5.2 Atmospheric Circulation

If a parcel of air is moving from 0° to 30°S, to which direction will it be deflected? What if it’s moving from 30°S to 0°?

0° to 30°S: To the east (making it southeast). 30°S to 0°: To the west (making it northwest)

If a parcel of air is moving from 30°N to 60°N, to which direction will it be deflected? What if it’s moving from 30°S to 60°S?

30°N to 60°N: To the east (making it northeast). 30°S to 60°S: To the east (making it southeast)

If a parcel of air is moving from 30°N to 0°, to which direction will it be deflected? What if it’s moving from 90°N to 60°N?

30°N to 0°: To the west (making it southwest). 90°N to 60°N: To the west (making it southwest)

Which way do winds rotate around a high-pressure zone in the southern hemisphere? What about in the northern hemisphere?

S Hemi: counterclockwise. N Hemi: clockwise

Which way do winds rotate around a low-pressure zone in the southern hemisphere? What about in the northern hemisphere?

S Hemi: clockwise. N Hemi: counterclockwise.

What is cyclonic flow? Which way does cyclonic flow rotate in the northern and southern hemispheres?

Def: air flow around a low pressure zone where air is rising. N Hemi: counterclockwise. S Hemi: clockwise

What is anticyclonic flow? Which way does anticyclonic flow rotate in the northern and southern hemispheres?

Def: air flow around a high pressure zone where air is sinking/falling. N Hemi: clockwise. S Hemi: counterclockwise

Which way does a hurricane in the northern hemisphere rotate? Is this a cyclone or an anticyclone? Why is this ocean important to the formation of hurricanes?

Hurricanes are low-pressure zones and rotate counterclockwise in the Northern Hemisphere. Hurricanes are cyclones. They can only form over warm ocean water because the water's heat causes evaporation, which creates moisture in the air, which then rises, creating low pressure (the ocean fuels the storm).

In summer in the northern hemisphere, what kind of large scale pressure zone would develop over the North Atlantic Ocean at this time? How would this affect the air temp along the US east coast?

During this time, the sun is directed toward the Northern Hemisphere. The land has a low specific heat capacity, so it heats up rapidly. The air above the land is heated, lowering its density and making it rise, creating a low-pressure zone. Due to its high heat capacity, the ocean's temperature stays relatively constant, creating high pressure as the air over the land rises and eventually falls over the water. Because the zone over the North Atlantic is high-pressure, the winds rotate clockwise. This brings hot, humid air to the US East Coast.

Name and state the direction of flow of the winds in each area: 60°N to 90°N, 60°N to 30°N, and 30°N to 0.

60°N to 90°N: Easterlies (blow east to west). 60°N to 30°N: Westerlies (blow west to east/southwest to northeast). 30°N to 0°: NE (northeast) Trade Winds (blow northeast to southwest).

Name and state the direction of flow of the winds in each area: 60°S to 90°S, 60°S to 30°S, and 30°S to 0°.

60°S to 90°S: Easterlies (blow southeast to northwest). 60°S to 30°S: Westerlies (blow northwest to southeast). 30°S to 0°: SE (southeast) Trade Winds (blow southeast to northwest)

Why does air rise at the equator? What type of pressure zone does this create?

The Sun hits the Earth most directly at the equator. This heats the land and water along the equator, creating hot, humid air (which decreases its density and makes it rise). A low pressure zone is created where air is rising.

Why does the air fall at 90°N and 90°S? What type of pressure zone does this create?

Because the Sun isn’t directed at the poles, the amount of the Sun’s energy hitting there is spread out and most is deflected by ice (the air there is very cold). Cold air is very dense, so it sinks and creates a high pressure zone.

How do the temperature and weather differ between 30° and 60°? What pressure zones exist at these latitudes?

The air is much warmer at 30° than at 60°. There is a high pressure zone at 30° and a low pressure zone at 60°. It’s generally dry at 30° and rainy at 60°.

Why do coastal areas often experience winds blowing from the ocean toward land in the afternoon/early evening?

This is due to the difference in specific heat capacity between land and water. Over the course of the day, the land heats up and creates a small scale low pressure zone. This air rises, then falls over the water, creating a high pressure zone over water and low pressure zone over land. Air will always move from high to low pressure. So, the air will come from water and blow to the land at the end of the day.

If air is cooled, does it get more or less dense?

More dense.

If the water at the ocean’s surface evaporates, does this make the air above it more or less dense? Would the air stay where it is, sink, or rise?

The evaporated water is added to the air (rising), becoming less dense.

How does the temperature in the troposphere change as you go from Earth’s surface to the tropopause?

It decreases.

Which part of Earth is heated the most? Which part is heated the least?

The equator is heated most (concentrated sun rays). The poles are heated the least (sun rays spread the most).

Does air rise or fall in a low pressure zone?

It rises.

What causes air to rise or fall?

Changes in density cause air to rise or fall. Cooled, dried air makes air more dense. Warmed, wetter air makes air less dense.

Is the equator a low or high pressure zone? What causes this?

It’s a low-pressure zone. Since the sun hits the equator directly, the air is warm and less dense. Water also evaporates and is added to the air. Warm, moist air rises, creating a low-pressure zone.

Are the poles low or high pressure? Why?

They’re high-pressure zones. Since the sun is spread thin in those areas, the air is cold, dry, and dense. This sinking air creates high-pressure zones.

Does air rise or fall at 30°N and S?

Falls

Does air rise or fall at 60°N and S?

Rises

Does air rise or fall at 90°N and S?

Falls

What happens to the temperature as you go up (in altitude) in the troposphere?

It decreases as you go up.

In which season is the southern hemisphere when the northern hemisphere is in Summer? Why?

It’s winter because the angle of the sun causes the seasons. The N Hemi experiences summer when the sun is hitting it most directly and the S Hemi is angled away from the sun.

Which direction would a parcel of air be deflected if traveling from 30°S to 60°S? Give an example.

It’d be deflected left of its intended direction because it’s in the S Hemi. If the intended direction is South, to the left would be East. Don’t forget to turn your paper so the arrow points up, draw the arrow to the left, then flip it back to normal to see the actual direction.

At which latitudes does air generally rise?

Air rises at the equator (0°), 60°N, and 60°S.

How are winds named?

Winds are named based on where they come from (not from where they’re going).

What is the name of the atmosphere where most of our weather occurs?

Troposphere

In which direction (up or down) does air move to create a high pressure zone?

Sinks/goes down

If a parcel of air is moving from 30 degrees N to 60 degrees N, which way would it be deflected?

East

If a parcel of air was moving from 60 degrees S to 30 degrees S, which way would it be deflected?

West