Download Part E: Chapter 18 Answers to Review Questions

Part E: Chapter 18 Answers to Review Questions
1. 1013 millibars; 29.92 inches of mercury; 14.7 pounds per square inch.
2. Standard sea level pressure equals 76 centimeters of mercury. Thus if a water barometer is
used standard sea level pressure will be measured as a column 13 times higher, or 988
centimeters of water.
3. An aneroid (without liquid) barometer consists of evacuated metal chambers that contract as
air pressure increases and expand when air pressure decreases.
4. The pressure gradient force causes winds to blow. Winds blow from regions of higher
pressure to regions of lower pressure; the bigger the pressure difference the greater the wind
speed.
5. Closely spaced isobars indicate a strong wind; widely spaced isobars indicate a light wind.
6. The Coriolis force (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. Upper-air winds generally parallel the isobars, because the pressure gradient force and the
Coriolis force balance each other. However, near Earth's surface, friction slows the winds.
Since the strength of the Coriolis force is proportional to the wind speed, the Coriolis force is
diminished. Consequently, the Coriolis force can no longer offset the pressure gradient force,
and the surface winds blow at an angle across the isobars.
8. A drop in barometric pressure indicates the approach of low pressure. Low pressure is associated with converging winds and ascending air; hence, it is often associated with clouds and
precipitation. Conversely, a rise in air pressure means the approach of high pressure with its
associated fair weather.
9. The diagram for the Southern Hemisphere should show winds blowing into and clockwise
around the low and out of and counterclockwise around the high. The diagrams for the Northern Hemisphere would show winds blowing into and counterclockwise around the low and
out of and clockwise around the high.
10. The winds west of a cyclone (Northern Hemisphere) would be northwest or west–northwest,
and winds west of an anticyclone would be south to southeast.
11. (a) subtropical highs
(b) westerlies and polar easterlies
(c) equatorial low
12. Upper-level air flow is responsible for directing the movement of pressure systems. There is a
close correlation between the paths taken by surface pressure systems and the position of
upper-level flow.
13. Monsoon circulation refers to a seasonal reversal of winds. In winter, the continent has a
large, thermally produced high. Thus winds blow off the continent (out of the high) toward
the ocean. This is generally a period of little, if any, precipitation. In summer, low pressure
forms over the land and moisture-laden winds blow from the ocean onto the land. The
summer is therefore the period of maximum rainfall.
14. Local winds are small-scale winds produced by a locally generated pressure gradient.
Examples of local winds include sea and land breezes, valley and mountain breezes, and
chinook and Santa Ana winds.
15. A northeast wind blows from the northeast toward the southwest.
16. During a major El Niño event, the barometric pressure drops over a large portion of the
southeastern Pacific, whereas in the western Pacific, near Indonesia and northern Australia,
the pressure rises. As a consequence, the once-steady trade winds diminish and may even
change direction. This wind reversal creates a major change in the equatorial current system,
with warm water flowing eastward.
17. Deserts such as the Sahara and Kalahari in Africa are associated with subtropical highs. The
tropical rainforests of the Amazon and Congo basins are associated with the equatorial low.
18. Other than Earth's pressure and wind belts, the (1) distribution of land and water and (2)
mountain barriers also influence the distribution of precipitation.
Answers to Earth System Questions
1. The region dominated by the equatorial low is both cloud covered and darker, which indicates
vegetation. Both conditions are the result of the moisture and precipitation associated with
low pressure. To the north and south of this region, clear skies and desert conditions with
sparse vegetation prevail beneath the subtropical highs.
2. Because surface ocean currents are set in motion by friction from the global winds, both
follow the same general circulation, clockwise in the Northern Hemisphere and
counterclockwise in the Southern Hemisphere.
The ultimate source of energy that drives both the atmospheric and oceanic circulation is the
Sun.
3. During an El Niño event, large quantities of warm water in the eastern Pacific cause an
uncommon abundance of rain in normally arid areas in Peru and Ecuador. These heavy rains
cause severe flooding and erosion. In addition, the warm pool of water blocks the upwelling
of colder, nutrient-filled water along the coast, and anchovies starve from lack of food,
devastating the local economies. Concurrently, severe drought can beset Indonesia, causing
huge crop losses, property damage, and much human suffering.