# Barotropic model

From AMS Glossary

## barotropic model

- Any of a number of model atmospheres in which some of the following conditions exist throughout the motion: coincidence of pressure and temperature surfaces; absence of vertical wind shear; absence of vertical motions; absence of horizontal velocity divergence; and conservation of the vertical component of absolute vorticity.

Barotropic models are usually divided into two classes: the nondivergent barotropic model and the divergent barotropic model (also called the shallow-water equations).

- A single-parameter, single-level atmospheric model based solely on the advection of the initial circulation field.

The simplest form of barotropic model is based on the barotropic vorticity advection equation:where ψ is the geostrophic streamfunction,**V**_{ψ}is the nondivergent wind, and*f*is the Coriolis parameter. The equation is derived by assuming that a vertical portion of the atmosphere is barotropic (i.e., density is constant on pressure surfaces) and nondivergent. Because there are no vertical variations or thermal advection processes in a barotropic model, it cannot predict the development of new weather systems.