Which one of the following statements is correct with reference to normal lapse rate?

The normal lapse rate refers to the standard rate at which air temperature decreases with increasing altitude within the troposphere [2]. Under normal conditions, the atmosphere is primarily heated from the Earth's surface via conduction and radiation; consequently, air temperature is highest at ground level and falls as one moves higher [4]. The average rate of this decrease is approximately 6.5°C per kilometer or 1°C for every 165 meters of ascent [2]. This positive lapse rate is a fundamental characteristic of the troposphere's vertical temperature profile [5]. While conditions like temperature inversion can reverse this trend, causing temperature to increase with height, such instances are considered departures from the 'normal' behavior where the ground remains the warmest point [5].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > 22.2. Lapse Rate > p. 295
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > Altitude > p. 288
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > 22.4. Temperature Inversion > p. 300
4. [4] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > FACTORS INFLUENCTNG TEMPERATURE > p. 134
5. [5] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > INVERSION OF TEMPERATURE > p. 73