As altitude increases, which statement about air properties is true?

As altitude increases, which statement about air properties is true?

• A. Both temperature and density decrease
• B. Temperature decreases while density increases
• C. Both temperature and density increase
• D. Temperature increases while density decreases

Answer: (A)

As altitude increases, air becomes thinner and cooler in the lower atmosphere. Pressure drops with height, so the air expands and density decreases. In the troposphere, the temperature also falls with height due to the lapse rate, so the air gets cooler as you climb. Since both density and temperature decrease in this part of the atmosphere, the statement that both temperature and density decrease is the best choice for typical drone operating conditions. Behind this the nuance is that in higher layers like the stratosphere, temperature can rise with altitude while density still falls; but for common flight envelopes, both properties trend downward with height.

As altitude increases, air becomes thinner and cooler in the lower atmosphere. Pressure drops with height, so the air expands and density decreases. In the troposphere, the temperature also falls with height due to the lapse rate, so the air gets cooler as you climb. Since both density and temperature decrease in this part of the atmosphere, the statement that both temperature and density decrease is the best choice for typical drone operating conditions. Behind this the nuance is that in higher layers like the stratosphere, temperature can rise with altitude while density still falls; but for common flight envelopes, both properties trend downward with height.