Wind is the horizontal movement of air from areas of high pressure to areas of low pressure
Moderates temperatures
distributes moisture
cleans the atmosphere
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So why don't we feel it?
Air pressure is exerted in all directions (think of a bubble)
All the forces are in balance at Earth's surface
As elevation increases, air pressure decreases
We can usually only feel changes in air pressure when we fly in a plane, go up an elevator quickly, or experience some other rapid change in air pressure
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Barometers measure air pressure
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Barometers measure air pressure in inches/millimeters and millibars
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Elevation
Temperature
Humidity
changingmatter.mht
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Meteorologists can analyze air pressure by gathering data on air pressure at different points. (such as the United States)
The data points that exhibit the same air pressure are connected by a line. These lines are called isobars
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Think of it this way....
If there was a mountain, and you wanted to see how steep it was by looking at a map you could connect points on the map with the same elevation. It would end up looking something like this
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Where the lines are close together, the change in elevation is quick, indicating a steep slope
Where the lines are farther apart, there is a more gentle slope because the change in elevation is more gradual
You can see how a 2­D map can depict 3­D image if you look at it properly.
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When isobars are close together, there is a dramatic change in air pressure which will create strong winds.
Where isobars are farther apart, or far apart, there is a more gradual change in air pressure which will result in light breezes or calm conditions
The change in air pressure from one point to another as indicated on a weather map is called a pressure gradient
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19­2 notes
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coriolis effect
pressure gradient
friction
affect
wind
direction
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winds will be turned to the
right in the northern
hemisphere, and the left in
the southern hemisphere
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1904/es1904page01.cf
m?chapter_no=visualization
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http://www.classzone.com/books/earth_science/terc/content/visualizations/es1905/es1905page01.cf
m?chapter_no=visualization
We have learned that air will
ALWAYS move from areas of high
pressure to areas of low pressure
(in a straight line)
However.......
Because the Coriolis effect deflects winds to the right in
the northern hemisphere, winds will rarely travel in a
straight line from a high pressure area to a low pressure
area, the winds actual path will be deflected to the right
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(30 degree deflection)
Winds are deflected to the right of the direction the wind is traveling
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(30 degree deflection)
Winds are deflected to the right of the direction the wind is traveling
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Friction between the air and ground slows surface winds
The more friction there is, the less the wind will be
deflected (it will travel in a straighter line)
Fast moving winds will move more parallel to the
isobars (will travel in a more deflected, curve)
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http://www.classzone.com/books/earth_science/terc/content/investigations/es1906/es1906page01.cf
m?chapter_no=investigation
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19-3 notes
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(5 of them are)
1.
2.
3.
4.
5.
6.
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This is what winds would look like if they were on a non­rotating, ocean planet (no continents)
results in one
large circulation
cell in each
hemisphere
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But Earth rotates, and has huge land masses so­o­o­o­
ooooo.....
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.
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UPPER LEVEL WINDS
At this point the pressure gradient force and the coriolis force are in balance, causing the air to travel parallel to the isobars
1000mb
1004mb
1008mb
Air direction of motion
coriolis force
Pressure gradient force
A force that pushes air from high pressure to low pressure
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SURFACE WINDS
Friction (demonstrated by the small arrow going the opposite direction of the wind) causes the wind to be slowed down, which results in it blowing across the isobars at an angle and spin clockwise out of a high
1000mb
1004mb
1008mb
Air direction of motion
coriolis force
Pressure gradient force
A force that pushes air from high pressure to low pressure
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this is what the book says about it on page 420...
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Isobars are points on a map that connect points of the same air pressure
By connecting points of the same pressure on a weather map, areas of high and low pressure become visible. Because areas of high pressure and low pressure usually accompany certain weather, meteorologists are able to make predictions about what the weather might do.
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Winds will blow out of a high pressure system in a clockwise direction because they are turned to the right due to the coriolis effect
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Winds will blow counter­
clockwise into a low pressure system because they are being turned to the right by the coriolis effect
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LAB
In the lab you will be working on today, you will create isobars by reading a weather map with pressure readings on it, from there you will find the high and low pressure systems as well as determine where the wind is blowing both on the surface and in the upper atmosphere
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Land and sea breezes over the course of 24 hours...
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Land and sea breezes over the course of 24 hours...
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Why would the highest temps be north of the equator in the
N.H. in the summer?
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Continents heat more quickly than oceans
why???? (3 reasons)
Because the continents are significantly hotter than
the oceans they become areas of low pressure where
air is heated, rises and is replaced by more wind that
is heated and rises (on-going)
Air over the ocean (although humid) is significantly cooler
than the air over the land, creating a strong high pressure
system. Over the ocean, cold dense air sinks and is pulled
into the low pressure system
How do winds spiral into lows?
How do winds spiral out of highs?
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In the winter, the reverse is true. Because the oceans hold
onto their heat longer, they are warmer than the continents,
creating an area of low pressure. While the continents which
loose their heat quickly become much cooler than the oceans,
causing them to be the source of high pressure.
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