What is the term for the lapse rate that is not constant?

The moist adiabatic lapse rate refers to the rate at which a parcel of air cools as it rises when it contains water vapor. Unlike the dry adiabatic lapse rate, which is a constant rate of cooling (approximately 9.8°C per kilometer), the moist adiabatic lapse rate can vary based on the moisture content of the air. As the air parcel rises and expands, it cools, but when it is saturated with water vapor, the cooling rate is less due to the release of latent heat during condensation. This means that the lapse rate in moist air is not a fixed value and can change depending on factors like temperature and humidity levels. This concept is crucial in meteorology as it helps in understanding the behavior of clouds and precipitation.

The other options describe specific, consistent rate conditions or phenomena. For example, the dry adiabatic lapse rate applies when air is dry and rising without condensation taking place, while the environmental lapse rate describes the actual rate of temperature decrease with altitude in the atmosphere at a given time and location, which can also vary but does not apply specifically to moist conditions. The standard lapse rate is a theoretical average value used for simplified calculations that does not reflect variability in moisture conditions.