Ch. 17,   p. 490, #1-11

1.  What is standard sea-level pressure in millibars?  In inches of mercury?  In pounds per square inch?

A.  Standard sea level air pressure is 1013 mb (millibars), which is the same as 29.92 inches of mercury or 14.7 pounds per square inch.

2.  Mercury is 13 times heavier than water.  If you built a barometer using water rather than mercury, how tall would it have to be to record standard sea-level pressure (in centimeters of water)?

A.  Standard sea level pressure in centimeters equals 76 cm of mercury.  Thus, the height of standard sea level pressure if a water barometer is used would be 13 times higher, or 988 cm.

3.  Describe the principle of the aneroid barometer.

A.  An aneroid (without liquid) barometer consists of evacuated metal chambers that compress as air pressure increases and expands when air pressure decreases.

4.  What force is responsible for generating wind?

A.  The pressure gradient force causes winds to blow.  Winds blow from higher pressure to lower pressure; the bigger the pressure difference, the greater the wind speed.

5.  Write a generalization relating the spacing of isobars to the speed of wind.

A.  Closely spaced isobars indicate a strong wind;  widely spaced isobars indicate a light wind.

6.  How does the Coriolis effect modify air movement?

A.  The Coriolis effect (the deflective force of Earth's rotation) causes air to be deflected to the right of its path of motion in the Northern Hemisphere and to the left in the Southern Hemisphere.

7.  Contrast surface winds and upper-air winds in terms of speed and direction.

A.  Upper air winds generally parallel the isobars, the result of the pressure gradient force and the Coriolis effect balancing one another.  However, near Earth's surface, friction slows the winds.  Since the strength of the Coriolis effect is proportional to the wind speed, the Coriolis effect is diminished.  Consequently, the Coriolis effect can no longer offset the pressure gradient force, and the surface winds blow at an angle across the isobars.

8.  Describe the weather that usually accompanies a drop in barometric pressure and a rise in barometric pressure.

.  A drop in barometric pressure usually leads to rainy or stormy weather.  A rise in barometric pressure usually indicates clear skies.

9.  Sketch a diagram (isobars and wind arrows) showing the winds associated with surface cyclones and anticyclones in both the Northern and Southern hemispheres.

A.  see diagram 16.8, pg. 448.

10.  If you live in the Northern Hemisphere and are directly west of the center of a cyclone, what most probably will be the wind direction?  What will the wind direction be if you are west of an anticyclone?

A.  The winds west of a cyclone in the Northern Hemisphere would be northwest, and winds west of an anticyclone would be southeast.

11.  The following questions relate to the global pattern of air pressure and winds?

a)  The trade winds diverge from which pressure zone?

A.  The trade winds diverge from the subtropical highs

b)  Which prevailing wind belts converge in the stormy region known as the polar front?

A.  The westerlies and polar easterlies converge in the polar front.

c)  Which pressure belt is associated with the equator?

A.  The equatorial low pressure belt is associated with the equator.

Last update 3/11/2005

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