Chapter 6 Climate

Climate

Canada's climate is not as cold all year

around as some may believe. In winter,

temperatures fall below freezing point

throughout most of Canada. But the south-

western coast has a relatively mild climate.

Along the Arctic Circle, mean temperatures

are below freezing for seven months a year.

Climate

During the summer months the southern

provinces often experience high levels of

humidity and temperatures that can surpass

30 degrees Celsius regularly.

Western and south-eastern Canada

experience high rainfall, but the Prairies are

dry with 250 mm to 500 mm of rain every

year.

Weather/Climate

Weather

– Is the result of the day-to-day conditions of the

atmosphere.

Climate

– A long term pattern of weather

– Climate Is The Weather + Weather + More

Weather

Climate is what you expect, weather is what you get!

Weather

Types of things given in a weather forecast:

– Temperature Precipitation

– Humidity Wind speed/direction

– Cloud cover Air pressure

Climate Factors that affect climate (J.BLOWER);

– Jet Stream (air masses)

– Bodies of water

– Latitude

– Ocean Currents

– Winds

– Elevation

– Relief

Note: Different parts of Canada have different climates.

Factors that affect Climate

A. Jet Stream (Air Masses)

Air Masses -- is a large body of air that

has similar temperature and moisture

properties throughout.

For example: Winds blowing from a cold region will bring

cold temperature conditions to an area over which they

pass

Factors that affect Climate

B. Bodies of water

– Water warms up more slowly than land and cools off more slowly

– As a result of this, land near bodies of water are affected by the weather over these bodies of water.

Factors that affect Climate

Bodies of water

– The ocean make the temperature on land

cooler in summer and warmer in winter.

–This is called a maritime

climate.

Factors that affect Climate

Bodies of water

– Continental Climate— Land in the

interiors are not influenced by the sea and

experience extremely cold winter and hot

summers. PG 63 This climate is characterized by winter temperatures cold

enough to support a fixed period of stable snow cover

each year, and relatively moderate precipitation

occurring mostly in summer,

Factors that affect Climate

C. Latitude

– Distance from the equator

Angle at which sun rays strike the earth

Length of daylight period

The tilt of the earth’s axis combined with the

earth’s rotation in orbit around the sun

results in different day lengths.

Factors that affect Climate

D. Ocean Currents

– The movement of large quantities of ocean

water due to the unequal heating of the top

layer of the water by the sun.

– For countries on the east side of the Atlantic, winters are a

balmy holiday compared with the same latitudes on the west:

the frigid coasts of Newfoundland and Labrador.

Factors that affect Climate

Ocean Currents

– There are warm ocean currents and cold ocean

currents. These currents affect the air above

them in two ways:

Warming or cooling air masses

Warm air absorbs moisture, cold air does not absorb

moisture.

Factors that affect Climate

E. WINDS

– Wind is the flow of air.

– Created by differences in air pressure

– Winds are also caused by temperature

differences

Note: Differences in air pressure produce

convection currents and wind

Factors that affect Climate

Prevailing Winds

– are the trends in speed and direction of wind

over a particular point on the earth's surface.

– Canada’s prevailing wind pattern blows from

west to east.

– Prevailing winds bring different types of weather

and are the causes of waves as they push the

ocean.

Factors that affect Climate

Prevailing Winds

– The direction of wind is measured in terms

of where the air is coming from.

– A northerly wind blows air from north to

south. A southwesterly wind blows air from

the southwest to the northeast.

Factors that affect Climate

F. Elevation: the height above sea level.

– Virtually anywhere that has a high elevation will be colder than lower elevations at the same latitude.

– As air rises it expands because there is less air pressure (cont.)

– As air expands it becomes less

dense and less dense air holds less

heat than dense air, so the farther

above sea level you are, the lower the

temperature will be.

– The rate of cooling varies according

to the moisture content of the air.

– When air has a relative humidity of

100%, condensation begins and this

affects the cooling rate.

Factors that affect Climate

Air pressure

Air at sea level is what we're used to, in

fact, we're so used to it that we forget we're

actually feeling air pressure all the time!

Less air pressure at high altitudes than at

sea level.

How much pressure are you under? – Earth's atmosphere is pressing against each

square inch of you with a force of 1 kilogram per

square centimeter (14.7 pounds per square inch).

The force on 1,000 square centimeters (a little

larger than a square foot) is about a ton!

Why doesn't all that pressure squash

me? – Remember that you have air inside your body too,

that air balances out the pressure outside so you stay

nice and firm and not squishy.

Elevation

When condensation is not occurring, an air

mass loses 1c0 for every 100 m it rises.

When condensation is occurring, an air

mass loses 0.6c0 for every 100 m it rises. Diagram of air rising up a mountain

Factors that affect Climate

G. Relief

–Refers to the difference in elevation

of the earths surface.

–Mountain ranges affect climate

because they act as barriers to the

movement of air masses.

Factors that affect Climate

Relief – Mountain barriers also tend to cause

precipitation to occur.

Factors that affect Climate

Sea breezes

Factors that affect Climate

Sea breezes

– During the day the land becomes warmer than

the sea.

– A low pressure system is created over the land

and a high pressure system is created over the

sea.

– Winds move from highs to lows

– Therefore the winds move from the cooler water

towards the land creating a sea breeze

Factors that affect Climate

Land breeze

Factors that affect Climate

Land breeze

– During the night the land cools faster than the

sea.

– A high pressure system is created over the land

and a low pressure system is created over the

sea.

– Winds move from highs to lows

– Therefore the winds move from the cooler land

towards the sea creating a land breeze

Types of Precipitation

Precipitation

– is any product of the condensation of

atmospheric water vapor that is deposited on

the earth's surface.

Precipitation that reaches the surface of the

earth can occur in many different forms,

including rain, freezing rain, drizzle, snow,

sleet, and hail.

Types of Precipitation

1. Relief Precipitation (orographic)

2. Convectional Precipitation

3. Cyclonic/Frontal Precipitation

Relief Precipitation

Occurs when an air mass is forced from a

low elevation to a higher elevation as it

moves over rising terrain

Relief Precipitation

As the air mass rises it expands and cools.

This cooler air cannot hold the moisture as

well as warm air can.

When the dew point is reached the air

becomes saturated with water vapor and

condensation occurs, creating clouds and

frequent precipitation.

Relief Precipitation

As the cool air descends on the leeward

slope of the mountain it gets warmer.

Since warm air is able to hold more water

vapour than cooler air, the clouds

decapitates and the relative humidity drops

creating rain shadow conditions.

Evaporation rather than condensation

occurs.

Relief Precipitation

Convectional Precipitation

Develops as a result of uneven heating of

the earth’s surfaces by the sun.

Air above this area becomes warmer than

the surrounding air and starts to rise

This process creates convection currents or

updrafts

Convectional Precipitation

The rising air expands and cools, and water

vapour condenses to form clouds

Water droplets get larger and eventually the

weight forces them to fall.

As the precipitation reaches the ground it

cool it and the air and stops more updrafts

from forming.

Convectional Precipitation

Cyclonic/Frontal Rainfall

Warm Moisture laden air meets cold air;

Warm air is less dense & is forced up over

the cooler, more dense air;

Warm moisture laden air cools at higher

altitude;

Cool air holds less moisture;

Clouds condense and rain falls.

Cyclonic/Frontal Precipitation

A Cyclonic storm is a large low pressure cell

that forms when a warm air mass and a cold

air mass collide.

In Canada these low pressure storms move

from west to east at all times of the year.

Cyclonic/Frontal Precipitation

Interpreting Climate Graphs

What is a climate graph?

•a type of chart or graph that displays for a place the annual

pattern of the two most important climate variables:

precipitation and temperature

Precipitation is

shown by the

bars, with the

amounts on the

right Y-axis.

Temperature is

shown by the

line, with the

degrees on the

left Y-axis.

The data shown are

monthly averages,

with the months

across the X-axis.

Of what value are climate graphs?

•Climate graphs can be used to compare the climate of

selected locations quickly and simply.

•Especially useful to tell if a place has a continental or a

maritime climate.

•Continental: low annual precipitation; large annual

temperature range because of no moderating effect of a

large a body of water.

•Maritime: high annual precipitation; low annual

temperature range because of the moderating effect of

large a large body of water.

High annual precipitation,

with no seasonal

maximum.

Low (fairly low) annual

temperature range.

Winters are mild.

Summers are not hot.

Therefore, it’s a maritime

climate.

Moncton, NB

Low annual precipitation

High annual temperature

range

Therefore, continental climate.

Yellowknife, NWT

Fairly low annual

precipitation

Large annual temperature

range

Therefore, continental

climate

Timmins, ON

Very low annual

precipitation

Large annual temperature

range

Therefore, continental

climate

Resolute, NWT

Very low annual

precipitation

Large annual temperature

range

Therefore, continental

climate

Wait a minute …..!

Resolute is on water yet it

has a continental climate.

How come?

Because the water it is on

(the Arctic Ocean) is frozen

9 months of the year and so

acts like a land area.

Resolute, NWT

Fairly high annual

precipitation

Fairly low annual

temperature range

Therefore, maritime

climate.

Toronto, huh?

While “the T Dot” is in the

interior of North America,

Lake Ontario moderates

the temperature and

causes slightly more

precipitation.

Toronto, ON

Small annual precipitation.

Large annual temperature

range.

Therefore, continental

climate

Regina, SK

Fairly low annual

precipitation

Fairly high annual

temperature range.

Therefore, continental

climate.

Prince George, BC

Very high annual

precipitation

Very low annual

temperature range

Therefore, maritime climate.

Now, do the handout.

Canada’s Climatic Regions

Areas with similar climates:

– West Coast (maritime climate)

– Mountain

– Prairie (continental climate)

– Boreal (continental climate)

– Arctic (mainly continental climate)

– Southeastern (continental & maritime climate)

– East Coast (maritime climate)

Canada’s Climatic Regions

West Coast (maritime climate)

– Usually mild and greatly affected by the

Pacific Ocean

Canada’s Climatic Regions

Mountain (much variation)

– Differences in elevation

– Windward and leeward slopes

Canada’s Climatic Regions

Prairie (continental climate)

– Cool in winter, warm summers

– In the rain shadow of the Western Cordillera

– Precipitation from convectional precipitation

Canada’s Climatic Regions

Boreal (continental climate)

– Northern locations and interior positions

– Short summers & long winters

– Mainly convectional precipitation

Canada’s Climatic Regions

Arctic (mainly continental climate)

– Very harsh climate

– Cold desert

– Less than 350 mm of precipitation each year

– Long cold winters (10 Months)

Canada’s Climatic Regions

Southeastern (continental & maritime

climate)

– Climate affected by Great Lakes and Atlantic

Ocean

– Cyclonic precipitation caused by westerly winds

– Southerly storms formed in the Gulf of Mexico

Canada’s Climatic Regions

East Coast (maritime climate)

– Cold Labrador current meets warm Gulf of

Mexico current causes a lot of fog

– Winters not very cold

– Summers not very hot

– Receives more than 1000mm of precipitation.