What does ISA temperature deviation measure?

ISA temperature deviation specifically measures the difference between the actual temperature at a given altitude and the International Standard Atmosphere (ISA) temperature at that same altitude. The ISA serves as a reference model for the standard atmosphere's temperature profile with altitude, which is crucial for various aviation and meteorological applications. Understanding this deviation is important for tasks such as performance calculations for aircraft, where variations from the ISA can impact lift, engine performance, and overall flight dynamics.

Other options address different concepts that do not align with this specific measurement. For example, measuring the difference between sea level and altitude temperature does not focus on a specific altitude's comparison with the ISA, which is what this deviation entails. Similarly, differences in daily temperatures or average temperatures at various altitudes do not pertain directly to ISA temperature deviation.