World Geography 3202
Unit 2: Patterns in Weather &
Climate
Chapter 4
WEATHER AND CLIMATE
Weather & Climate
Key Terms
1. Weather – the state of the atmosphere at any
one place or time, this includes humidity,
temperature, hours of sunshine, cloud clover,
visibility, and precipitation
2. Climate – the average weather conditions of a
region. The recorded average is the result of
many years of observations of weather.
Climate Graphs
Climate Graphs
• The right scale
indicates the
temperature and it is
graphed as a line (red
is common).
• The left scale is for
precipitation and is
graphed as a bar
graph ( blue is
common).
Elevation and Temperature 2.6
• Elevation is defined as the height of a region
above sea level
• Air temperature decreases 2ºC for every 300
m increase in elevation.
• The higher up we go the colder it gets (hence
snow on mountain tops)
Impact of Elevation and Temperature. For Example:
• La Paz, Bolivia, has an elevation of 3600m. Its
coldest month has an average temperature of
9ºC.
• Rio de Janeiro, Brazil, has an elevation of 61m. Its
coldest month has an average temperature of
25ºC.
• La Paz and Rio de Janeiro have a similar distance
from ocean and similar latitude. However, La Paz
is much colder because of higher elevation.
Elevation and Precipitation
Relief has an effect on precipitation mostly as it relates to
relief rain. Consequently it must be accompanied by
wind.
Relief Rainfall
• Moisture laden air blows off the sea;
• it is forced up by mountains (high relief);
• air cools at higher altitudes;
• cool air holds less moisture;
• clouds condense and rain falls;
• most rain falls on the windward side of the relief.
Rain Shadow
• The Leeward side of a mountain is often in a dry
rain shadow because the moisture has all been
lost.
Examples
• Many places like Vancouver receive large
amounts of rain because they are on the
windward side of the mountain.
• Other places like Edmonton receive very little rain
because they are on the leeward side of a
mountain range.
Climate Regions 2.7
Tropical Climates
• All Tropical Climates have average temperatures
over 18C every day due to low latitude, warm
ocean currents & prevailing winds.
• Viewing figure 5.1 on page 75 of your text you
can see that almost all of the tropical wet and the
tropical wet & dry climates are located between
the tropic of cancer and the tropic of Capricorn.
• You will notice on the climate graphs below that
the line indicating temperature is fairly flat, right
around 20C.
– Tropical wet:
• heavy rain all year due to hot temp &
resulting convectional rain
– Tropical wet & dry:
• very heavy summer rain & very dry
winter due to seasonal shift in
prevailing winds. (monsoon regions)
Dry Climates
• All Dry climates receive less than 500mm
precipitation annually.
• The region has more evaporation than
precipitation leaving it in a water deficit.
• There is little vegetation & it is often windy
• Climate graphs of arid and semi-arid regions
are difficult to distinguish from each other but
easy to distinguish from all other climates
because of the low precipitation bars.
– Semi-Arid or Steppe:
• transition zone between desert & Forest.
They receive 250-500mm rain annually
which is often enough
to
support
grasses but not forests
– Arid or Desert:
• occur mostly between 10 - 30N & 10 30S and receive 10 - 250mm rain
annually
Temperate Mild Winter Climates
• A review of figure 5.1 on page 75 of your text
reveals that temperate mild climates occur in
both hemispheres
• Temperature varies with seasons
• Mid Latitudes
• Mild winter
• Summer temperatures vary but winters are
warmer than –3 C
• The distinguishing feature on a climate graph is
the curved temperature line
– Mediterranean:
• occurs
in
areas
around
the
Mediterranean sea, as well as in small
west coast areas of California, Chile,
South Africa, and Australia
– Subtropical:
• This is the climatic region of Florida and
other parts of the American southeast, as
well as a large part of southeast China
and South America
– Marine West Coast:
• It is found on the west coasts, in high
latitudes, extending as far north as Alaska
and north Scandinavia, and far south as
New Zealand and the southern tip of South
America
Temperate Cold Winter Climates
• A review of figure 5.1 on page 75 of your text reveals
that temperate cold climates only occur in the
northern Hemisphere.
• Temperate cold Winter
• Temperature varies with seasons
• Mid-high Latitudes
• cold winters
• Summer temperatures vary but winters are colder than
–3 C
• The distinguishing feature on a climate graph is the
curved temperature line.
– Continental, Warm/Cool Summer:
• Occurs in much of southern Canada, the
American Midwest, all of New England,
much of northern Asia, and central
Europe
– Subarctic:
• Follows the same patterns as continental
climates, however, the main difference is
that winters are very long and extremely
cold
Polar Climates
• Polar climates are distinguished by their
extremely low winter temperatures and low
summer temperatures.
• On the northern edge of North America,
Europe, and Asia, as well as throughout
Antarctica.
• These locations have Earth’s coldest, driest,
and darkest winters.
– Tundra:
• This sub-region is closer to oceans,
therefore have less severe temperatures
– Icecap:
• This sub-region is inland thus with
increased cold brought about by
continentality
Highland Climates
• These climates are only characterized by their
elevation and decreased temperature because
of that. However the climates vary with
latitude of the mountain, closeness to the
ocean etc.
• Some alpine regions can be like the tundra
and the ice cap of a mountain is like the polar
ice caps.
– Upland:
• Chiefly characterized by the colder
conditions caused by high elevation (above
1000 m).
Climatic Conditions & Human Activity
2.8
Positive Influences of Climate
• Good tourist industry in subtropics like Florida;
• sports are affected: golf—summer, hockey—
winter;
• religious tradition of Christmas strongly
associated with winter conditions;
• clothes—fashion changes with the season;
• school closed during summer season in
temperate zone.
Negative Influences of Climate
• Transportation is affected;
• winter tires in temperate zone;
• snow clearing budgets can be high;
• school closed during winter storms in
temperate zone.
Global Warming
• Global warming is the gradual increase of the
earth's average temperature since the industrial
revolution.
• It is a fact that the earth's average temperature is
increasing. The negative effects associated with
global warming are also factual.
• Some scientists dispute the fact that it is due to
human activity. Some scientists believe the
recent increase in temperature is a part of the
normal rhythms of change in the earth's
atmosphere.
Global Warming vs. Greenhouse Effect
• It is also important to draw a distinction between
global warming and the greenhouse effect.
• The greenhouse effect is a good thing and
moderates our temperatures here on earth. It
operates by specific gases like carbon dioxide and
methane.
• Global warming is due to the human activity that
has increased the level of these greenhouse
gasses and consequently increased the earth's
temperature.
Human Impact on Greenhouse Gases
It is believed that humans have changed the balance of
greenhouse gasses in the atmosphere in two ways:
1. Increased carbon dioxide emissions due to the
combustion of fossil fuels. Coal, Gasoline, Furnace oil,
Propane, diesel, and jet fuel are all examples of fossil
fuels we burn and result in carbon dioxide emissions.
2. Cutting forests which results in fewer trees. Trees and
all plants recycle carbon dioxide into carbohydrates
consequently
reducing
atmospheric
carbon
dioxide. When these trees are removed the level of
carbon dioxide in the atmosphere increases.
Global Warming & Climate Change
Obviously global warming results in
temperature changes.
However that
temperature change affects precipitation as
well. In some areas it increases precipitation
and in other areas it reduces precipitation.