From Glossary of Meteorology
The state of a fluid that is characterized by both barotropy and piezotropy, that is, pressure and density surfaces coincide.
This condition guarantees that the fluid will remain barotropic at all future times. Example: an ideal homentropic fluid (i.e., a fluid with homogeneous potential temperature) with uniform composition.
Gill, A. E. 1982. Atmosphere–Ocean Dynamics. Academic Press, . p. 228.
Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact firstname.lastname@example.org. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.