To understand this, we assume that this one bubble, or air parcel, retains its shape and general chraracteristics as it moves up (or down) relative to the surrounding atmospheric environment. It turns out that when air parcels do this, they actually can become warmer (or colder) than the surrounding air at the same pressure elevation.
Straightforward application of the Ideal Gas Law (Equation of State) shows that such air parcels will then be less dense (or more dense) than the surrounding air at the same elevation and will spontaneously rise (or sink). The SPONTANEOUSLY rising air parcels form the updrafts in thunderstorms.
Parcel theory has its limitations, since it is difficult to define how large or small a parcel really is and what mechanisms exist that selectively lift the small parcel and not the entire atmospheric layer. In addition, parcel theory fails to accomodate the fact that considerable entrainment of surrounding air occurs as buoyant plumes develop. However, parcel theory has been shown to be successful in explaining thunderstorm development. Hence, we will use it in this presentation.
To understand this, we assume that this one bubble, or air parcel, retains its shape and general chraracteristics as it moves up (or down) relative to the surrounding atmospheric environment. It turns out that when air parcels do this, they actually can become warmer (or colder) than the surrounding air at the same pressure elevation.Straightforward application of the Ideal Gas Law (Equation of State) shows that such air parcels will then be less dense (or more dense) than the surrounding air at the same elevation and will spontaneously rise (or sink). The SPONTANEOUSLY rising air parcels form the updrafts in thunderstorms.Parcel theory has its limitations, since it is difficult to define how large or small a parcel really is and what mechanisms exist that selectively lift the small parcel and not the entire atmospheric layer. In addition, parcel theory fails to accomodate the fact that considerable entrainment of surrounding air occurs as buoyant plumes develop. However, parcel theory has been shown to be successful in explaining thunderstorm development. Hence, we will use it in this presentation.
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