The correct option is 2 and 3 only.
Explanation
The atmosphere consists of concentric layers of air with varying density and temperature. The Tropopause is the transitional boundary separating the lowest layer, the Troposphere, from the overlying Stratosphere. It marks the point where the atmospheric temperature stops decreasing with altitude and remains constant or begins to increase.
Statement-wise Analysis:
- Statement 1 is Incorrect. The Tropopause is the zone separating the Troposphere from the Stratosphere. The boundary separating the Stratosphere from the Mesosphere is called the Stratopause.
- Statement 2 is Correct. The height of the troposphere is approximately 18 km at the equator and 8 km at the poles. Since temperature decreases with altitude in the troposphere (Normal Lapse Rate), the air at the top of the troposphere over the equator travels a greater vertical distance, cooling significantly more than the air over the poles. Consequently, the temperature at the tropopause is roughly minus 80°C over the equator and about minus 45°C over the poles.
- Statement 3 is Correct. The height of the tropopause is determined by convection currents and the heat of the surface. During summer, intense heating causes air to expand and convection currents to rise higher, pushing the tropopause upward. In winter, the air contracts, and the tropopause lowers. Thus, the height varies seasonally.
Key Takeaway:
The Tropopause is significantly colder and higher over the equator compared to the poles because strong convection currents at the equator push the air to greater altitudes, allowing for prolonged cooling.