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Weather
&
Climate
Chapter 6
Weather & Climate
Weather:
 Refers to the
current,
day-to-day,
short term
conditions
of the
atmosphere.
Weather & Climate
Weather:



Wind speed
Wind direction
Temperature
 Type of precipitation
 Amount of precipitation
 Cloud cover
 Humidity
 Air pressure
 Hours of sunshine.
Weather & Climate
Climate:
 Refers to the long
term trends /
patterns in the
weather for a
certain area.
 Different areas
experience
different climate.
 Monthly,
seasonal, yearly.
Climate OR Weather??
Do the following phrases refer to weather or climate?

Annual precipitation of 200 mm.
 Rain forecasted for tomorrow Tuesday.
 Normal July temperature averages 22˚ C
 Temperatures this week will range between 20
& 30˚C
Climate OR Weather??
Do the following phrases refer to weather or climate?

It was unusually hot this summer.
 Grand Falls-Windsor had 15 cm of snow this
past weekend.
 Vancouver has an annual frost free period of
233 days.
 Residents in Florida are preparing to take
shelter from a hurricane.
Factors that Affect Climate
1.
2.
3.
4.
5.
6.
Latitude
Ocean Currents
Winds / Air Masses
Elevation / Altitude
Relief (Mountain barriers)
Nearness to water
Scattergraphs
1. Latitude

The further you move away from
the equator the colder it gets.
 As latitude INCREASES –
temperature decreases!
 The closer you go towards the
equator the warmer it gets.
 As latitude DECREASES –
temperature increases!
1. Latitude (cont’d)
The reason for this is:
 The sun’s energy is concentrated
in small areas near the equator.
 Over larger areas further from
the equator…the earth’s shape!
 Therefore the farther from the
equator the sun’s energy spreads
over a larger area.
Intensity and Duration!!
2. Ocean Currents

Pages 58-59 Q 1-3.
 Warm versus cold ocean
currents.
 Areas near warm ocean currents
have temperatures warmer than
areas near colder ocean
currents.
2. Ocean Currents (cont’d)



Pages 58-59 Q 1-3.
Warm air over warm ocean
currents colliding with cold air over
cold ocean currents result in
precipitation such as FOG!
Ie. St. John’s, NL where the COLD
Labrador current collides with the
warmer Gulf Stream (See p. 60)
3. Wind

Understand the cause of
wind and how they affect
climate
What is Wind?
A wind is a horizontal movement of
air across a surface.
 Vertical movements are currents or
updrafts and downdrafts
 Caused by what????
 Heat versus cold!! This can be
related to convection cells.

What causes wind?
 Unequal heating
 Unequal heating causes pressure
differences
 Cold, heavy air sinks = high
pressure
 Warm, expanding air rises = low
pressure
 Winds blow from high to low
Know that air blows from areas of high
pressure to areas of low pressure.
 The statement is fact.
 Think:
1. Air inside a balloon

High and low pressures in the earth’s
atmosphere are responsible for wind




Define the terms wind &
prevailing wind.
Wind:
Is a horizontal movement of air across
a surface.
It results from air masses of different
temperatures and humidity lying next
to each other.
The resulting pressure variation
causes “wind” to blow from high
pressure areas to low pressure areas.
Prevailing Wind:

Is regular, predictable, normal wind
direction for a given area or region.

Caused by global convection cells.

Named after the direction from which
it comes
Prevailing Winds
Prevailing
Winds
Summary of Prevailing Wind

Global highs and lows are due to
uneven heating of the earth

Air moves FROM HIGH pressure TO
LOW pressure creating winds.
Describe Orographic rainfall
Leeward
Chinook
Windward

A relatively warm, moist air blows off the
sea
 It is forced up by mountains (high relief)
Orographic rainfall





Air cools at higher altitude
Cool air holds less moisture
Consequently clouds condense and
rain falls
Most rain falls on the windward side of
the relief
Leeward side is often in a dry rain
shadow because the moisture has all
been lost
Definitions



Windward
 The side of the mountain receiving the wind of the
water/ocean
 (consequently more precipitation as well)
Leeward
 The side of the mountain sheltered from the wind
 (consequently receives less precipitation)
Rain Shadow
 The area located on the leeward side of a mountain that
receives low amounts of precipitation.
 Mainly due to the air that descends on the leeward side
has “dumped” on the windward side.
Frontal rainfall / Cyclonic
•Weather
Front-2
fronts meet
FRONT
Warm, moist air
•Hence the
name
frontal
rain
Warm Moisture laden air meets cold air

Warm air is less dense & is forced up over
the cooler, more dense air

Frontal rainfall
Warm Moisture laden air cools at
higher altitude


Cool air holds less moisture
Consequently clouds condense
and rain falls

Describe Convectional rainfall
•Often
associated
with thunder
storms.
Air heated from the earth






Usually occurs in hot areas like tropics or continental
summer
Sun heats the earth causing large amounts of water to
evaporate
Hot air rises forming convection currents (hence the name)
Warm Moisture laden air cools at higher altitude
Cool air holds less moisture
Consequently clouds condense and rain falls