Question

The world's major subsidence zones occur at the latitudes a. \(0^{\circ}\) and \(45^{\circ}-55^{\circ}\) b. \(30^{\circ}\) and the poles. c. \(0^{\circ}\) and the poles. d. \(20^{\circ}-30^{\circ}\) and \(45^{\circ}-55^{\circ}\) e. \(0^{\circ}\) and \(20^{\circ}-30^{\circ}\)

Short answer

The correct answer is option b. \(30^{\circ}\) and the poles.

Step-by-step solution

Identify the latitude degrees associated with the major atmospheric cells.

The major atmospheric cells on Earth are: Hadley cells (from 0° to 30°), Ferrel cells (from 30° to 60°), and Polar cells (from 60° to 90°). Subsidence zones would be most likely found where air descends, which happens at the edges of these cells.

Connect these latitude degrees to the given options.

Connect the areas of descending air to the given options. At the equator lies the start of the Hadley cell (0°), it ends at around 30°, which marks a point of air subsidence, followed by another zone of subsidence around the edge between the Ferrel and Polar cell, close to the poles (around 60° to 90°).

Choose the appropriate answer

The correct answer corresponds to the major subsidence zones on Earth, which occur at around 30° (end of Hadley cell) and at the poles (end of Ferrel cell, start of Polar cell).

Key concepts

Atmospheric Cells

Atmospheric cells are large-scale circulatory patterns in the Earth's atmosphere. They play a crucial role in distributing heat and energy around the planet. There are three main types of atmospheric cells: Hadley, Ferrel, and Polar cells. Each cell operates between specific latitudinal ranges and affects climate and weather patterns in its region. The pattern of these cells creates areas of rising and descending air.

• Rising Air: Warm air that rises usually leads to areas of low pressure and cloud formation.
• Descending Air: Cold air that descends tends to create high-pressure zones, often resulting in drier conditions.

Understanding these dynamics is essential for comprehending why certain regions of the Earth are wet or dry, like the rainforests and deserts.

Hadley Cell

The Hadley cell is the first type of atmospheric circulation cell. It spans from the equator to about the 30° latitude in both hemispheres. It is crucial in creating major subsidence zones. Warm air rises at the equator, where solar heating is intense, causing low-pressure zones and heavy rainfall. This air travels poleward in the upper atmosphere.
Eventually, the air cools and descends at approximately 30° latitude, creating high-pressure zones. This subsidence of air leads to arid climates, explaining why many of the world's deserts are found around this latitude.

• Key Feature: Movement from equator to 30° latitude.
• Effects: Creates deserts and subtropical high-pressure zones.

The pattern of rising and descending air within the Hadley cell is critical for shaping global climate.

Ferrel Cell

The Ferrel cell operates between the Hadley and Polar cells, approximately between 30° and 60° latitude. It acts as a transport zone for air masses due to indirect energy transfer. In the Ferrel cell, surface air converges at around 60° latitude, causing it to rise. This rising air creates low-pressure zones and precipitation in areas like the temperate zones.
At around 30° latitude, the air descends, converging with the downward movement of the Hadley cell and contributing to its high-pressure zones. These transitions impact weather patterns significantly by fostering rainy regions at higher latitudes.

• Key Feature: Situated between 30° and 60° latitude.
• Effects: Creates temperate climates and transfers warm and cold air masses.

This complexity makes the Ferrel cell less predictable than the Hadley or Polar cells.

Polar Cell

The Polar cell forms the final part of the atmospheric circulation system, occurring between 60° and 90° latitude near the poles. It originates from the cooling and subsidence of air at the poles, which creates areas of high pressure. This process drives cold air toward lower latitudes, where it converges with the Ferrel cell air.
The rising air creates low-pressure zones around the 60° latitude, contributing to expansive cloud cover and precipitation in these regions.

• Key Feature: Exists from 60° to 90° latitude, near the poles.
• Effects: Contributes to colder climates and polar vortex stability.

The dynamics within the Polar cell help in maintaining the Earth's heat balance by directing cold air toward mid-latitudes.