What happens to the temperature of a rising parcel of air that is not saturated?

When a parcel of air rises in the atmosphere and is not saturated, it cools according to the dry adiabatic lapse rate. This phenomenon occurs because as the air parcel ascends, it expands due to the lower atmospheric pressure at higher altitudes. During this expansion, the air performs work on its surroundings, and this process leads to a decrease in temperature. The rate at which this parcel cools is typically around 10 degrees Celsius per kilometer, which is known as the dry adiabatic lapse rate.

In contrast, options suggesting that the temperature warms or remains constant do not align with the fundamental principles of thermodynamics governing adiabatic processes. As the parcel rises and cools, it can eventually reach its dew point and become saturated, but during the initial rise while it is still unsaturated, it strictly follows the dry adiabatic lapse rate. Understanding this concept is crucial for grasping how air movement contributes to weather patterns and climate dynamics.