends and the cool air moves seaward. Then the air above the water rises. ( Diagram p.61 right side)

1.Cool air over land sinks 2.Land Breeze moves out over water

3.Relatively warmer water heats air which then rises 4.Upper level return sea breeze

5.Cool air over land sinks

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F. Sea Breeze

During the day the air is cooling and descending and the cool air moves landward. The air is then heated over the land and rises. ( Diagram p.61 left side)

1.Warm air over land rises 2.Sea Breeze moves inland

3.Cumuli develop aloft and move seaward 4.Upper level return land breeze 5.Cool air aloft sinks over water 6.Sea Breeze (meso-cold) Front

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10. Convectional Precipitation

Stage 1The sun heats the ground and warm air rises. Stage 2

As the air rises it cools and water vapour condenses to form clouds.

Stage 3.When the condensation point is reached large cumulonimbus clouds are formed.

Stage 4.

Heavy rain storms occur. These usually include thunder and lightening due to the electrical charge created by unstable conditions.

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Is precipitation that occurs as a result of, warm moist air rising , then cooling and creating condensation . It often occurs on hot summer afternoons and evenings.( refer p.63. diagram 4.24)

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Animationhttp://62.239.5.6/vtc/Phase2delivery/NCA/Geography/Keystage3/Weatherandclimate/Factorsaffectingweatherandclimate/Factorsofweatherandclimate/Rainfall/Default.htm

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Terms:

A. Hailstones- is an ice pellet formed when a frozen raindrop is caught in violent updrafts in the atmosphere.

B. Hurricane- is a massive storm that produces heavy rain and winds exceeding 120km/h.

C. Tornadoes- is a destructive , rotating storm under a funnel – shaped cloud that advances across land at speeds of 50 to 100 km/h.

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D. Climagraph- is a combined line and bar graph showing average monthly temperature and precipitation.