Which factor primarily influences the decrease of density in a column of air as altitude increases?

• A. Temperature
• B. Humidity
• C. Pressure
• D. Wind speed

Answer: (C)

The primary factor influencing the decrease of density in a column of air as altitude increases is pressure. As altitude increases, the atmospheric pressure decreases due to the weight of the air above pressing down. This reduction in pressure leads to a decrease in air density because the number of air molecules in a given volume becomes less.

At higher altitudes, while temperature and humidity can also play roles, they do not have as direct an effect on density under typical conditions. Temperature can impact density; warmer air is less dense than cooler air. However, the fundamental concept that density decreases with altitude is governed primarily by the decrease in atmospheric pressure. Wind speed affects how air moves but does not directly influence the overall density of the air column at varying altitudes.