Ekman layer

From Glossary of Meteorology



Ekman layer

(Sometimes called spiral layer.) A hypothetical layer of air at the bottom of a statically neutral atmosphere surrounding a rotating planet, where surface friction and small eddies (local turbulence) cause ageostrophic, cross-isobaric winds.

The spiral shape of a hodograph of this flow is called an Ekman spiral. The Ekman layer is not observed in the earth's atmosphere because of the existence of large eddies (nonlocal turbulence) creating a mixed layer, and because the earth's troposphere is statically stable on average, causing a thermodynamic cap to the boundary layer rather than a dynamic cap at a theoretical Ekman layer depth of 20 u*/f, where u* is the friction velocity and f is the Coriolis parameter.
Compare atmospheric boundary layer.


Copyright 2024 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact [email protected]. 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.