# Perturbation

From Glossary of Meteorology

Revision as of 14:50, 20 February 2012 by imported>Perlwikibot

## perturbation

Any departure introduced into an assumed steady state of a system.

The magnitude is often assumed to be small so that product terms in the dependent variables may be neglected; the term "perturbation" is therefore sometimes used as synonymous with "small perturbation." The perturbation may be concentrated at a point or in a finite volume of space; it may be a wave (sine or cosine function); in the case of a rotating system, it may be symmetric about the axis of rotation; or it may be a displacement by the parcel method. The mathematical work in an instability problem may be facilitated by the perturbation technique, whether or not the equations are linearized. In synoptic meteorology, this term is used for any departure from zonal flow within the major zonal currents of the atmosphere. It is especially applied to the wavelike disturbances within the tropical easterlies.

*See*easterly wave;*compare*disturbance.

Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact permissions@ametsoc.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.