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Understanding Climates
Many people confuse the weather of a place with its climate. It is true that weather and
climate both focus on temperature and precipitation, but they consider different time
periods. Climate isn't the same thing as weather. Weather is the condition of the
atmosphere over a short period of time – maybe hours to a few days. Climate is the
“average” of weather conditions for a particular location over a period of many years.
Weather can change dramatically in a just a few days or hours. Climate too can change,
but it takes years if not decades.
When people say that they live in a certain place because they like the weather, they
actually mean they live there because of the climate. They don’t live there because of the
weather; weather cannot be predicted accurately for more than a few days at best.
Currently people argue about how much the climate is changing, if at all. However, very
few people argue about the weather becoming more extreme, both in temperature and in
precipitation. Winters are having more warm spells. Likewise, summers are having more
cool spells than before. The planet is also experiencing more droughts and more severe
storms and floods. While the weather is getting more extreme, the climate is the average
over time; the data does not change so quickly for climate
studies.
PRECIPITATION
HOT
?
LIKE____________
LIKE_____________
______
COOL & DRY
?
LIKE______________
LIKE_____________
_____
______
Though there are some variations of these combinations of
temperature and precipitation, these are the four major groups. No matter what the
climate is though, the climates occur in predictable patterns around the world. These
patterns are affected by one, two, three, or up to all four factors. Once a person
understands these factors, they can predict what the climate of almost any place could be
(if given location and the physical geography of
the
place.)
The first of the factors that influences climate is
the Latitude of the place. As places get farther
from
the equator, the sun’s rays are less direct. As a
result, it gets cooler as you go closer to the
north and south poles. At the equator the
earth’s surface gets more of the sun’s energy
than
anywhere else on the planet. (See picture 1) This Picture 1
makes the equator the hottest place on the planet. Since hot air rises, the air at the
equator is constantly rising. As the air rises it cools, causing
clouds and eventually some kind of precipitation. A place where
the air is rising is known as a low pressure area. This explains
why many of the rainforests of the world are at the equator.
As the air rises from the equator, it must be replaced by air from
somewhere else. The air that moves in to the equator region comes
from the tropics. Now the air from the tropics must be replaced.
This “new” air to the tropics is the “old” air from the equator that has
Picture 2
WET
HOT & DRY
_______
COOL
all of the squares.)
DRY
TEMPERATURE
When looking at a place geographically, people are
concerned about the climate of a place. There are not that
many different climates around the world. And because
climates are caused by earth’s physical geography, many
of those climates occur in certain predictable patterns.
Essentially, climates are temperature and precipitation over
time. Therefore, climates around the world are either wet
or dry. They are also either hot or cool. If you combine
those effects, you get the following combinations as shown
in the diagram squares to the right. (Fill the rest in to complete
risen and cooled, causing it to descend to the earth’s surface. (See picture 2) This falling down
of the air masses occurs at the Tropics of Capricorn and Cancer,
or 23.5 degrees north and south. As this air falls it is drier air
and there are few clouds if any. This causes the skies to
constantly be clear and allows the sun to beat down all day long.
It is at this location, the tropics that the world’s major deserts
appear. Areas where the air is “coming down” creates areas of
high pressure.
A place’s latitude is also related to the Wind directions
of that place. From roughly 30 degrees north to 30 degrees
Pict 3 south the winds come from the east. Between 30 and 60
degrees north and between 30 and 60 degrees south the winds come from the west.
These winds are called prevailing winds. While winds themselves don’t make weather or
climate, they can bring the ‘effect’ of another area. (See picture 3)
Oceans and ocean currents are a third factor
that can affect a place’s climate. Oceans and their
currents provide moisture that fuels rainstorms. If the
winds are coming from off of the ocean, the winds will
always carry in the moisture of the water. The
opposite is true. If the winds are coming from large
land masses it will be dry (since there are no water
bodies for evaporation to occur.) Oceans moderate
the climate of any place if the wind is blowing the
ocean air over the landmass. If the ocean currents are
Pict. 4
coming from tropical regions it will keep the
temperature of the coast warmer. If the ocean currents are coming from polar regions, the
water will be colder. Therefore, the polar currents will keep the temperature of the coast
warmer. (See Picture 4.)
Picture 3
2
Topgraphy is the last of four factors that can influence a place’s climate.
Mountains are the type of topography that typically affects weather the most. Mountains
can actually have a huge impact on the climate of a whole area, not just in the mountains
themselves. Mountains create “walls” that the prevailing winds hit. The wind is forced to
rise as it crosses over them. This cools the air,
causing moisture to condense into clouds,
eventually creating some kind of precipitation.
This produces a wet climate on the windward
side of the mountains. On the leeward side, the
wind comes down the mountain. On the
leeward side of mountain the air is “coming
down” the mountain and “leaving”. This side of
the mountain is much drier than the windward
side. Rainforests often occur on windward sides
Pict. 5
of mountains. At the same time, deserts often
occur on the leeward side of mountain ranges. (See Picture 5.)
All four of these factors can affect the climate of a place. For many places like
Wisconsin, we are not affected by topography. Additionally, most of Wisconsin is not
affected by the effects of the “Ocean” (meaning Lake Michigan or Superior. As a result,
Wisconsin is only affected by one factor of climate. (Which one?) For other places,
however, winds can “bring in” dramatic changes in temperature and precipitation.
Likewise, large land forms change an area’s temperature and precipitation from what it
would normally be at that latitude. When trying to figure out why there for a place’s
climate, make sure to consider all four factors that make up climate.