Download The Changing Weather

CHAPTER 3 :THE CHANGING WEATHER
 What Is a Snowstorm?
 Two factors are essential in the creation of a snowstorm: snow
and wind
 Snow forms when water vapour condenses at a temperature
below the freezing point. As it condenses it forms ice crystals
that join together and make snowflakes.
CHAPTER 3
THE CHANGING WEATHER
 Snow pg. 34
 Condensation:



the process by which moisture
in the air changes to liquid or
solid form. Examples are rain,
clouds, and snowflakes.
 Condensation occurs when moist air rises and cools. It then
forms clouds.
CHAPTER 3 : THE CHANGING WEATHER
 Snow Pg. 34
 Air may rise for several reasons: it may be blown
over high ground, it may be warmed from below and
rise, or it may be forced upward by a colder and
denser air mass.
 You may think that areas that get the greatest snowfalls
would see schools close most often however average snowfall
is not a reliable predictor of storms
CHAPTER 3
THE CHANGING WEATHER
 Snow pg. 34
 The second ingredient-wind-is essential to a storm.
 Snow drifting down in soft white flakes generally
does not pose much of a danger to traffic.
 However, propel that snow with fast-moving air and
it may become a blizzard that is hazardous to most
forms of transportation
CHAPTER 3: THE CHANGING
WEATHER
Wind pg. 36
Wind is air that is moving from
an area of high pressure to an
area of low pressure.
High Pressure: an atmospheric
condition caused by the sinking
of cool air
Low Pressure: an atmospheric
condition caused by rising of
warm air
CHAPTER 3 - THE CHANGING
WEATHER
 Wind pg. 36
 Hot air rises cool air sinks
 A warm surface will heat the air
above it causing it to rise. This
creates an area of low pressure
beneath the rising air.
 An area of high pressure occurs
when the cool air sinks towards
the earth’s surface and pushes the
air underneath it away.
You're well familiar with our "H" and
CHAPTER 3
"L" designations on weather maps for
THE CHANGING WEATHERareas of high and low pressure, but
what do they mean in regards to what
weather's coming?
High pressure situations are generally
associated with fair, sunny weather.
As high pressure is an area of sinking
air, and air tends to dry out as it sinks,
leaving sunny skies.
Low pressure areas are generally
cloudy/rainy areas -- where strong
areas of low pressure bring our
stormiest weather. That's because it's
an area of rising air, and as air rises,
it condenses into clouds and rain. Air
moves from higher pressure to lower
pressure, so if you have a high and a
low nearby, it can be windy as air
rushes between the two
CHAPTER 3
THE CHANGING WEATHER
http://www.ctv.ca/weather/
CHAPTER 3 : THE CHANGING WEATHER
 Air at the poles sinks because it is cold. Air at the equator rises
because it is warm.
 So how does that af fect weather in the Atlantic Region.
 These air masses do not stay in one place because of the
earth’s rotation.
CHAPTER 3: THE CHANGING WEATHER
 Climate: average conditions of temperature,
precipitation, humidity, air pressure, and wind
 Precipitation: rain, snow, and any other forms
of water particles that fall from the atmosphere
 Weather: conditions of the atmosphere over a short
period
CHAPTER 3: THE CHANGING WEATHER
4 Factors That Influence the Climate of Atlantic Canada:
1)
2)
3)
4)
Latitude
Air masses
Ocean currents
Proximity to water
CHAPTER 3 : THE CHANGING WEATHER

All parts of the world
receive the same
total number of
daylight hours over a
year.

The earth’s surface is
curved so sunshine is
more intense in lower
latitudes
How does this influence climate? Cape Sable, Nova Scotia at
43*N receives more intense sun than Killinek, Labrador at 60*N
CHAPTER 3 : THE CHANGING WEATHER
Air Masses are…
large volumes of air with similar temperature and
moisture conditions throughout
Air masses take on the temperature and humidity
characteristics of the areas in which they
originate
For example, when Maritime Tropical air comes in
from the Caribbean it feels warm and moist
Air masses, like wind, move because of changing
pressure
CHAPTER 3 : THE CHANGING WEATHER
The leading edge of an air mass is known as a
front.
Front: The leading edge of an air mass,
bringing characteristics of the air mass;
they often result in a change in
temperature
Most precipitation in the Atlantic Region
comes about when cold dry air from the north
meets warm moist air from the south.
CHAPTER 3 : THE CHANGING WEATHER
Ocean Currents: the movement of water in the world’s oceans
 Water in the oceans is constantly in motion; tides move the
water up and down-ocean currents move water from place to
place.
 The two currents that af fect the Atlantic Region most are the
Gulf Stream and the Labrador Current
CHAPTER 3 : THE CHANGING WEATHER
Gulf Stream: an Atlantic
Ocean current from
the south; it brings warmth
to the southwestern waters
of the Atlantic provinces
Labrador Current: an ocean
current from the north; it
brings cold waters to much
of the Atlantic coast
CHAPTER 3 : THE CHANGING WEATHER
When the two currents meet fog is often the Result.
The warm moist air of the Gulf Stream Is cooled and
condenses.
The water vapor droplets are not large enough to fall
as rain so they remain suspended in the slowly
moving air.
CHAPTER 3 : THE CHANGING WEATHER
4/ Proximity to the Ocean
Sunshine heats land and water at different rates:
 Water, and the air over it, heats up and cools
down more slowly than land.
 As a result areas close to large bodies of water
stay cooler in the summer and warmer in the
winter than areas that are inland
 This affects the climate of many Atlantic towns
close to the ocean.