Document Type

Article

Publication Date

5-1990

Publication Title

Journal of Physical Oceanography

ISSN

0022-3670

Volume

20

Issue/No.

5

First Page

617

Last Page

628

Abstract

Measurements made in the Equatorial Atlantic during the 35th cruise of the R/V Akademic Vernadsky using a free-rising profiler and drifters revealed a near-surface slippery layer of the ocean arising due to daytime solar heating. The solar heating warms and stabilizes the surface layer of the ocean. This suppresses turbulent exchange and limits the penetration depth of the wind-induced turbulent mixing. The heated near-surface layer is then slipping over the underlying water practically without friction. At daytime warming of 1°C the resistance coefficient in the upper 5-m ocean, Cu = (U*Us)2 became smaller by a factor of 25–30 as compared with the case of neutral stratification. The effect of slipping results in forming a daytime near-surface current. At low wind speed the velocity of this current was observed to achieve 19 cm s−1. A simple one-dimensional integral model reproduces the main diurnal variation of the temperature and the current velocity in the near-surface layer of the ocean.

For daytime the experimental data suggest the existence of a self-regulating state of the diurnal thermocline, which predicts linear temperature and velocity profiles and an equilibrium value of the bulk Richardson number. This provides simple relations coupling the temperature and velocity differences and the thickness of thermocline. An estimation of the upper velocity limit of the daytime near-surface current is equal to 29 cm s−1.

Comments

©1990 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act September 2010 Page 2 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108, as revised by P.L. 94-553) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a web site or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. Additional details are provided in the AMS Copyright Policy, available on the AMS Web site located at (http://www.ametsoc.org/) or from the AMS at 617-227-2425 or copyrights@ametsoc.org.

ORCID ID

0000-0001-6519-1547

DOI

10.1175/1520-0485(1990)020<0617:SNSLOT>2.0.CO;2

Peer Reviewed

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