Certified Flight Instructor - Flight Instructor Airplane Practice Exam

What is the average lapse rate in the troposphere?

1. 2.0 °C per 1,000 feet

2. 3.0 °C per 1,000 feet

3. 5.4 °C per 1,000 feet

4. 6.5 °C per 1,000 feet

The correct answer is: 2.0 °C per 1,000 feet

The average lapse rate in the troposphere is typically accepted to be around 6.5 °C per 1,000 feet. This value, known as the environmental lapse rate, represents the rate at which air temperature decreases as altitude increases in the lower part of the atmosphere. In this context, understanding the correct lapse rate is crucial for several reasons. First, it helps pilots recognize how temperature changes with altitude can affect aircraft performance, as colder air at higher altitudes can lead to increased density and thus better lift characteristics for a given aircraft. Furthermore, the lapse rate is essential for understanding weather phenomena and forming an accurate picture of atmospheric stability. If, for instance, the actual air temperature is decreasing at a rate significantly different from the average lapse rate, it can indicate the presence of rising air, which is conducive to cloud formation and potential turbulence. Therefore, while other choices suggest lower rates that do not align with the established norm, the correct value indicates a clear understanding of atmospheric processes critical for flight operations and safety.