Copy of GlobalWinds,Worksheet
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Apr 3, 2024
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Global Winds Worksheet
Read the Explore
information and answer the Explain questions in your own words.
Explore: The winds in Indiana can blow from any direction on any given day, but weather systems almost always travel from the west to the east. If you look at the weather in Illinois today, you might expect that weather tomorrow in Indiana. That is because we live in an area called the Prevailing Westerlies where weather is pushed from west to east. The Earth has definite wind patterns. These patterns are a result of how the Sun heats the Earth combined with the rotation of the Earth. These wind patterns influence the types of climate around the world.
Explain: what do you think? (You do not have to know these answers!)
●
How might the Sun have an effect on global wind patterns?
I don’t know maybe the heat makes wind go a certain way
●
How might the rotation of the Earth affect global wind patterns?
Maybe the Earth rotating makes wind patterns rotate I dunno.
Explore
There must be a force that causes the air to move or we would not have
wind. Air that is moving across the surface of the earth is called wind.
The Sun heats the surface of the Earth and the surface heats the air. The
equator receives the most direct sunlight and the poles receive the least
amount of sunlight. The surface at the equator is very humid. Rain forests and ocean surfaces
are plentiful at the equator adding more humidity to the air. Humid air is
less dense than dry air, just as warmer air is less dense than cooler air.
The air at the poles is cooler and water vapor does not exist well in cooler
air. Therefore, the cool, dry air at the poles is much denser than the warm,
humid air at the equator.
Explain What You Learned:
●
Why is the air less dense at the equator than at the poles?
Because the surface at the equator is very humid and rain forests and
ocean surfaces are plentiful at the equator, adding more humidity to the air. Humid air is less dense than dry air, just like warmer air is less dense than cooler air. The air at the poles is cooler and water vapor doesn’t exist well in cooler air. Therefore, the cool, dry air at the poles is much denser than the warm, humid air at the equator.
●
In the above diagram labeled with the “EQUATOR”, why is the air rising?
Air near the equator is warmed and rises because it is less dense than the air around it.
●
How is the surface air moving; toward the equator or away from the equator?
Away from the equator.
●
How is upper air moving; toward the equator or away from the equator?
Towards the equator.
Explore
If global winds were only affected by the heating of the Sun, global
winds would look like this diagram. The Equator would become very
hot and humid causing that air to rise and flow toward the poles. At the
poles the air would cool and sink returning to the Equator along the
surface.
The Earth is
rotating and this prevents the air from traveling in a straight line. The Earth’s rotation forces the air to the right in the northern hemisphere and to the left in
the southern hemisphere resulting in a global pattern
described in the following diagram:
This creates six bands of circulation, three in the northern hemisphere and three in the southern hemisphere.
The diagram is labeled with three numbered areas with each named cell. The surface winds in each cell
are also named.
1.
The Hadley Cell
is named after George Hadley (1685-1768) an amateur meteorologist who suggested that they existed. The air rises at the equator (0°) and sinks at about 30° N and S latitude moving back toward the equator at the surface. These surface winds are called Trade Winds and are winds blowing generally from east to west. Hurricanes develop in the Trade Winds.
2.
The Ferrel Cell
, suggested by William Ferrel (1817-1891), describes the sinking air at 30° N and
S latitude as moving also northward. This northward surface air is deflected to the right by the Earth’s rotation becoming surface winds blowing generally from west to east. This area, between 30° latitude and 60° latitude, forms an area known as the Prevailing Westerlies (sometimes known as the Stormy Westerlies).
3.
The final cell in the diagram is known as the Polar Cell
. Here air rises at 60° latitude and moves toward the poles (90°) where the air cools and sinks. This results in surface winds moving generally from east to west known as the Polar Easterlies. The sinking air creates polar deserts,
but not like the deserts that you usually think of. The poles do not get a lot of snow, but the snow they do get builds up year after year into deep snow packs.
This creates a global system that seems very uniform, but several factors complicate the image. Landmasses, ocean currents, and seasonal changes cause this orderly global wind pattern to fluctuate.
Explain What You Learned:
●
What prevents simple global surface winds from blowing from the poles to the equator?
"The Coriolis effect" is the one that prevents wind from blowing in a straight line from the north pole to the equator.
●
Describe how air moves in the Hadley Cell region:
The air rises and cools at high altitudes, moves outward (towards the poles) and, eventually, descends
back to the surface.
●
Describe how air moves in the Ferrel Cell region:
Air near the surface flows poleward and eastward, while air higher in the atmosphere moves equatorward and westward.
●
Describe how air moves in the Polar Cell region:
At higher latitudes, the air rises and travels towards the poles. Once over the poles, the air sinks, forming areas of high atmospheric pressure called the polar highs. At the surface, air moves outward from the polar highs, creating east-blowing surface winds called polar easterlies.
Fill in the following table:
Convection Cell
Within
Latitudes:
Name of Surface winds:
Direction
of winds
Hadley
0° - 30°
Trade Winds
From East to West
Ferrel
30° - 60°
Prevailing Westerlies
From West to East
Polar
60° - 90°
Polar Easterlies
From East to West
Between each of these cells are areas of high and low pressure at the surface. Explore:
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At 0° latitude are the Doldrums
: Along the equator between the north and south Trade Winds there is a band of low pressure. Within this band of lifting air, there is very little surface wind. For this reason, sailing ships would get caught in this area and spend days waiting for enough wind to carry them out. This area became known as the doldrums as ships would slow and float aimlessly.
At 30° latitude are the Horse Latitudes
: Along 30° north and south latitude between the Trade Winds and the Prevailing Westerlies is an area of high pressure. Within this band of sinking air, there is very little surface wind. For this reason, sailing ships would get caught in this area and spend days waiting for enough wind to carry them out. In the centuries following Columbus’ voyage, sailing ships would cross this band of high pressure en route to the new world. They carried people and supplies along with horses. There were no horses in the new world and horses were essential to the Europeans as a mode of transportation. Sailing ships would get caught in these windless areas and as supplies began to disappear, the horses became dispensable and were the first to be abandoned. For this reason, this band became known as the horse latitudes. Because air is sinking along this band and because clouds do not form in sinking air, the major deserts of the world can be found at 60° latitude. Deserts form in areas where air is normally sinking, either along 60° latitude or on the lee side of mountains.
At 60° latitude are the Subpolar Lows
: Along 60° latitudes between the Prevailing Westerlies and the Polar Easterlies there is a band of low pressure. This is also an area vacant of surface winds but with no historic significance.
Explain what you learned:
●
Why is the area along the equator known as the doldrums?
Because the air circulates in an upward direction, there is often little surface wind in the ITCZ. That is
why sailors know that the area can calm sailing ships for weeks. And that is why they call it the doldrums.
●
Why do deserts form along 30° latitude?
Hot air from the equator rises, then cools, moisture is lost, and the dry air comes down at 30 degrees north and south
Label the diagram using the following
words: Horse Latitudes, Polar
easterlies, Trade Winds, Doldrums,
Prevailing Westerlies, and Subpolar
Low. On the globe, using arrows,
show the general direction of the wind
in each of the three areas.