Question

(a) What is the primary basis for the division of the atmosphere into different regions? (b) Name the regions of the atmosphere, indicating the altitude interval for each one.

Short answer

(a) The primary basis for the division of the atmosphere into different regions is temperature variation, caused by absorption of solar radiation energy by different gases and altitude. (b) The regions of the atmosphere and their altitude intervals are as follows: 1. Troposphere: \(6-8 \; km\) (poles) and \(16-18 \; km\) (equator) 2. Stratosphere: \(10-18 \; km\) (poles) and \(50 \; km\) (equator) 3. Mesosphere: \(50-85 \; km\) 4. Thermosphere: \(85-600 \; km\) 5. Exosphere: \(600-10,000 \; km\)

Step-by-step solution

(a) Primary Basis for Division of Atmosphere

To understand the primary basis for dividing the atmosphere into different regions, several factors need to be considered, such as temperature, air pressure, and the presence of specific gases. Among these factors, temperature variations play a critical role in determining the layers of the atmosphere. These temperature variations happen due to the absorption of solar radiation energy by different gases and the altitude at which these gases are present in the atmosphere.

(b) Regions of the Atmosphere and Altitude Intervals

The atmosphere is divided into five main regions according to the temperature gradient. Each region has a specific altitude interval: 1. Troposphere: This is the layer where weather occurs and where life on earth generally exists. The altitude intervals for the troposphere vary depending on the location: a. \(6-8 \; km\) (20,000 - 26,000 ft) at the poles b. \(16-18 \; km\) (52,000 - 59,000 ft) at the equator 2. Stratosphere: The second layer of the atmosphere is home to the ozone layer, which protects the earth from harmful solar radiation. The altitude interval for the stratosphere is between: a. \(10-18 \; km\) (33,000 - 59,000 ft) at the poles b. \(50 \; km\) (164,000 ft) at the equator 3. Mesosphere: This layer of the atmosphere is where meteors burn up upon entering the earth's atmosphere. The altitude interval for the mesosphere is approximately: a. \(50-85 \; km\) (164,000 - 279,000 ft) 4. Thermosphere: This layer has a rapid increase in temperature due to solar radiation absorbed by the upper atmosphere. The altitude interval for the thermosphere is approximately: a. \(85-600 \; km\) (279,000 - 1,000,000 ft) 5. Exosphere: The outermost layer of the atmosphere, it eventually merges into space. The altitude interval for the exosphere is approximately: a. \(600-10,000 \; km\) (1,000,000 - 6,000,000 ft)

Key concepts

Temperature Gradient

The atmospheric layers are primarily defined by the temperature gradient. This refers to how temperature changes with altitude. As we move up the atmosphere, the temperature does not rise or fall evenly.
These variations create different temperature profiles that define each atmospheric layer. For instance:

• In the troposphere, temperature decreases with altitude. This is why mountaintops are colder than the valleys below.
• In contrast, the stratosphere, above the troposphere, experiences an increase in temperature with height, due to the ozone layer absorbing solar radiation.
• In the mesosphere, temperatures drop again with higher altitudes.
• The thermosphere sees a rise in temperatures due to the absorption of highly energetic solar radiation.
• Finally, the exosphere has very little matter, so temperature, as traditionally defined, becomes less applicable.

The behavior of temperature in these regions determines the structural division of the atmosphere.

Atmosphere Division

The division of the atmosphere into regions is based largely on the temperature gradient mentioned before. However, other factors, like air composition and pressure changes, also play a role. Let's break down these divisions:

• Troposphere: The lowest layer where we live and weather occurs. Temperature decreases with height.
• Stratosphere: Above the troposphere, housing the ozone layer. Temperature increases with altitude due to ozone absorption of sunlight.
• Mesosphere: Here, temperatures decrease again; it's the middle layer where meteors burn up.
• Thermosphere: High-altitude layer; temperatures increase significantly due to solar energy absorption.
• Exosphere: The outermost layer where atmospheric gases escape into space.

This arrangement allows for the classification of the atmosphere based on continuous changes in environmental conditions such as temperature and pressure.

Altitude Intervals

Each atmospheric layer has specific altitude intervals, which vary slightly depending on geographical location. Understanding these intervals helps in mapping out where phenomena occur:

• Troposphere: Reaches up to about 6-8 km at the poles and 16-18 km at the equator. This is the layer closest to Earth's surface.
• Stratosphere: Extends from about 10-18 km up to about 50 km. It is where jet flights generally travel and where the ozone layer resides.
• Mesosphere: Ranges from around 50 km to 85 km. This is the layer where most meteors start to burn up on entry.
• Thermosphere: Soars from about 85 km to possibly 600 km, heating up due to solar radiation.
• Exosphere: Reaches from around 600 km and fades into space at approximately 10,000 km.

These altitude distinctions are crucial for understanding where each layer's characteristics begin and end, and how they influence our environment.