What is density altitude?

Density altitude is the height at which a particular air density occurs in the standard atmosphere. This concept is crucial for pilots and meteorologists, as it helps them understand how performance can be affected by variations in air density due to temperature, pressure, and humidity.

When aircraft operate in lower air density conditions (which can be caused by high temperatures, high altitudes, and humidity), they experience reduced performance, including less lift from the wings and decreased engine efficiency. Density altitude provides a standardized way to assess these challenges by expressing the air density in terms of altitude in the standard atmosphere.

In contrast, the other options do not accurately define density altitude. The concept involves more than just humidity (that would imply adjustments based on moisture content) or just local temperature or atmospheric pressure. Instead, density altitude is a comprehensive measure that reflects the combined effect of pressure and temperature on air density, thereby providing a clear and useful metric for aviation operations.