Equilibrium
From Glossary of Meteorology
equilibrium
- In mechanics, a state in which the vector sum of all forces, that is, the acceleration vector, is zero.
In hydrodynamics, it is usually further required that a steady state exist throughout the atmospheric or fluid model. The equilibrium may be stable or unstable with respect to displacements therefrom.
See also hydrostatic equilibrium, geostrophic equilibrium, instability.
- In thermodynamics, any state of a system that would not undergo change if the system were to be isolated.
Processes in an isolated system not in equilibrium are irreversible and always in the direction of equilibrium.
