Correct Option
The correct option is Normal Lapse Rate.
Explanation
The atmosphere is primarily heated from below by terrestrial radiation emitted by the Earth's surface. Consequently, in the troposphere, temperature typically decreases as altitude increases. This vertical temperature gradient is a fundamental characteristic of the lower atmosphere.
Option Analysis
- Temperature Inversion Temperature Inversion: Incorrect. This phenomenon occurs when the normal temperature gradient is reversed, meaning temperature increases with altitude rather than decreasing.
- Normal Lapse Rate Normal Lapse Rate: Correct. This is the average rate at which temperature decreases with increasing height in the troposphere. The standard value is approximately 6.5°C per 1,000 meters (or roughly 1°C for every 165 meters).
- Advection Advection: Incorrect. Advection refers to the transfer of heat through the horizontal movement of air (e.g., wind transporting warm or cold air masses), not the vertical temperature profile.
- Thermal Anomaly Thermal Anomaly: Incorrect. A thermal anomaly represents the deviation of a specific location's temperature from the mean temperature of its latitude; it does not describe the vertical change in temperature.
Key Takeaway
Normal Lapse Rate is the standard vertical decrease in temperature in the troposphere, averaging 6.5°C per km, caused by the distance from the Earth's surface (the primary heat source).