Visualizing Physical Geography Chapter 5

Front 1

Define atmospheric pressure.

Back 1

Pressure exerted by the atmosphere because of the force of gravity acting upon the overlying column of air.

Front 2

What causes atmospheric pressure?

Back 2

Atmospheric pressure is caused by the weight of a column of air above the Earth's surface forcing pressure on that area of the Earth's surface.

Front 3

How does atmospheric pressure change with altitude?

Back 3

Air pressure decreases with altitude because there is less air weighing down at higher altitudes.

Front 4

Describe how pressure grandients drive wind.

Back 4

Air tends to move from regions of high pressure to regions of low pressure, until the pressure at every level is uniform. Air moves along the pressure gradient to make everything equal

Front 5

Discuss local wind systems.

Back 5

Local wind systems are wind systems generated by local effects.

Front 6

Explain convection loops.

Back 6

Convection loops occur when an area above the Earth is heated more than another area. The air above the warmer area rises, creating lower pressure near the Earth and higher pressure at a higher altitude. The air at higher pressure at the higher altitude moves to areas of lower pressure. At this area the air descends over the cooler area and creates a higher pressure near the Earth. That air then moves towards the area of lower pressure above the warmer area, completeing the loop. (See graphic 1)

Front 7

What is a pressure gradient?

Back 7

A pressure gradient is a change of atmospheric pressure measured along a line at right angles to the isobars.

Front 8

How do pressure gradients drive local wind patterns?

Back 8

Air tends to move from regions of high pressure to regions of low pressure, until the pressure at every level is uniform. Air moves along the pressure gradient to make everything equal

Front 9

How do convection loops develop?

Back 9

Convection loops develop when there is unequal heating of a fluid.

Front 10

What are two examples of local winds?

Back 10

Valley breezes and sea land breezes

Front 11

Explain the Coriolis effect.

Back 11

Effect of the Earth's rotation that acts like a force to deflect a movin object on the Earth's suface to the right in the northern hemisphere and to the left in the southern hemisphere.

Front 12

Discuss cyclones and anticyclones

Back 12

Cyclones are areas of low atmospheric pressure where air spirals inward and upward. Anticyclones are centers of high atmospheric pressure where air spirals downward and outward. In the northern hemisphere, cyclones inspiral counterclockwise and anticyclones outspiral clockwise. The direction is opposite in the southern hemisphere.

Front 13

What causes the Coriolis effect?

Back 13

Effect of the Earth's rotation that acts like a force to deflect a movin object on the Earth's suface to the right in the northern hemisphere and to the left in the southern hemisphere.

Front 14

How does the Coriolis force deflect the paths of moving objects?

Back 14

The Coriolis force appears to deflect the paths of moving objects because it makes them deflect them to the right in the northern hemisphere and left in the southern hemisphere. This occurs regardless of the direction of motion.

Front 15

How do cyclones and anticyclones develop?

Front 16

Define Hadley cells and explain how they affect wind patterns

Back 16

Hadley cell is a low latitude atmospheric circulation cell with rising air over the equatorial trough and sinking air over the subtropical high pressure belts (approx 30 degrees). As the air moves poleward, the Coriolis force turns it to the right.

Front 17

Discuss the intertropical convergence zone (ITCZ) and the subtropical high-pressure belts

Back 17

The ITCZ is a zone created when air from both hemispheres moves towards the equatorial trough. The ITCZ is where that air converges. There are two subtropical high pressure belts, each at about 30 degrees latitude. They are the area that air descends on the poleward side of the Hadley cell, so there surface pressures are high.

Front 18

Describe monsoon circulation.

Back 18

Monsoons are a result of subtropical high-pressure zones moving through the seasons

Front 19

Explain the differences between pressure patterns in the northern and southern hemispheres.

Back 19

The pressure patterns in the southern hemishpere are different because there is a massive anticyclone always present over Antartica. Surrounding the high is a band of deep low pressure, with strong, indward- spiraling westerly winds.

Front 20

How do Hadley cells develop?

Back 20

Hadley cells develop when the area above the equator is heated more than areas at higher latitudes. This creates a convection loop above the equator to about 30 degrees latitude.

Front 21

Explain how pressure gradients develop at upper levels.

Back 21

Pressure gradients develop at upper levels similar to how they do at the surface.

Front 22

Explain how Rossby waves develop and grow.

Back 22

Front 23

Where do Rosssby waves develop?

Back 23

Rossby waves develop in polar fronts- the zone where cold polar air meets warm tropical air.

Front 24

Why are Rossby waves important?

Back 24

Rossby waves are the reason weather in the midlatitudes is often so variable, because they cause pools of warm, moist air and cold, dry air to alternately invade midlatitude land masses.

Front 25

Discuss geostophic wind.

Back 25

Geostrophic wind is wind at high levels above the Earth's surface blowing parallel with a system of straight, parallel isobars. Upper air does not have friction force because it is so far from the source of friction- the surface. So there are only two forces on teh air parcel- the pressure gradient force and the Coriolis force. As the parcel of air accelerates, the Coriolis ofce pulls it increasingly toward the right. as its velocity increases, the parcel turns increasinly rightward until the Coriolis force just balances the gradient force. At that point, the sum of the forces on the parcel is zero, so its speed and direction remain constant.

Front 26

Describe ocean currents and why they occur.

Back 26

An ocean current is a persistent, dominantly horizontal flow of water. Ocean currents occur because the Earth is constantly trying to create an engergy balance. The currents are driven by differences in density and pressur acting along with the Coriolis force.

Front 27

Explain the general features of global surface current patterns.

Back 27

In surface currents, energy is transferred from the prevailing surace wind to water by the friction of the air blowing over the water surface. Because of the Coriolis effect, the actual direction of water drift is deflected about 45 degrees from the direction of the driving wind.

Front 28

What is the basic metric unit of pressure?

Back 28

The pascal (Pa)

Front 29

How is wind direction identified?

Back 29

The direction from which the wind comes- a west wind blows from west to east, for example.

Front 30

Describe Valley breezes during the day.

Back 30

During the day, mountain hill slopes are heated intensely by the sun, making the air expand and rise, creating a valley breeze. An air current moves up valleys from the palins below- opward over rising mountain slopes, toward the summits.

Front 31

Describe Valley breezes during the night.

Back 31

At night, the hill slopes are chilled by radiation, setting up a reversed convection loop. The cooler, denser hill slope air moves valleyward, down the hill slopes, to the plain below.

Front 32

What effects the strength of the Coriolis effect?

Back 32

The Coriolis "force" increases with the speed of motion but decreases with latitude.

Front 33

What kind of weather are cyclones usually associated with? Why?

Back 33

Cyclones are usually associated with cloudy or rainy weather. This is because when air is forced upware, it is cooled according to the adiabatic princple, allowing condensation and precipitation to begin.

Front 34

What kind of weather are anticyclones usually associated with? Why?

Back 34

Anticyclones are usually associated with fair weather. This is because when air sinks it is warmed by the adiabtic process, so condensation can't occur.

Front 35

Isobars

Back 35

Lines on a map drawn through all points having the same atmospheric pressure

Front 36

Presure gradient

Back 36

Change of atmospheric pressure measured along a line at right angles to the isobars

Front 37

Convection loops

Back 37

Circuit of moving fluid, such as air or water, created by unequal heating of the fluid.

Front 38

Equitorial trough

Back 38

The zone created by rising air at the equator that has a low surface pressure.

Front 39

Convergence

Back 39

The inward spiraling motion found in cyclones.

Front 40

Divergence

Back 40

The outward spiraling motion found in anticyclones.

Front 41

trade winds

Back 41

Winds around the subtropical high pressure center that spiral outward and moves toward the equatorial as well as middle latitudes. They are dependable trade winds that drove the siling ships of merchant traders.

Front 42

Intertropical convergence zone (ITCZ)

Back 42

The ITCZ is a zone of convergence of air masses along the equatorial trough.

Front 43

Subtropical high-pressure belts

Back 43

Subtropical high-pressure belts are belts of persistent high atmospheric pressure centered at about lat. 30 degrees N and S.

Front 44

Jet streams

Back 44

High-speed air flow in narrow bands within the upper-air westerlies and along certain other global latitude zones at high levels

Front 45

Geostrophic wind

Back 45

Wind at high levels above the Earth's surface blowing parallel with a system of straight, parallel isobars.

Front 46

Polar front

Back 46

The zone where cold polar air meets warm tropical air.