The correct option is Temperature decreases with altitude..
Explanation
The Earth's atmosphere is divided into distinct layers based on the vertical temperature gradient. The Mesosphere is the third layer, situated above the Stratosphere and below the Thermosphere, extending approximately from 50 km to 80 km above sea level.
- Temperature Trend: In the Mesosphere, the temperature decreases with an increase in altitude.
- Scientific Basis: Unlike the Stratosphere, the Mesosphere contains negligible amounts of ozone and water vapor to absorb solar radiation. Additionally, radiative cooling by carbon dioxide becomes effective in this layer. As a result, the heat source diminishes with height, leading to a drop in temperature.
- Mesopause: The upper boundary of the Mesosphere, known as the Mesopause, represents the coldest point in the Earth's atmosphere, where temperatures can drop to approximately -100°C.
Comparison with Adjacent Layers:
- Stratosphere (Below): Temperature increases with altitude due to the absorption of UV radiation by the ozone layer.
- Thermosphere (Above): Temperature increases drastically with altitude due to the absorption of high-energy solar radiation (X-rays and UV) by atomic oxygen and nitrogen.
Key Takeaway: The Mesosphere is characterized by a negative thermal gradient, meaning temperature falls as altitude rises, distinguishing it from the layers immediately above and below it.