Atmospheric Patterns of Motion

Question 1

What are the three categorize of Atmospheric circulation?

Answer 1

Atmospheric circulation is categorized at three levels: primary circulation, consisting of general worldwide circulation; secondary circulation, consisting of migratory high-pressure and low-pressure systems; and tertiary circulation, including local winds and temporal weather patterns.

Question 2

What are meridional/zonal flows?

Answer 2

Winds that move principally north or south along meridians of longitude are meridional flows. Winds moving east or west along parallels of latitude are zonal flows.

Question 3

How dose the warmer and colder air behave on the equator and poles?

Answer 3

The warmer, less-dense air along the equator rises, creating low pressure at the surface, and the colder, more-dense air at the poles sinks, creating high pressure at the surface.

Question 4

What would happen to wind flow if the earth didn’t rotate?

Answer 4

If Earth did not rotate, the result would be a simple wind flow from the poles to the equator, a meridional flow caused solely by pressure gradient. However, Earth does rotate, creating a more complex flow system.

Question 5

How is the pole-to-equator flow broken up on a rotating earth?

Answer 5

On a rotating Earth, the poles-to-equator flow is broken up into latitudinal zones, both at the surface and aloft in the upper-air winds.

Question 6

How do high and low pressure areas of earths primary circulation appear on maps?

Answer 6

The high- and low-pressure areas of Earth’s primary circulation appear on these maps as cells or uneven belts of similar pressure that are interrupted by landmasses. Between these areas flow the primary winds.

Question 7

Explain the formation of earth’s secondary circulation.

Answer 7

The highs and lows of Earth’s secondary circulation form within these primary pressure areas, ranging in size from a few hundred to a few thousand kilometres in diameter and hundreds to thousands of metres in height. The systems of secondary circulation seasonally migrate to produce changing weather patterns in the regions over which they pass.

Question 8

How many primary pressure areas cover the Northern/Southern Hemisphere? Of those, how many are stimulated by thermal (temperature) factors?

Answer 8

Four broad primary pressure areas cover the Northern Hemisphere, and a similar set exists in the Southern Hemisphere. In each hemisphere, two of the pressure areas are stimulated by thermal (temperature) factors.

Question 9

What are the two thermal areas in the northern/southern hemispheres that are stimulated by thermal factors called?

Answer 9

These are the equatorial low (marked by the ITCZ line on the maps) and the weak polar highs at the North and South Poles

Question 10

What is the Equatorial low

Answer 10

Equatorial low
A thermally caused low-pressure area that almost girdles Earth, with air converging and ascending all along its extent; also called the intertropical convergence zone (ITCZ).

Question 11

What is the Polar high?

Answer 11

Weak, anticyclonic, thermally produced pressure systems positioned roughly over each pole; that over the South Pole is the region of the lowest temperatures on Earth. (See Antarctic High.)

Question 12

How dose heat and cold affect air pressure?

Answer 12

Remember from our discussion of pressure, density, and temperature earlier in the chapter that warmer air is less dense and exerts less pressure. The warm, light air in the equatorial region is associated with low pressure, while the cold, dense air in the polar regions is associated with high pressure.

Question 13

What are the two pressure areas in each hemisphere that are formed by dynamic (mechanical) factors

Answer 13

The other two pressure areas—the subtropical highs (marked with an H on the map) and subpolar lows (marked with an L)—are formed by dynamic (mechanical) factors.

Question 14

What are the Subtropical highs?

Answer 14

One of several dynamic high-pressure areas covering roughly the region from 20° to 35° N and S latitudes; responsible for the hot, dry areas of Earth’s arid and semiarid deserts. (See Anticyclone.

Question 15

What are the Subtropical highs

Answer 15

One of several dynamic high-pressure areas covering roughly the region from 20° to 35° N and S latitudes; responsible for the hot, dry areas of Earth’s arid and semiarid deserts. (See Anticyclone.

Question 16

What kind of air patterns are associated with High and Low pressure?

Answer 16

Remember in our discussion of pressure gradients that converging, rising air is associated with low pressure, whereas subsiding, diverging air is associated with high pressure—these are dynamic factors because they result from the physical displacement of air.

Question 17

Cause Location Air Temperature/ Moisture of Polar High

Answer 17

Thermal 90° N, 90° S Cold/dry

Question 18

Cause Location Air Temperature/ Moisture of Subpolar low

Answer 18

Dynamic 60° N, 60° S Cool/w

Question 19

Cause Location Air Temperature/ Moisture of Subtropical High

Answer 19

Dynamic 20°–35° N, 20°–35° S Hot/dry

Question 20

Cause Location Air Temperature/ Moisture Equatorial low

Answer 20

Thermal 10° N to 10° S Warm/wet

Question 21

Describe the Equatorial Low or ITCZ

Answer 21

Also called Intertropical convergence zone (ITCZ)

Constant high Sun altitude and consistent daylength (12 hours a day, year-round) make large amounts of energy available in the equatorial region throughout the year. The warming associated with these energy surpluses creates lighter, less-dense, ascending air, with surface winds converging along the entire extent of the low-pressure trough. This converging air is extremely moist and full of latent heat energy. As the air rises, it expands and cools, producing condensation; consequently, rainfall is heavy throughout this zone (condensation and precipitation are discussed in Chapter 7). Vertical cloud columns frequently reach the tropopause, in thunderous strength and intensity.

Question 22

What is a characteristic that the equatorial low can be identified by?

Answer 22

The equatorial low, or equatorial trough, forms the intertropical convergence zone (ITCZ), which is identified by bands of clouds along the equator and is noted on

Question 23

What are the Trade Winds?

Answer 23

The winds converging at the equatorial low are known generally as the trade winds, or trades.

Winds from the northeast and southeast that converge in the equatorial low-pressure trough, forming the intertropical convergence zone.

Question 24

Where do the northeast and southeast trade winds blow?

Answer 24

Northeast trade winds blow in the Northern Hemisphere and southeast trade winds in the Southern Hemisphere.

Question 25

How were the trade winds named?

Answer 25

The trade winds were named during the era of sailing ships that carried merchandise for trade across the seas. These are the most consistent winds on Earth

Question 26

What are Hadley cells and how were they named?

Answer 26

Circulation cells, called Hadley cells, in each hemisphere that begin with winds rising along the ITCZ. These cells were named for the eighteenth-century English scientist who described the trade winds.

Question 27

How dose air move in the Hadley cells?

Answer 27

Within these cells, air moves northward and southward into the subtropics, descending to the surface and returning to the ITCZ as the trade winds. The symmetry of this circulation pattern in the two hemispheres is greatest near the equinoxes of each year.

Question 28

What are doldrums?

Answer 28

Within the ITCZ, winds are calm or mildly variable because of the weak pressure gradient and the vertical ascent of air. These equatorial calms are called the doldrums (from an older English word meaning “foolish”) because of the difficulty sailing ships encountered when attempting to move through this zone.

Question 29

How dose the rising air from the equatorial low pressure areas behave?

Answer 29

The rising air from the equatorial low-pressure area spirals upward into a geostrophic flow running north and south. These upper-air winds turn eastward, flowing from west to east, beginning at about 20° N and 20° S, and then descend into the high-pressure systems of the subtropical latitudes.

Question 30

Where are the subtropical highs located?

Answer 30

Between 20° and 35° latitude in both hemispheres, a broad high-pressure zone of hot, dry air brings clear, frequently cloudless skies over the Sahara and the Arabian Deserts and portions of the Indian Ocean

Question 31

Why are the subtropical highs typically dry?

Answer 31

These subtropical anticyclones generally form as air above the subtropics is mechanically pushed downward and heats by compression on its descent to the surface. Warmer air has a greater capacity to absorb water vapour than does cooler air, making this descending warm air relatively dry (discussed in Chapter 7). The air is also dry because moisture is removed as heavy precipitation along the equatorial portion of the circulation.

Question 32

What are the high pressure areas that are dominant in the subtropics of the northern hemisphere

Answer 32

Several high-pressure areas are dominant in the subtropics (Figure 6.10). In the Northern Hemisphere, the Atlantic subtropical high-pressure cell is the Bermuda High (in the western Atlantic) or the Azores High (when it migrates to the eastern Atlantic in winter).

Question 33

What is the Bermuda High?

Answer 33

Bermuda High

A subtropical high-pressure cell that forms in the western North Atlantic. (See Azores High.)

Question 34

What is the Azores High?

Answer 34

A subtropical high-pressure cell that forms in the Northern Hemisphere in the eastern Atlantic (See Bermuda High); associated with warm, clear water and large quantities of sargassum, or gulf weed, characteristic of the Sargasso Sea.

Question 35

What is the pacific/Hawaiian high?

Answer 35

A high-pressure cell that dominates the Pacific in July, retreating southward in the Northern Hemisphere in January; also known as the Hawaiian High.

The Pacific High, or Hawaiian High, dominates the Pacific in July, retreating southward in January.

Question 36

What are some characteristics of the subtropical pressure system in the Atlantic?

Answer 36

The entire high-pressure system migrates with the summer high Sun, fluctuating about 5°–10° in latitude. The eastern sides of these anticyclonic systems are drier and more stable (exhibit less convective activity) and are associated with cooler ocean currents. These drier eastern sides influence climate along subtropical and midlatitude west coast

Question 37

What dose the diverging surface area with in the subtropical high pressure cells generate?

Answer 37

Surface air diverging within the subtropical high-pressure cells generates Earth’s principal surface winds: the trade winds that flow toward the equator, and the westerlies, which are the dominant winds flowing from the subtropics toward higher latitudes.

Question 38

What are some characteristics of The Westerlies?

Answer 38

The westerlies diminish somewhat in summer and are stronger in winter in both hemispheres. These winds are less consistent than the trade winds, with variability resulting from midlatitude migratory pressure systems and topographic barriers that can change wind direction.

Question 39

What are two low pressure cyclonic cells that exist over the oceans around 60° N latitude

Answer 39

In January, two low-pressure cyclonic cells exist over the oceans around 60° N latitude, near their namesake islands: the North Pacific Aleutian Low and the North Atlantic Icelandic Low (see Figure 6.10a). Both cells are dominant in winter and weaken or disappear in summer with the strengthening of high-pressure systems in the subtropics.

Question 40

What is the polar front?

Answer 40

A significant zone of contrast between cold and warm air masses; roughly situated between 50° and 60° N and S latitude.

The area of contrast between cold air from higher latitudes and warm air from lower latitudes forms the polar front, where masses of air with different characteristics meet

Question 41

What happens when the warm moist air from the westerlies meets the cold dry air from the polar and arctic regions?

Answer 41

Polar front - where warm, moist air from the westerlies meets cold, dry air from the polar and Arctic regions. Warm air is displaced upward above the cool air at this front, leading to condensation and precipitation

Question 42

What effect does the low-pressure cyclonic storms that migrate out of the Aleutian and Icelandic frontal areas have?

Answer 42

Low-pressure cyclonic storms migrate out of the Aleutian and Icelandic frontal areas and may produce precipitation in North America and Europe, respectively. Northwestern sections of North America and Europe generally are cool and moist as a result of the passage of these cyclonic systems onshore—consider the weather in British Columbia, Washington, Oregon, Ireland, and the United Kingdom.

Question 43

What are some characteristics of the polar high-pressure cells.

Answer 43

Polar high-pressure cells are weak. The polar atmospheric mass is small, receiving little energy from the Sun to put it into motion. Variable winds, cold and dry, move away from the polar region in an anticyclonic direction. They descend and diverge clockwise in the Northern Hemisphere (counterclockwise in the Southern Hemisphere) and form weak, variable winds of the polar easterlies

Question 44

What are the Polar Easterlies?

Answer 44

Variable, weak, cold, and dry winds moving away from the polar region; an anticyclonic circulation.

Question 45

Which of the two polar regions has the stronger and more persistent high-pressure system?

Answer 45

Of the two polar regions, the Antarctic has the stronger and more persistent high-pressure system, the Antarctic High, forming over the Antarctic landmass.

Question 46

What is the Antarctic High

Answer 46

Antarctic High
A consistent high-pressure region centered over Antarctica; the source region for an intense polar air mass that is dry and associated with the lowest temperatures on Earth.

Question 47

What are some characteristics of the high-pressure cell over the artic ocean?

Answer 47

Less pronounced is a polar high-pressure cell over the Arctic Ocean. When it does form, it tends to locate over the colder northern continental areas in winter (Canadian and Siberian Highs) rather than directly over the relatively warmer Arctic Ocean.