Definition
In meteorology, a small, imaginary volume of air treated as a single unit for the purpose of analyzing how it behaves as it rises, sinks, expands, cools, or warms within the surrounding atmosphere.
Plain English
A made-up small 'blob' of air that weather experts follow to see what happens to it as it moves up or down through the sky.
Context Anchor
Seen in weather discussions about stability, cloud formation, rising air, and thunderstorm development.
Derivation
From the Old French parcelle, meaning 'a small part' or 'small piece.' In meteorology it keeps that sense -- a small piece of the atmosphere considered on its own.
Why Pilots Care
Parcel theory explains why air rises or sinks, directly affecting turbulence, cloud build-up, and thunderstorm risk.
Grounding Statement
Picture a balloon-sized bubble of air rising off a sun-warmed field -- that bubble, treated as a single unit, is a parcel.
Intuition Check
Do not think of a parcel as a package or box. In weather, it means a small portion of air that is followed in an explanation.
Example Sentence 1
As the parcel of air rose, it cooled and its moisture condensed into a cumulus cloud.
Example Sentence 2
If the parcel stays warmer than the surrounding air, the atmosphere is unstable and thunderstorms may develop.