The dry adiabatic rate (DAR) is 5.5 degrees F per 1000 feet. The saturated adiabatic rate (SAR) is 3.3 degrees F per 1000 feet. Why is SAR lower than DAR?

To understand why the saturated adiabatic rate (SAR) is lower than the dry adiabatic rate (DAR), let's first establish what these rates represent. Both the DAR and SAR are measures of how temperature changes with altitude in a rising or descending parcel of air.

1. Dry Adiabatic Rate (DAR):
- The DAR assumes that no condensation or evaporation of water occurs within the parcel of air.
- It is also known as the lapse rate, representing the rate at which the air temperature decreases with increasing altitude.
- The DAR is approximately 5.5 degrees Fahrenheit per 1000 feet (or 10 degrees Celsius per 1000 meters).

2. Saturated Adiabatic Rate (SAR):
- The SAR takes into account the condensation or evaporation of water vapor within the parcel of air.
- As the air rises and encounters a lower pressure at higher altitudes, it expands and cools down.
- When the temperature decreases, the relative humidity increases, leading to the saturation of the air parcel.
- Saturation occurs when the air reaches its dew point temperature, and the water vapor within the air condenses into visible water droplets forming clouds.
- Once the air becomes saturated, latent heat is released due to condensation, which slows down the cooling process.
- The SAR is lower than the DAR because the release of latent heat counteracts some of the cooling effect of rising air.

In summary, the SAR is lower than the DAR because as the air rises and becomes saturated, the release of latent heat from condensation offsets some of the cooling process. This release of latent heat slows down the cooling rate compared to the DAR, resulting in a lower temperature decrease with increasing altitude.