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 the temperature gradient or temperature changes with altitude. (b) The atmosphere is divided into five major regions: 1. Troposphere: from Earth's surface up to approximately 8-14.5 km altitude. 2. Stratosphere: from around 8-14.5 km to approximately 50 km altitude. 3. Mesosphere: from about 50 km to roughly 85 km altitude. 4. Thermosphere: from around 85 km to approximately 600 km altitude. 5. Exosphere: from around 600 km to about 10,000 km altitude.

Step-by-step solution

(a) Primary basis for division of the atmosphere

The primary basis for the division of the atmosphere into different regions is the temperature gradient or temperature changes with altitude. Different layers of the atmosphere exhibit different temperature characteristics, which is the main reason for their categorization.

(b) Regions of the atmosphere and their altitude intervals

The atmosphere is divided into five major regions, based on temperature characteristics and altitude: 1. Troposphere: The troposphere is the lowest layer of the atmosphere, extending from the Earth's surface up to an altitude of approximately 8-14.5 km, depending on the location (higher at the equator and lower at the poles). The temperature in this region decreases with increasing altitude. 2. Stratosphere: The stratosphere lies above the troposphere, with its lower boundary starting at around 8-14.5 km, and extending to approximately 50 km. The temperature in this region increases with altitude due to the presence of the ozone layer, which absorbs ultraviolet radiation from the Sun. 3. Mesosphere: The mesosphere is located above the stratosphere, with its base at about 50 km and extending up to roughly 85 km. The temperature in this region decreases with altitude, with the top of the mesosphere being the coldest part of the atmosphere. 4. Thermosphere: The thermosphere starts at around 85 km and extends up to approximately 600 km. This layer experiences a significant increase in temperature with altitude due to the absorption of highly energetic solar radiation by its sparse gas molecules. 5. Exosphere: The exosphere is the outermost region of the atmosphere, starting at around 600 km and extending up to about 10,000 km. This is the transition region between Earth's atmosphere and outer space. The temperature in this region is highly variable, depending primarily on solar activity. Note that the boundaries between these regions are not sharp, and there are transition zones called "pauses" between these layers.

Key concepts

Troposphere

The troposphere is the lowest atmospheric layer where we live and breathe. This region extends from the Earth's surface up to heights of about 8 to 14.5 kilometers, depending mostly on the geographical location. For instance, it's thicker at the equator and thinner at the poles.
In the troposphere, the temperature drops as you go higher. This gradient occurs because the sun heats the Earth's surface, which then warms the air above it. Most of our weather, including clouds, rain, and wind, happens in this layer, thanks to the moisture and temperature variations. 🌧️

• Lowest atmospheric layer
• Altitude: 8-14.5 km
• Decreasing temperature with altitude
• Site of weather phenomena

Stratosphere

Above the troposphere lies the stratosphere, extending from about 8 to 14.5 kilometers up to 50 kilometers. In this layer, the temperature pattern is different from the troposphere's. Here, the temperature actually rises with altitude. 🌡️ This warming is due to the presence of the ozone layer, which absorbs and scatters the sun's ultraviolet (UV) radiation. This makes the stratosphere home to the critical ozone layer, shielding the Earth from harmful solar rays. Jet aircraft often travel in this region because it is very stable and free from weather disturbances.

• Second atmospheric layer
• Altitude: 8-14.5 km to 50 km
• Increasing temperature due to the ozone layer
• Often used by jet aircraft

Mesosphere

The mesosphere stretches from 50 kilometers up to about 85 kilometers above Earth. In this layer, temperatures decrease as altitude increases, making it the coldest region of the atmosphere. ❄️
Despite being less understood, it is important for burning meteoroids. Shooting stars, or meteorites, famously burn up in this layer due to atmospheric friction. Scientists often study this layer using sounding rockets to learn more about its properties.

• Third atmospheric layer
• Altitude: 50 km to 85 km
• Decreasing temperature
• Site of meteorite disintegration

Thermosphere

The thermosphere extends from approximately 85 kilometers to around 600 kilometers above the Earth. Here, temperatures drastically increase with altitude because the few air molecules present absorb intense solar radiation. ☀️
This layer is well known for its role in aurora phenomena like the Northern and Southern Lights, where charged particles from the sun interact with Earth's magnetic field. The International Space Station orbits within this layer, but despite high temperatures, it would feel very cold due to the sparse atmosphere.

• Fourth atmospheric layer
• Altitude: 85 km to 600 km
• Increasing temperature due to solar energy absorption
• Aurora occurrences and space station orbits here

Exosphere

Beyond the thermosphere, the exosphere ranges from about 600 kilometers to as far as 10,000 kilometers, eventually blending into outer space. This layer acts as the outer edge of Earth's atmosphere, transitioning into the vacuum of space. Here, air molecules are extremely sparse, and temperatures can vary wildly depending on solar activity. Unlike other layers, the exosphere is more spaced out and less dense, making it a key region for satellites orbiting Earth.
The exosphere is an intriguing frontier between our planet and cosmic emptiness, reminding us of the vastness of outer space.

• Outermost atmospheric layer
• Altitude: 600 km to 10,000 km
• Variable temperatures
• Sparse contains satellites