A barotropic atmosphere is one in which the density depends only on the pressure, so that isobaric surfaces are also surfaces of constant density. The isobaric surfaces will also be isothermal, hence (from the thermal wind equation) the geostrophic wind is independent of height. Hence the motions of a rotating barotropic fluid are strongly constrained.

Contrast baroclinic.

References

• James R Holton, An introduction to dynamic meteorology, ISBN 0-12-354355-X, 3rd edition, p77.