Detailed Explanation:

Answer: Option 1 — Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

The troposphere is indeed thicker at the equator (approximately 16-18 km) compared to the poles (approximately 8-10 km) due to differential heating and thermal expansion. The intense solar radiation at the equator generates strong convectional currents that transport heat vertically to great heights, causing the air to expand and thereby increasing the thickness of the troposphere. Statement-II provides a direct causal explanation for the phenomenon described in Statement-I.

✅ Statement-I – Correct: The troposphere's thickness at the equator (16-18 km) is significantly greater than at the poles (8-10 km) due to greater heating and air expansion.
✅ Statement-II – Correct: Strong convectional currents at the equator, driven by intense solar heating, transport heat vertically to great heights, directly causing the increased tropospheric thickness.

📝 Short Notes: Troposphere and Atmospheric Structure

• Troposphere Characteristics: The lowest layer of the atmosphere where all weather phenomena occur, containing approximately 75% of the atmosphere's mass and almost all water vapor.
• Thickness Variation: Troposphere thickness varies from 8-10 km at the poles to 16-18 km at the equator, averaging about 13 km globally.
• Equatorial Heating: The equator receives more direct and intense solar radiation throughout the year, causing maximum surface heating and air temperature.
• Convectional Currents: Hot air at the equator rises rapidly due to lower density, creating strong vertical currents that transport heat to higher altitudes (part of the Hadley Cell circulation).
• Thermal Expansion: Warmer air occupies greater volume, causing the atmospheric column to expand vertically at the equator, increasing tropospheric height.
• Temperature Lapse Rate: Temperature decreases with altitude in the troposphere at an average rate of 6.5°C per kilometer until reaching the tropopause.
• Tropopause Variation: The tropopause (boundary between troposphere and stratosphere) is higher and colder at the equator (-80°C) than at the poles (-45°C).