What term describes the difference between the existing temperature at 500 millibars and the temperature of a lifted air parcel?

The term that describes the difference between the existing temperature at 500 millibars and the temperature of a lifted air parcel is known as the lifted index. This index is a measure used in meteorology to assess the stability of an air mass.

When an air parcel is lifted, it cools at a certain rate due to the adiabatic process. By comparing the temperature of this lifted air parcel to the temperature of the surrounding environment at a specific pressure level (such as 500 millibars), the lifted index quantifies how buoyant or stable the air mass is. A negative lifted index indicates that the lifted parcel is warmer than the environment, suggesting that it is likely to rise further, leading to instability and potential convection. Conversely, a positive lifted index indicates more stable conditions, as the air parcel is cooler than the surrounding environment and is less likely to rise.

Understanding the lifted index is crucial for predicting weather phenomena such as thunderstorms and convection processes, making it a key concept in atmospheric studies.