Climate and global circulation

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Apuntes de la lección

Unequal Heating and Latitude

The Sun's rays strike Earth's surface most directly at the Equator, making it warmer.
Near the poles, the Sun's rays are less direct and spread over a wider area, so temperatures are lower.
Latitude (distance north or south of the equator, measured in degrees) causes unequal heating of Earth's surface.
Places receiving more solar energy are warmer; places receiving less are cooler.
Warm air rises and cool air sinks, driving atmospheric circulation that redistributes heat.

The Sun's rays and latitude

Atmospheric Circulation

The atmosphere forms convection cells that move air from the equator toward the poles and back.
There are three main air cells in each hemisphere, averaging out the movement of air.
Atmospheric circulation brings warm air toward the poles and cold polar air toward the equator.
This movement moderates Earth's temperatures, balancing heat between warm and cold regions.
Global winds blow consistently in the same direction, influenced by unequal heating and Earth's rotation.

Global wind patterns showing westerlies and trade winds

Oceanic Circulation

Wind patterns push ocean water, creating surface currents that can flow for thousands of kilometers.
Surface currents distribute heat around the planet and are a major factor influencing climate.
The global conveyor belt describes the movement of warm water from the equator to the poles, where it cools, sinks, and returns.
The Gulf Stream is a warm ocean current that carries heat from the equator to Europe, raising temperatures and precipitation.
Ocean currents transfer heat from equatorial regions to higher latitudes, preventing extreme climate differences.

The global conveyor belt showing warm shallow currents and cold salty deep currents.

Temperature Inversions

A temperature inversion occurs when air temperature in the troposphere increases with altitude, with warm air sitting over cold air.
Inversions are stable and can last for days or weeks, trapping pollutants and causing unhealthy air in cities.
They form over cold ground at night or in winter, or near coasts where cold seawater cools the air above it.
The cooler, denser air is trapped beneath warmer, less dense air, preventing mixing with the stratosphere.
Salt Lake City experiences winter inversions, where the valley is covered in fog-like clouds while the mountains are clear.

A temperature inversion trapping pollutants over a city.

Altitude and Temperature

Air temperature falls at higher altitudes because air is less dense, so its molecules collide less often and produce less heat.
Latitude is not the only factor in climate — altitude matters too.
Mount Kilimanjaro sits only about 3° south of the equator, yet its 6-kilometer peak is capped with snow year-round.
A single mountain can have very different climates at its base and at its summit.

Air temperature vs. height

Mountains and Precipitation

Mountains can cast a rain shadow: as prevailing winds push warm, moist air up the windward side, the air cools and drops its moisture as precipitation.
By the time the air crosses the peak, it has lost most of its moisture.
On the leeward (far) side, the now-dry air sinks and warms, so very little precipitation falls there.
Rain shadows are a geographic factor, alongside latitude and ocean currents, that shape a region's climate.

The rain shadow effect

Climate Definition

Climate is the 30-year average of weather conditions in an area.
Climate is determined by atmospheric and oceanic circulation, along with geographical factors.
The transfer of energy from the equator to the poles, combined with other factors, creates areas with common weather patterns.
Understanding climate requires considering both the atmosphere and the ocean as interconnected systems.

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Preguntas de práctica

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1.What is the 30-year average of weather in an area called?
Easy
- AClimate
- BWeather
- CTemperature
- DPrecipitation
2.Which of the following best describes latitude?
Easy
- ADistance north or south of the equator, measured in degrees
- BDistance east or west of the prime meridian, measured in degrees
- CHeight above sea level
- DThe amount of solar energy received at a location
3.Surface currents are created by global wind patterns and the rotation of the Earth.
Easy
True or false?
4.Why do places near the equator receive more solar energy than places near the poles?
Easy
- AThe Sun's rays strike the equator more directly, focusing energy over a smaller area.
- BThe equator is closer to the Sun.
- CThe equator has more hours of daylight each day.
- DThe atmosphere is thinner at the equator.
5.Match each term with its correct description.
Easy
- Climate
- Weather
- Latitude
- 30-year average of weather
- Current atmospheric conditions
- Distance from the equator
6.What is the primary reason that warm air rises and cool air sinks?
Medium
- AWarm air is less dense than cool air.
- BWarm air is denser than cool air.
- CWarm air contains more water vapor.
- DCool air has more pressure.
7.The Gulf Stream is a cold ocean current that flows from the poles toward the equator.
Easy
True or false?
8.Which of the following best explains why London has a milder winter than Quebec, despite being at a similar latitude?
Medium
- ALondon is warmed by the Gulf Stream.
- BLondon is closer to the equator.
- CQuebec is at a higher altitude.
- DLondon receives more direct sunlight.

Más preguntas

9.Which of the following are factors that influence the formation of surface currents? (Select all that apply)
Medium
- AGlobal wind patterns
- BEarth's rotation
- CTides
- DDifferences in water density due to temperature and salinity
10.Arrange the following steps in the formation of a rain shadow in the correct order.
Medium
- Air rises up the mountain range and cools.
- Precipitation falls on the windward side.
- Air sinks on the leeward side, becoming dry.
- Warm, moist air approaches the mountain.
11.Why are temperature inversions stable?
Medium
- ACold dense air is trapped beneath warmer, less dense air.
- BWarm air rises easily through cold air.
- CThe air is mixed by strong winds.
- DThe ground is warmer than the air above.
12.Which of the following best describes the role of the global conveyor belt in climate?
Medium
- AIt transfers heat from the equator to the poles through ocean currents.
- BIt causes winds to blow from west to east.
- CIt creates temperature inversions near coasts.
- DIt reflects sunlight back into space.
13.Match each pressure belt with its typical precipitation pattern.
Medium
- Equatorial low (ITCZ)
- Subtropical high
- Polar high
- Abundant precipitation in all seasons
- Dry in all seasons
- Sparse precipitation in all seasons
14.Global winds are unpredictable and change direction frequently.
Medium
True or false?
15.Which of the following are effects of the Gulf Stream? (Select all that apply)
Medium
- AIt raises air temperatures over land in Europe.
- BIt brings heavy rainfall to London.
- CIt causes Quebec to have a milder winter.
- DIt transports more than 100 times the world's energy demand.
16.Which statement correctly describes the relationship between latitude and temperature?
Medium
- AAs latitude increases, temperature generally decreases.
- BAs latitude increases, temperature generally increases.
- CLatitude has no effect on temperature.
- DTemperature is highest at the poles.
17.Arrange the steps of the global conveyor belt in order.
Medium
- Water sinks at high latitudes.
- Warm water moves from equator toward poles.
- Water freezes, becoming salty and dense.
- Deep water slowly returns to the equator.
18.Temperature inversions can trap pollutants and produce unhealthy air conditions in cities.
Medium
True or false?
19.Which of the following best explains why Salt Lake City experiences temperature inversions in winter?
Hard
- ACold ground cools the air above it, making it denser than the air above.
- BWarm air rises from the valley, trapping cold air aloft.
- CThe city is located near the ocean.
- DThe mountains block all wind, preventing mixing.
20.Which of the following are examples of regional climate patterns mentioned in the source? (Select all that apply)
Medium
- ALake-effect snow
- BWintertime temperature inversions
- CMonsoon rains
- DRain shadows
21.Why does the air cool as it rises up a mountain?
Medium
- AThe air expands and its molecules have fewer collisions.
- BThe air is closer to the sun.
- CThe air loses water vapor.
- DThe air is pushed by winds.
22.Surface currents are affected by weather and change during large storms.
Medium
True or false?
23.Which of the following best explains why the poles are colder than the equator?
Hard
- AThe Sun's rays strike the poles at a low angle, spreading energy over a larger area.
- BThe poles are farther from the Sun.
- CThe poles have more clouds.
- DThe poles have longer nights.
24.Which of the following conditions can cause a temperature inversion? (Select all that apply)
Hard
- ACold ground cooling the air above it at night
- BCold seawater cooling the air above it near the coast
- CWarm air rising from the surface
- DA river valley running north to south
25.Arrange the steps of the formation of a temperature inversion over land at night.
Hard
- The ground cools the air directly above it.
- The cooled air becomes denser than the air above.
- Warm air sits over the cold air.
- The ground loses heat rapidly at night.
26.Match each factor with its effect on temperature.
Easy
- Latitude
- Altitude
- Ocean currents
- Higher latitude leads to lower temperature
- Higher altitude leads to lower temperature
- Warm currents raise coastal temperatures
27.The Gulf Stream is about 160 kilometers wide and about a kilometer deep.
Easy
True or false?
28.Which of the following best describes why the peak of Mount Kilimanjaro, near the equator, is covered with snow?
Medium
- AIt is at a high latitude
- BIt is at a high altitude
- CIt is near the ocean
- DIt is in the rain shadow of a mountain range
29.Which of the following best explains why the leeward side of a mountain range has very little precipitation?
Medium
- AThe air is warm and dry as it sinks on the leeward side
- BThe air rises and cools, causing condensation
- CThe wind blows from the leeward side
- DThe leeward side is closer to the equator
30.The Gulf Stream transfers more than 100 times the world's energy demand. If the world's energy demand is approximately 20 terawatts (TW), what is the minimum energy transfer of the Gulf Stream in terawatts?
Medium
- A200 TW
- B2,000 TW
- C20,000 TW
- D200,000 TW
31.A city at 45°N receives an average January temperature of -5°C. Another city at the same latitude but influenced by a warm ocean current receives an average January temperature of 3°C. What is the most likely explanation for this temperature difference?
Medium
- AThe city with the warmer temperature is at a higher altitude.
- BThe city with the warmer temperature is influenced by a warm ocean current.
- CThe city with the warmer temperature is closer to the equator.
- DThe city with the warmer temperature receives more direct sunlight.
32.Complete the sentence with the correct terms.
Easy
The overall movement of air forms a series of ____ cells. When averaged out, you get three main air cells in the northern hemisphere and three in the southern hemisphere.
33.Complete the sentence about the global conveyor belt.
Medium
In the global conveyor belt, water freezes at the poles, becomes ____ and dense, then sinks and slowly makes its way back to the equator.
34.What is the name for the phenomenon in which air temperature in the troposphere increases with altitude, so warm air sits over cold air?
Easy
35.Latitude is measured in degrees from 0° to what maximum value?
Easy
36.Complete the sentence about air temperature and altitude.
Medium
Air temperature ____ at higher altitudes because air is less dense and molecules have fewer collisions.
37.The Gulf Stream is about how many kilometers wide?
Medium
38.Complete the sentence about the atmosphere and hydrosphere.
Medium
The atmosphere and hydrosphere make a system that together moves incoming heat from the sun from the ____ out across the planet.
39.What is the name for the large-scale ocean circulation pattern that moves water from the equator to the poles and back?
Medium
40.The Gulf Stream raises air temperatures over land by how many degrees Celsius?
Medium
41.Complete the sentence about the troposphere.
Medium
At the top of the troposphere is a thin layer in which the temperature does not change with height, trapping cooler, denser air beneath warmer, less dense air of the ____.
42.Describe how the unequal heating of Earth's surface leads to atmospheric circulation.
Medium
43.Explain why the peak of Mount Kilimanjaro, near the equator, is covered with snow.
Hard
44.Describe how the unequal heating of Earth's surface drives both atmospheric and oceanic circulation.
Hard
45.Latitude is measured in degrees from 0° to what maximum value?
Easy
- A108 °
- B81 °
- C90 °
- D99 °
46.The Gulf Stream is about how many kilometers wide?
Medium
- A144 km
- B160 km
- C176 km
- D192 km
47.The Gulf Stream raises air temperatures over land by how many degrees Celsius?
Medium
- A3 °C
- B5 °C
- C4 °C
- D2 °C
48.The map shows two U.S. cities at similar latitudes: Los Angeles and Oklahoma City. Compared to Oklahoma City, is Los Angeles expected to have cooler or warmer summers?
Medium
- ACooler summers
- BWarmer summers
49.This difference is due mainly to a difference in the two cities'...
Medium
- ALatitude
- BDistance from the ocean
50.Bare rock and soil warm up more than nearby ice and snow, because ice and snow reflect much of the Sun's energy while darker rock and soil absorb it. Explain how this unequal heating between exposed land and ice can contribute to a warmer local climate over time.
Medium

Apuntes de repaso

## Climate and Global Circulation - **Unequal heating** by the Sun and Earth's rotation drive atmospheric and ocean circulation, redistributing heat from the tropics to the poles. - **Three circulation cells per hemisphere:** Hadley, Ferrel, and Polar cells. ### Hadley Cell - **Location:** 0°–30° latitude. - **Process:** Warm, moist air rises at the equator (low pressure), moves poleward aloft, cools, and descends at ~30° (high pressure). Surface air flows back toward the equator, deflected west by Coriolis → **trade winds** (easterlies). - Shifts north/south with the thermal equator. ### Polar Cell - **Location:** 60°–90° latitude. - **Process:** Air rises at ~60° (low pressure), moves poleward aloft, cools, and descends at the poles (high pressure). Surface air flows toward 60°, deflected west → **polar easterlies**. - Creates cold, dry conditions; record low −89.2°C in Antarctica. ### Ferrel Cell - **Location:** 30°–60° latitude. - **Process:** Surface air flows poleward from the horse latitudes (30°), deflected east → **prevailing westerlies**. Air rises at ~60° and returns aloft toward 30°. ### Key Concepts - **Coriolis effect:** Deflects moving air to the right in the Northern Hemisphere, left in the Southern. - **Horse latitudes:** High-pressure zones at ~30° with light winds and little rain. - **Jet streams:** Fast, narrow air currents at the boundary between cells (e.g., polar jet stream). - **Thermal equator:** Zone of maximum heating; shifts seasonally. - **Rossby waves:** Large-scale waves in the atmosphere that influence jet stream paths. ### Summary Table | Cell | Latitude | Surface Winds | Pressure | |---------|----------|---------------------|----------| | Hadley | 0°–30° | Trade winds (E) | Low at 0°, high at 30° | | Ferrel | 30°–60° | Westerlies (W) | High at 30°, low at 60° | | Polar | 60°–90° | Polar easterlies (E)| Low at 60°, high at 90° | *Note: Winds named from where they come (e.g., trade winds blow from east to west).*

Hadley cell: A large-scale atmospheric circulation cell that extends from the equator to about 30° latitude, driven by rising warm air at the equator and descending cool air at the subtropics.
Ferrel cell: A mid-latitude atmospheric circulation cell between about 30° and 60° latitude, characterized by surface westerlies and rising air at the polar front.
Polar cell: A high-latitude atmospheric circulation cell from about 60° to 90° latitude, with rising air at 60° and descending cold air at the poles, producing polar easterlies.
Coriolis effect: The deflection of moving air (or water) due to Earth's rotation; to the right in the Northern Hemisphere, to the left in the Southern Hemisphere.
Trade winds: Steady easterly winds that blow from the subtropical high-pressure belts toward the equator, part of the Hadley cell.
Polar easterlies: Cold, dry winds that blow from the polar high-pressure areas toward lower latitudes, deflected west by the Coriolis effect.
Prevailing westerlies: Winds that blow from the west in the mid-latitudes (30°–60°), part of the Ferrel cell.
Horse latitudes: Subtropical high-pressure belts at about 30°–35° latitude, characterized by light winds and little precipitation.
Jet stream: A narrow, fast-moving air current in the upper troposphere, often found at the boundary between circulation cells (e.g., polar jet stream).
Thermal equator: The zone of maximum solar heating on Earth, which shifts seasonally north and south of the geographic equator.
Rossby waves: Large-scale, meandering waves in the atmosphere that influence the path of jet streams and weather systems.

Tarjetas

What drives atmospheric circulation?

Unequal heating of Earth's surface by the Sun and the rotation of Earth drive atmospheric circulation.

What are the three major atmospheric circulation cells in each hemisphere?

The Hadley cell, Ferrel cell, and polar cell.

Where is the Hadley cell located?

The Hadley cell is located near the equator, extending from about 0° to 30° latitude in each hemisphere.

Describe the movement of air in the Hadley cell.

Warm, moist air rises at the equator, moves poleward in the upper troposphere, cools and descends at about 30° latitude, then flows back toward the equator along the surface.

What causes the trade winds?

The trade winds are the surface winds in the Hadley cell that blow from the east toward the equator due to the Coriolis effect.

What are the horse latitudes?

The horse latitudes are high-pressure zones at about 30° to 35° latitude where winds diverge, typically with light winds and little precipitation.

Describe the polar cell.

At about 60° latitude, air rises, moves poleward in the upper atmosphere, cools and descends at the poles, then flows back toward 60° latitude along the surface.

What are polar easterlies?

Polar easterlies are surface winds in the polar cell that blow from the east (from the poles toward 60° latitude) due to the Coriolis effect.

What is the Coriolis effect?

The Coriolis effect is the deflection of moving air (or water) due to Earth's rotation, causing winds to curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

How does the Coriolis effect influence global wind patterns?

It causes surface winds in the Hadley cell to blow from the east (trade winds), in the Ferrel cell from the west (westerlies), and in the polar cell from the east (polar easterlies).

What is the role of atmospheric circulation in redistributing heat?

Atmospheric circulation moves thermal energy from the equator toward the poles, balancing Earth's temperature distribution.

What is the thermal equator?

The thermal equator is the zone of greatest heating on Earth, which shifts north and south with the seasons.

How does the Hadley cell shift seasonally?

The Hadley cell shifts northward in June/July and southward in December/January, following the Sun's heating.

What are Rossby waves?

Rossby waves are large-scale waves in the atmosphere that influence the path of the polar jet stream.

What is the polar jet stream?

The polar jet stream is a fast-moving air current in the upper atmosphere, located between the Ferrel and polar cells, that influences weather patterns.

How does ocean circulation relate to atmospheric circulation?

Ocean circulation works together with atmospheric circulation to redistribute thermal energy around Earth.

What causes the rising of air at the equator?

Intense solar heating at the equator warms the air, causing it to expand, decrease in density, and rise.

Why does descending air create high pressure?

Descending air becomes denser and compresses, increasing surface pressure, which typically leads to clear skies and dry conditions.

What is a heat engine in the context of atmospheric circulation?

Earth's atmosphere acts as a heat engine driven by solar energy, with the Sun as the heat source and space as the heat sink, producing motion that redistributes heat.

How do tectonic uplift and plate tectonics affect atmospheric circulation over long timescales?

Tectonic uplift can alter jet streams, and plate tectonics can shift ocean currents, potentially changing major circulation patterns over hundreds of millions of years.

What is the approximate power of the Hadley cell as a heat engine?

The Hadley system is estimated to have a power of about 200 terawatts.

Why can't long-range weather predictions be made beyond ten days?

Small-scale weather systems are chaotic, and due to chaos theory (butterfly effect), predictions become unreliable beyond about ten days.

What is the lowest temperature recorded on Earth, and where was it measured?

−89.2 °C at Vostok Station in Antarctica, measured in 1983.

How does the polar cell contribute to cold surface temperatures in Antarctica?

The polar cell, combined with terrain and katabatic winds, creates very cold conditions at the surface.

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