Understanding Temperature Changes in Earth's Atmosphere

Earth's atmosphere is divided into several layers based on temperature profiles. Two important layers are the troposphere and the stratosphere. Understanding how temperature changes with height in these layers is key to analyzing the given statements.

Temperature Profile in the Troposphere

The troposphere is the lowest layer of the atmosphere, extending from the Earth's surface up to about 7-15 kilometers (depending on latitude and season). Most of the Earth's weather occurs in the troposphere.

• Temperature in the troposphere generally decreases with increasing altitude.
• This decrease is due to the fact that the troposphere is heated from below by the Earth's surface. The surface absorbs solar radiation and re-emits it as heat, warming the air closest to it.
• The rate at which temperature decreases with height is called the lapse rate.
• The average environmental lapse rate in the troposphere is approximately \(6.5^{\circ}\text{C}\) per kilometer, but it can vary significantly depending on local conditions. However, one of the options mentions a specific rate.

Temperature Profile in the Stratosphere

Above the troposphere is the stratosphere, extending up to about 50 kilometers. The boundary between the troposphere and the stratosphere is called the tropopause, where the temperature stops decreasing and starts increasing.

• In the stratosphere, temperature increases with increasing altitude.
• This temperature increase is primarily due to the presence of the ozone layer within the stratosphere.
• Ozone molecules absorb ultraviolet (UV) radiation from the sun. This absorption process converts UV energy into heat, warming the surrounding air.

Analyzing the Statements about Temperature

Let's examine each statement provided:

1. Statement 1: Temperature decreases with height in the stratosphere.

   Based on our understanding, temperature increases with height in the stratosphere due to ozone absorption of UV radiation. Therefore, this statement is incorrect.

2. Statement 2: Temperature is constant at different heights in the stratosphere.

   As explained, temperature increases with height in the stratosphere, it is not constant. Therefore, this statement is incorrect.

3. Statement 3: Temperature increases with height in the troposphere at an average rate of \(6.5^{\circ}\text{C}\) per kilometre.

   Temperature in the troposphere decreases with height, not increases. The average lapse rate is indeed around \(6.5^{\circ}\text{C}\) per kilometre for the rate of decrease, but the statement says it increases. Therefore, this statement is incorrect.

4. Statement 4: Temperature decreases with height in the troposphere at an average rate of \(6.4^{\circ}\text{C}\) per kilometre.

   Temperature in the troposphere does decrease with height. The average environmental lapse rate is commonly stated as approximately \(6.5^{\circ}\text{C}\) per kilometre, but figures around \(6.4^{\circ}\text{C}\) or \(6.49^{\circ}\text{C}\) are also used and considered accurate averages depending on the source and specific conditions being averaged. This statement accurately describes the general trend of temperature decrease with height in the troposphere and provides a reasonable average rate. Therefore, this statement is correct.

Summary of Temperature Profiles

Here is a quick summary of temperature trends in the lower atmosphere layers:

Conclusion on Temperature Statements

Based on the analysis of temperature changes in the troposphere and stratosphere, only the statement describing temperature decreasing with height in the troposphere at an approximate average rate is correct.

Revision Table: Atmospheric Temperature

Additional Information: Atmospheric Layers and Temperature

• The layer above the stratosphere is the mesosphere, where temperature decreases with height.
• Above the mesosphere is the thermosphere, where temperature increases sharply with height.
• The boundaries between these layers are called pauses: tropopause (troposphere/stratosphere), stratopause (stratosphere/mesosphere), and mesopause (mesosphere/thermosphere).
• The temperature profile is one of the key characteristics used to define the different layers of the atmosphere.