Why is the Saturated Adiabatic Lapse Rate lower than the Dry Adiabatic Lapse Rate?

The Saturated Adiabatic Lapse Rate (SALR) is indeed lower than the Dry Adiabatic Lapse Rate (DALR) primarily because the air is warming by condensation. When air rises and cools to its dew point, it becomes saturated, and condensation of water vapor into liquid water releases latent heat. This release of heat offsets some of the cooling that would typically occur due to the rising air parcel expanding in the lower pressure environment.

In contrast, the Dry Adiabatic Lapse Rate applies to unsaturated air. As dry air rises, it cools at a constant rate of approximately 9.8 degrees Celsius per kilometer. Once the air becomes saturated, the process of condensation occurs, which means that less heat is lost than would occur in dry air, resulting in a slower rate of temperature decline. Therefore, the presence of latent heat release during condensation is what leads to the lower lapse rate when compared to the DALR.

This difference in rates highlights the role of moisture in atmospheric processes and the impact of latent heat on temperature changes and stability in the atmosphere.