AP Environmental Science 4.5 - Global Wind Patterns

Summary

In this educational video, Mr. Smith explores Global Wind Patterns, explaining how the Earth's rotation, the Sun's energy, and air properties like density and moisture content influence atmospheric circulation. He delves into the Hadley cell, illustrating how warm air rises at the equator, cools, and precipitates, while also discussing the Coriolis effect's impact on wind direction. The video aims to help viewers understand the environmental factors behind these global weather patterns, using visual models to clarify complex concepts.

Takeaways

• 🌍 The Earth's rotation and the basic properties of air, such as density, are fundamental to understanding global wind patterns.
• 🌞 The intensity of the Sun's energy at the equator causes warm air to rise, leading to the formation of the Hadley cell, which is a key component of global wind patterns.
• 🔥 Warm air is less dense than cold air and holds less moisture, which is why it rises and leads to precipitation as it cools and expands.
• 🌧️ Precipitation forms when the water vapor in rising warm air condenses due to cooling, which is a significant part of the atmospheric circulation process.
• 🔄 The Hadley cell is a circulation pattern between 0 and 30 degrees latitude, responsible for global wind patterns and the distribution of deserts and rainforests.
• 🏜️ Deserts typically form around 30 degrees north and south latitude due to the sinking of dry air, creating high-pressure systems.
• 📉 Air pressure differences cause air to move from high-pressure areas near 30 degrees towards low-pressure areas at the equator and 60 degrees.
• 🌀 The Coriolis effect, caused by Earth's rotation, deflects the path of winds and other moving objects, influencing wind direction and ocean currents.
• 🌬️ The trade winds between 0 and 30 degrees blow from east to west due to the Coriolis effect, impacting weather patterns and ocean circulation.
• 🌪️ Between 30 and 60 degrees, the westerlies blow from west to east, influenced by the Earth's faster rotation at lower latitudes.
• 📚 Understanding the relationships between the Sun's energy, air properties, and the Coriolis effect is essential for explaining global atmospheric circulation and weather patterns.

Q & A

What are the three basic factors that influence atmospheric circulation?

The three basic factors that influence atmospheric circulation are the intensity of energy from the Sun, properties of air such as density, and the spinning of the Earth on its axis, which produces the Coriolis effect.

Why does warm air rise and how does it affect weather patterns?

Warm air rises because it is less dense than cold air. As warm air rises, it cools and expands, leading to the condensation of water vapor into liquid, which forms precipitation such as rain or snow. This process affects weather patterns by causing precipitation in certain areas.

What is the Hadley cell and how does it influence global wind patterns?

The Hadley cell is a cycle of air circulation between 0 and 30 degrees latitude. Warm air rises at the equator, cools and spreads out, then sinks back down at 30 degrees north and south. This cycle influences global wind patterns by creating predictable wind and weather patterns, such as trade winds and desert formations at 30 degrees.

How does the Sun's energy impact air circulation at the equator?

Sunlight is most direct at the equator, causing air to warm and rise. As the warm air rises, it cools and expands, leading to condensation of water vapor into rain. This results in intense rainfall at the equator.

Why do deserts typically form around 30 degrees north and south latitude?

Deserts form around 30 degrees north and south latitude because the air that descends back to Earth at these latitudes is very dry. The cool, dry air creates high-pressure areas, leading to arid conditions and desert formation.

What causes air to move from high-pressure to low-pressure areas on Earth’s surface?

Air moves from high-pressure to low-pressure areas due to the pressure gradient force. At 30 degrees, the high-pressure system causes air to flow towards the low-pressure system at the equator and towards 60 degrees latitude, creating wind patterns.

How does the Earth's rotation affect wind patterns?

The Earth's rotation causes the Coriolis effect, which deflects the path of moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deflection results in curved wind patterns instead of straight north-south movement.

What is the Coriolis effect and how can it be understood using a baseball example?

The Coriolis effect is the deflection of moving objects, like wind, due to Earth's rotation. If you throw a baseball straight south from the North Pole, it will be deflected to the right because the ground beneath it is rotating. Similarly, wind is deflected as it moves across Earth's surface.

Why does wind between 30 and 60 degrees latitude move from west to east?

Wind between 30 and 60 degrees latitude moves from west to east because the Earth at 30 degrees is spinning faster than at 60 degrees. This difference in rotational speed causes the wind to be deflected in the same direction as Earth's spin, resulting in westerlies.

How do global wind patterns influence ocean currents?

Global wind patterns drive the circulation of ocean currents. In the Northern Hemisphere, winds create clockwise ocean currents, while in the Southern Hemisphere, they create counterclockwise currents. This movement of water affects climate and weather patterns globally.

Outlines

00:00

🌍 Introduction to Global Wind Patterns

Mr. Smith introduces the topic of global wind patterns, explaining that the session will cover the basic properties of air and the Earth's rotation, which are crucial for understanding atmospheric circulation and weather patterns. The objectives include explaining environmental factors that result in atmospheric circulation, focusing on the intensity of solar energy, air properties like density, and the Coriolis effect caused by Earth's rotation.

05:01

🌡️ Understanding Air Density and Moisture

The first factor influencing atmospheric circulation is air density. Warm air is less dense than cold air, causing it to rise. This concept is illustrated by the temperature difference between an attic and a basement in summer. Additionally, warm air holds less moisture than cold air, leading to dry winter skin. As warm air rises and cools, it expands, and the water vapor condenses into precipitation, which falls back to Earth. This rising and cooling process is part of the Hadley cell, explaining global wind patterns between 0 and 30 degrees latitude.

☀️ The Sun's Role in Atmospheric Circulation

The second factor is the energy from the Sun. Direct sunlight at the equator warms the air, causing it to rise, cool, and expand, leading to intense rainfall. This cycle contributes to predictable weather patterns, such as deserts at 30 degrees latitude where cool, dry air descends. The high pressure at 30 degrees and low pressure at the equator cause air to move along the Earth's surface back towards the equator, completing the Hadley cell cycle.

🌪️ The Coriolis Effect and Wind Direction

The third factor is Earth's rotation, which causes the Coriolis effect. Objects moving through the atmosphere are deflected due to the Earth's spin. For instance, a baseball thrown southward from the North Pole is deflected to the left. Similarly, wind between 0 and 30 degrees is deflected from east to west. Wind from 30 to 60 degrees moves in the same direction as Earth's spin, due to the varying speeds of Earth's rotation at different latitudes. This concept is illustrated using the analogy of switching between treadmills moving at different speeds.

🌀 Combining Factors for Global Wind Patterns

Combining solar energy, air properties, and the Coriolis effect reveals Earth's global wind patterns. The Hadley cell demonstrates air rising at the equator, sinking at 30 degrees, and moving back towards the equator and 60 degrees. The deflection caused by Earth's rotation results in Eastern trade winds and westerlies, influencing ocean currents and weather patterns. In North America, weather moves from west to east due to westerlies, affecting how weather forecasts are interpreted. The session concludes with a practice question on the Sun's role in air circulation patterns.

Keywords

💡Global Wind Patterns

Global wind patterns refer to the large-scale movements of air around the Earth. They are crucial in understanding weather systems and climate. In the video, Mr. Smith discusses how these patterns are influenced by the Earth's rotation, the intensity of solar energy, and the properties of air, such as density and temperature. The concept is central to the video's theme, as it underpins the explanation of atmospheric circulation and weather patterns.

💡Atmospheric Circulation

Atmospheric circulation is the large-scale movement of air that distributes heat and moisture around the Earth. It is defined by the movement of air masses and is a key concept in the video. Mr. Smith explains how atmospheric circulation is driven by the intensity of solar energy, the properties of air, and the Coriolis effect, which together create the global wind patterns.

💡Coriolis Effect

The Coriolis effect is the apparent deflection of the path of an object that is moving in a rotating system. In the context of the video, it is responsible for the deflection of wind patterns, causing them to move east-west between 30 degrees latitude north and south, rather than moving directly north-south. This effect is essential in shaping global wind patterns and is a fundamental part of the Earth's weather systems.

💡Hadley Cell

The Hadley cell is a circulation pattern of air that moves between the equator and 30 degrees latitude north and south. It is named after George Hadley and is a primary driver of global wind patterns. In the script, Mr. Smith describes the Hadley cell as a cycle of air circulation that is largely responsible for the Earth's wind patterns, with warm air rising at the equator and sinking at 30 degrees latitude, creating high and low-pressure systems.

💡Solar Energy

Solar energy is the radiant energy emitted by the Sun, which is the primary source of energy for the Earth's weather and climate systems. In the video, solar energy is identified as a key factor in atmospheric circulation, as it heats the air at the equator, causing it to rise and initiate the Hadley cell circulation. The intensity of solar energy is directly related to the formation of wind patterns and weather systems.

💡Air Density

Air density refers to the mass of air per unit volume. In the video, Mr. Smith explains that warm air is less dense than cold air, which is why it rises. This property of air is fundamental to understanding atmospheric circulation, as it explains why warm air at the equator rises and creates areas of low pressure, while cooler, denser air at higher latitudes sinks, creating high-pressure areas.

💡Moisture Content

Moisture content in air refers to the amount of water vapor present. The video script mentions that warm air holds less moisture than cold air, which is why cold winter air feels drier. This concept is important for understanding precipitation patterns, as the rising warm air cools and expands, leading to the condensation of water vapor into clouds and eventually precipitation.

💡Precipitation

Precipitation is any form of water that falls from the atmosphere, such as rain, snow, sleet, or hail. In the video, Mr. Smith discusses how the condensation of water vapor in rising air leads to precipitation. This process is a key part of the Hadley cell circulation, where warm air rises, cools, and releases moisture as rain at the equator.

💡Deserts

Deserts are regions characterized by very low precipitation and typically occur in subtropical areas, such as around 30 degrees latitude north and south. In the script, Mr. Smith explains that the sinking of cool, dry air at these latitudes creates high-pressure systems, which result in the formation of deserts due to the lack of moisture.

💡Pressure Systems

Pressure systems refer to areas of the Earth's atmosphere where air pressure is consistently higher or lower than the surrounding areas. High-pressure systems, as mentioned in the video, are associated with sinking air and clear weather, while low-pressure systems are associated with rising air and precipitation. The video explains how these pressure systems, particularly at the equator and 30 degrees latitude, influence global wind patterns.

💡Trade Winds

Trade winds are the easterly winds that blow from the subtropical high-pressure zones toward the equatorial low-pressure zone. In the video, Mr. Smith describes how the trade winds are part of the global wind patterns and are influenced by the Coriolis effect, which deflects the winds to blow from east to west between the equator and 30 degrees latitude.

Highlights

Introduction to topic 4.5 on global wind patterns and their relation to atmospheric circulation.

Explanation of environmental factors affecting atmospheric circulation, including solar energy, air properties, and the Coriolis effect.

The concept that warm air is less dense than cold air, leading to its rise and the formation of weather patterns.

Warm air holds less moisture than cold air, which influences humidity and precipitation.

The process of warm air rising, cooling, expanding, and eventually condensing to form precipitation.

Description of the Hadley cell, a major air circulation pattern between 0 and 30 degrees latitude.

The role of solar energy in warming equatorial air and initiating the Hadley cell cycle.

How the condensation of water vapor in rising air leads to intense rainfall at the equator.

The formation of deserts around 30 degrees latitude due to descending dry air.

The movement of air from high to low pressure systems and its significance in the Hadley cell.

The impact of Earth's rotation on wind direction, introducing the Coriolis effect.

Illustration of the Coriolis effect using the analogy of throwing a baseball at the North Pole.

Explanation of how the Coriolis effect deflects wind direction in the Northern and Southern Hemispheres.

The concept of wind moving from east to west between 30 and 0 degrees due to the Coriolis effect.

The role of Earth's rotation speed in deflecting wind direction from west to east between 30 and 60 degrees.

The practical application of understanding wind patterns in predicting weather and ocean currents.

The integration of solar energy, air properties, and the Coriolis effect in shaping Earth's global wind patterns.

The significance of the Eastern trade winds in historical maritime trade and ocean current circulation.

The westerlies' influence on weather patterns in North America, with weather systems moving from west to east.

Encouragement to practice explaining relationships between environmental concepts using visual models.

Transcripts

everybody its mr. Smith and today we'll

be talking about topic 4.5 which is

global wind patterns so we'll be

learning how the basic properties of air

as well as how the rotation of earth

give us the wind patterns that we see on

earth and how they're also responsible

for the weather patterns that we see our

objective for the day is to be able to

explain environmental factors that

result in atmospheric circulation and in

order to do that we need to understand

three basic factors those are the

intensity of energy from the Sun

properties of air such as density and

the spinning of the earth on its axis

which produces something known as the

Coriolis effect our suggested science

skill to practice today is explaining

relationships between characteristics of

environmental concepts or models that

are presented visually so as I mentioned

the first factor that determines

atmospheric circulation is how airs

density changes under different

conditions so the first property of air

related to its density is that warm air

is less dense than cold air so it rises

if you've ever been in a house with an

attic in the summer the difference in

temperature between the attic and the

basement is a really great example of

this property we also need to understand

that warm air holds less moisture than

cold air so think about how dry and

cracked your skin gets in the winter

versus summer

that's because cold winter air holds

less moisture now another factor we need

to understand is that as warm air rises

it cools and that causes it to expand

and because cold air can't hold as much

moisture the water vapor that's in warm

rising air will condense into liquid

which forms precipitation in the

atmosphere and that eventually falls

down to earth as rain or snow or sleet

and finally after air has risen cooled

and expanded it's spread out and then

eventually it sinks back down and we'll

see that happen here in the diagram at

30 degrees north and south so these

properties of air help us understand the

diagram to the left here which is called

a Hadley cell the Hadley cell is this

cycle of air circulation between 0

degrees and 30 degrees and it's largely

responsible for our global wind patterns

on earth so now that we have our basic

properties of air down which is the

first factor influencing atmospheric

circulation now we're going to introduce

second factor which is energy from the

Sun so because sunlight is most direct

at the equator that's going to cause air

here to warm and rise so we can see that

as step one in the diagram as warm air

rises it cools and expands and because

cool air holds less moisture than warm

air the water vapor has to condense into

rain and so if we look at step two in

the diagram that's why we see such

intense rain at the equator because that

warm rising air has its water vapor

condensed and then fall down to earth is

rain in step three the air continues to

rise cool and expand further in step

four this air is expanding and spreading

out even further and then in Step five

we have cool dry air is sinking back

down to earth right around 30 degrees

north and south and as we can see in the

diagram this is going to explain why we

see this predictable pattern of deserts

forming all over the earth around 30

degrees north and south it's because the

air that's descending back down to earth

here is incredibly dry so we get deserts

however we're not quite done

understanding the Hadley cell if we look

at the diagram we'll see that we have

this arrow here that's going from 30

degrees back towards the equator so why

is air moving along Earth's surface from

30 degrees back to the equator well we

have high pressure at 30 degrees north

and south that's because we have this

column of cool dry air that's sinking

back down to earth and when a column of

air is pushing down on earth it gives us

high pressure meanwhile at the equator

we have low pressure and that's because

warm air being heated from the Sun is

rising at the equator and we know that

air moves from high to low pressure

so along Earth's surface we'll see this

air from 30 degrees flowing back towards

the equator that's because we're moving

from high to low pressure another way to

think about this though is we have to

get back to step one of the cycle

somehow and so we need replacement air

to come in and fill this vacuum or this

gap of air left by the air that's rising

at the beginning of the Hadley cell so

we've covered why air rises and expands

at the equator sinks back down at 30

degrees and then moves along Earth's

surface back towards

the equator but that's only two of the

three factors that determine atmospheric

circulation the third factor is Earth's

rotation so believe it or not if earth

were standing still rather than spinning

wind would move more or less just

straight north and south because the

earth is rotating though that means that

objects such as wind or this baseball

we'll talk about here in a second that

our traveling through Earth's atmosphere

are actually deflected in the opposite

direction of Earth's rotation so another

way to try to understand the Coriolis

effect is to imagine that you're

standing at the North Pole and you're

throwing a baseball straight south so

you may be aiming the baseball along

this line here

but because Earth's rotation is causing

the ground beneath the baseball to spin

the baseball will actually be deflected

the opposite direction of the spin so

even though the ball was traveling on

this trajectory it's going to end up

here to the left of where you aimed it

because the ground beneath the earth is

spinning now the same thing is true of

the wind between 0 and 30 degrees so

because this air at 30 degrees is moving

from a high pressure system back down to

a low pressure system it would flow

directly south are directly north in the

southern hemisphere but because earth is

spinning this direction the wind from 0

from 30 to 0 degrees is deflected the

opposite direction so what we get is

wind moving from east to west between 30

and 0 degrees now because 30 degrees is

a higher pressure area than 60 degrees

wind is also moving from 30 degrees out

to 60 degrees the wind in this direction

though is deflected in the opposite

direction as between 30 and 0 and that's

because the earth at 30 degrees is

spinning so much faster than it is at

higher latitudes at 80 or even at 60

that the wind is actually going to be

deflected in the same direction as

Earth's spin now that's a confusing

concept so let's talk about this using

the example of a treadmill imagine that

you're running along a treadmill that's

going 15 miles an hour and suddenly

you've jumped to a treadmill right next

to you moving in the same direction but

only

moving two miles an hour so it's moving

far more slowly you're going to have so

much momentum coming from the 15 mile an

hour treadmill that jumping onto the 2

mile an hour treadmill is going to cause

you to run forward quite a bit and so

that's why we see wind from 30 degrees

to 60 degrees actually traveling in the

same direction as Earth's spin it's

because the earth is spinning so much

faster at 30 degrees than 60 degrees

that the wind is deflected in that

direction of our spin now we'll put

together all three factors so the sun's

energy air properties like density and

the Coriolis effect to take a look at

how Earth's global wind patterns are the

result of those factors so the first

thing I want to do here is point out

that our Hadley cell here still works

the same way we're just looking at it

from a side view where we see all of

Earth rather than looking at it from the

viewpoint of being on Earth's surface

like we did in our first slide so if we

look at the Hadley cell we can remember

that the sun's rays are striking the

equator most directly so that's heating

the air here and causing it to rise then

it sinks back down at 30 degrees and

because of this high pressure system at

30 degrees air is going to be moving out

towards 0 degrees and 60 degrees we can

see here that with our low pressure at

the equator our higher pressure at 30

degrees and then our low pressure again

at 60 we're going to get air moving out

from 30 degrees towards 60 and towards

the equator but remember that the air

does not move in a straight line it's

deflected based on the direction of

Earth's spin and so between 0 and 30

degrees we have our air moving from east

to west and we call those Eastern trade

winds because they used to drive trade

from the east to the west because the

ships are dependent on sails this also

drives the circulation of the ocean

currents in a clockwise direction in the

northern hemisphere and in a

counterclockwise direction in the

southern hemisphere then remember that

between 30 and 60 degrees the wind is

blowing from west over to the east and

this is because the earth at 30 degrees

is moving so much faster than out at 60

degrees or 80 degrees that the wind is

deflected in that same direction as the

spin so it moves from west to east now

this means that in North America where

we live we get our weather from the West

so if you're looking at the radar to try

to see if we're going to have a snow day

you're gonna look over at Chicago and

Wisconsin because you know that their

storms are headed our direction because

we have westerlies or western prevailing

winds which means our weather moves from

the western United States over to the

eastern United States our suggested

science Gale for practice up for cue 4.5

today is explaining relationships

between characteristics of environmental

concepts or models that are represented

visually so I want you to see if you can

explain how is the Sun responsible for

the pattern of air circulation that we

see in cycles see on the diagram here

alright everybody thanks for tuning in

today don't forget to like this video if

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over here to the side and as always

think like a mountain write like a

scholar