Ch. 6 Questions for Review

8.) Why will Denver, Colorado, always have a lower station pressure than Chicago, Illinois?

It's because Denver is located at a higher elevation. The higher the elevation, the lower the pressure.

TE-7.) If the earth were not rotating, how would the wind blow with respect to centers of high and low pressure?

The rotation of earth generates the Coriolis force and friction that together deflect (bend) the winds. If earth did not rotate, winds would blow in straight lines from high-pressure areas to low-pressure areas (or perpendicular to isobars on a weather map) as predicted by Newton's laws.

16.) Explain how each of the following influences the Coriolis force: (a) wind speed, (b) latitude.

(a) The Coriolis force deflects moving air to the right in the northern hemisphere, and to the left in the southern hemisphere. (b) The magnitude of the deflection varies slightly with latitude. The Coriolis force is zero at the equator and increases as you move north or south reaching a maximum at the poles. Deflection also increases as wind speed increases.

3.) Why is the decrease of air pressure with increasing altitude more rapid when the air is cold?

Air temp. decreases (with exceptions) as you move up into the ATM. as does the atmospheric pressure. In fact, the temp. of the air affects the rate of pressure decrease as you move upward. Colder air is denser because the molecules of air are more closely packed together. As a result, pressure decreases more rapidly as you ascend through cold air than through warm air.

10.) On an upper-level map, is cold air aloft generally associated with low or high pressure? What about warm air aloft?

Cold air aloft is associated with a low-pressure system on the surface. Thus, there are two areas of low pressure in a low-pressure system. Warm air aloft is associated with high pressure.

2.) What might cause the air pressure to change at the bottom of an air column?

If the air at the bottom of the column is warmed, it will rise, and the air pressure will decrease. If the air at the bottom of this column is cooled, it will sink, and the air pressure will increase.

14.) Explain why , on a map, closely spaced isobars (or contours) indicate strong winds, and widely spaced isobars (or contours) indicate weak winds.

Isobars are lines drawn on a weather map that connect points of equal pressure around low (L) and high (H) pressure areas. The spacing between the isobars indicates the steepness of the pressure gradient between the low and the high pressure area. The closer the isobars, the steeper the pressure gradient. Closely spaced isobars indicate a steep pressure gradient and high winds whereas widely spaced isobars indicate a gentle pressure gradient and weak winds.

13.) What is the name of the force that initially sets the air in motion and , hence, causes the wind to blow?

Pressure gradient forces. Unequal heating of the air results in differences in air pressure. Differences in air pressure develop pressure gradient forces, and it is these forces that cause the wind to blow. Because of this fact, closely spaced isobars on a weather map indicate steep pressure gradients, strong forces, and high winds.

20.) Describe how the wind blows around high-pressure areas and low-pressure areas aloft and near the surface (a) in the Northern Hemisphere; and (b) in the Southern Hemisphere.

The Coriolis force deflects moving air to the right in the northern hemisphere, and to the left in the southern hemisphere. As a result, the flow around high and low pressure differs in the two hemispheres. (a) In the northern hemisphere, winds blow counterclockwise around a low pressure are and clockwise around a high pressure area. (b) In the southern hemisphere, winds blow clockwise around a low pressure are and counterclockwise around a high pressure area. Thus, the northern hemisphere's wind flow is opposite of the southern hemisphere's wind flow.

TE-5.) Explain why, on a sunny day, an aneroid barometer would indicate "stormy" weather when carried to the top of a hill or mountain.

An aneroid barometer is a type of barometer that measures air pressure mechanically with springs and levers. The face of an aneroid barometer often has weather related words printed above specific pressure values. A general rule of thumb regarding air pressure and weather is that low pressure = cloudy, stormy weather. If an aneroid barometer is carried to the top of a mountain on a bright, sunny day, it will indicate low pressure indicating bad weather. The barometer misreads the weather because air pressure decreases as you go upward. To account for this, aneroid barometers used by the weather service are calibrated to the altitude at which they are kept.