Download Pressure: Highs and Lows

Pressure: Highs and Lows
Name: ___________________________
Date: _________________
Pressure is measured in milibars using a barometer. On a map we can look
for areas of similar pressure and connect them with lines. These lines are
called isobars. You will see many Isobars zigzagging across the U.S. on
the map. Notice that isobars curve and never cross each other!
If the numbers decrease as milibars move away from the center, it is a
high pressure system. If the numbers increase as milibars move away
from the center, it is a low pressure system.
1. Label the areas of high pressure centers with an H in the box and low pressure centers with an L in the box.
2. Based on yesterday’s research, what type of weather will they be having in Missouri (*)?
clear skies and sunshine OR cloudy skies and precipitation
3. Based on yesterday’s research, what type of weather will they be having in Montana (@)?
clear skies and sunshine OR cloudy skies and precipitation
@
*
CUA: The pressure in a high is greater than the surrounding air. Its winds
blow out. The pressure in a low is lower than the surrounding air so wind is
blowing inward. In the northern hemisphere the wind blows clockwise, called
an “anticyclone,” around centers of high pressure. The wind blows
counterclockwise, called a “cyclone” around lows. It is the opposite in the
southern hemisphere.
4. Label the wind systems on the right as cyclone and anticyclone.
5. Draw arrows for the wind directions on the map around the H and L of the high and low pressure systems.
Wind Strength
Remember that wind is the horizontal movement of air from an area of
high pressure to an area of lower pressure. The strength of the wind is
determined by changes in the pressure, called the pressure gradient. A
large change in pressure over a short distance (shown on a weather map as
lines very close together) would indicate strong winds. On a weather map,
isobars that are close together indicate a strong pressure gradient. The
drawing of the cyclone and anticyclone reminds you of the direction of the
wind within a pressure system.
Complete the map below again…it’s the same one as the front.
6. Label the area of high pressure centers with an H and low pressure centers with an L.
7. Indicate on your map where you expect the strongest winds with a large “S.” This is where the lines are
closest together.
8. Write an “A” next to the “S” if it is an anticyclone. Write an “AC next to the “S” if it is a cyclone.
9. Find Maryland on the map. Based on the systems you identified, describe the shift in wind and weather as the
system approaches you from west to east.
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Use the information and map below to answer questions 10-13.
The map below shows a low pressure system (labeled ‘L’) and a high pressure system (labeled ‘H’)
over the United States.
AIR PRESSURE SYSTEMS OVER THE UNITED STATES
H
L
10.
The large ‘H’ represents the center of a high pressure system. Which most likely describes the
properties of the air in the high pressure system?
A
B
C
D
warm, moist air
warm, dry air
cool, moist air
cool, dry air
12. The large ‘L’ represents the center of a low pressure system. Which best describes the vertical and
horizontal motions of air at the low pressure center?
A
B
C
D
13.
Winds along the surface between the pressure systems will generally move _______.
A
B
C
D
14.
Air is falling and moving inward at the surface.
Air is falling and spreading outward at the surface.
Air is rising and moving inward at the surface.
Air is rising and spreading outward at the surface.
from the high pressure center to the low pressure center
from the low pressure center to the high pressure center
from high elevations to low elevations
from the ocean to the continent
Which location is likely to have the greatest air pressure?
A
B
C
D
Top of Earth’s atmosphere
Upper surface of clouds
Middle of clouds
Surface of the Earth