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Weather & Climate
Grade 10 Geography
Weather and Climate
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Weather is the daily occurrence of wind,
precipitation and temperature.
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Combination of temperature, precipitation, cloud
coverage, relative humidity, wind and atmospheric
pressure.
Climate is the averages of weather conditions
over a yearly or seasonal period of time.
Factors that affect climate and weather
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Factors that affect climate and weather are:
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wind
latitude
elevation
proximity to water (closeness to water)
ocean currents
aspect of the land (topography
Prevailing Wind
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In Canada we experience Westerlies – the
prevailing winds move air masses that affect
our weather – from West to East.
As air masses move over the Arctic in the
winter, it will be cold & dry. As it moves
southward, its cold dry conditions are carried
across Canada.
If an air mass comes from the Gulf of Mexico
it brings moist, warm conditions to Canada.
Latitude
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The further you move away from the equator,
in the north or south direction, the cooler it
becomes.
The sun’s energy is spread over a larger area
the more you move away.
Canada in relation to Central America
Elevation 
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Relief refers to the differences in elevation of
the Earth’s surface.
Mountain ranges act as barriers to the
movement of air masses.
Temperatures drop as you climb a mountain
– as the elevation increases the temperature
gets colder.
Air expands as it rises since there is less air
pressure.
Proximity to Water
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Oceans and large lakes heat up & cool down
more slowly than land masses.
In Summer – body of water remains cooler
that then land – winds blowing off the water
keep the surrounding land cooler.
In Winter – bodies of water retain their heat &
are warmer than the land. Winds blowing off
the water keep the surrounding land warmer.
Maritime climates therefore have cooler
summers & milder winters.
Ocean Currents
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Temperature of an ocean current affect the
temperature of air that passes over it.
West Coast – the warm North pacific Current
heats the cool moist air that passes over it =
mild climate on the costal region of BC.
East Coast – the cold Labrador Current,
cools the air of coastal location in Labrador
and Newfoundland.
Two types of climate:
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Maritime – near large bodies of water,
experience considerable amounts of
precipitation.
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Continental – seasonal precipitation and
temperature.
Three types of precipitation:
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Orographic precipitation (mountains)
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Frontal precipitation
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Convectional precipitation (circulation)
Orographic precipitation
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AKA Relief Precipitation
Rain or snow that results when air is cooled
as it is forced aloft by a topographic barrier
such as a mountain.
Common in British Columbia.
Frontal precipitation
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Occurs when colder air mass forces a
warmer air mass to rise.
Common in Atlantic Canada.
Convectional Precipitation
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Heating of the earth's surface that causes
air to rise rapidly. As the air rises, it cools
and moisture condenses into clouds and
precipitation.
Common in the Prairie Provinces.
Cloud Formation
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As air rises it cools, as it cools the air
particles condense and attach to dust
particles. As moisture continues to develop,
clouds are formed. Once the clouds reach the
saturation point (the point where the clouds
cannot hold anymore moisture) precipitation
occurs.
Hydrologic Cycle or Water Cycle
Saturation Point
Precipitation
(Water Cycle)
(Hydrologic Cycle)
Clouds Form
Air cools and condenses
(Condensation)
Hot Air Rises (Evaporation)
Land
Water
What Makes Weather?
Front – where warm air and cold air meet.
Stationary Front –
 Warm air and cold air move in opposite
directions where neither air mass is having
any force on the other.
 W 
  C
Warm Front –
 Warm air forces cold air out of the way.
 W   C
Cold Front –
 Cold air forces warm air out of the way.
 W   C
“Iso”
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If “Iso” means the same,
Then what are Isotherms?
Isobar?
Isohyets?
Isostatic rebound?
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Isotherms = Places that have the same
temperature.
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Isobar = Places that have the same
barometric pressure.
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Isohyets = Places that have the same
humidity.
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Isostatic rebound = Places that have the
same movement upward from the retreat of
the glaciers.
Cloud Classification
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Stratos – (sheet-like) above 6000m
Cumulus – (pile) 2000-6000m
Nimbus – (rain) – 500-2000m
Cirrus – (hairlike) – below 500m = fog
Cumulonimbus – large dark storm clouds
Barometric Pressure
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The amount of pressure the air is forcing
down to the ground. 101.3kPa (kilopascals)
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High pressure = sunny, clear skies
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Low pressure = cloudy, cooler temps &
precipitation
Chinook Wind
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A Chinook Wind occurs when enough heat
exists.
These warm winds often melt snow in the
fields and forest on the lower slopes.
Occurring near mountain ranges.
Can raise temperatures as much as 20°C to
30°C in a 24 hour period, and melt the
shallow snow.
Calgary experiences Chinooks.
High vs Low Pressure Belts
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The air is warm at the equator and rises, which
forms a belt of low pressure around the earth.
If it wasn't for the earth's rotation and the Coriolis
force, that air would then sink at the poles and form
two high pressure zones.
But it falls at roughly latitudes 30 N and 30 S. Those
are two belts of low pressure. Between those and
the polar ones, a front exists along which warmer air
rises over colder one.
That creates then two belts of high pressure at
roughly the latitudes 60 N and 60 S.
Hadley Cell
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The circulation between the equator and the
high pressure belts.
Trade winds
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Also called trades.
Surface winds found in the tropics within the
lower portion of the Earth's atmosphere.
Doldrums
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A band of air encircling the Earth just north of
the equator.
Where winds from the northern and southern
hemispheres meet.
Low pressure system
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Cloudy or stormy weather
Barometric pressure is lowered and a lowpressure system forms, it brings in air,
usually from a cold front to the north.
A strong low-pressure system in winter may
bring snow and ice to the areas it covers.
Tornadoes, have low air pressure inside their
funnels. Low pressure system over water can
lead to a Hurricane.