| 释义 |
Ekman, n.|ˈɛkmən|
The name of V. W. Ekman (1874–1954), Swedish oceanographer, used attrib. to designate concepts and phenomena associated with his work, as Ekman current meter, a device for measuring the speed and direction of seawater during a timed interval by means of a propeller with a revolution-counter and a vane that periodically releases a small weight into one of a set of sectorial compartments; Ekman layer, the layer of ocean (extending from the surface to the foot of the Ekman spiral) within which the wind has an effect upon the current; a layer in any fluid affected by friction at a boundary; Ekman number, the dimensionless quantity ν/l2ωρ , where ν is the kinematic viscosity, l a length, ω angular velocity, and ρ mass-density; Ekman spiral [propounded by Ekman in Nyt Magazin for Naturvidenskaberne (1902) B. XL. 1–27], a spiral that ideally represents both the increasing angular difference between the wind direction and a wind-induced ocean current, and the decreasing speed of the current, at increasing depths; a similar spiral ideally representing wind direction and speed between the ground and the height at which its frictional effect on the geostrophic wind disappears; Ekman transport, the overall movement of ocean water attributable to the frictional effect of wind at different depths.
1942H. Sverdrup Oceanogr. iii. 46 Owing to its simplicity and reliability, the Ekman current meter is widely used. Ibid. vii. 125 (caption) Schematic representation of a wind current in deep water, showing the decrease in velocity and change in direction at regular intervals of depth (the Ekman spiral). 1945F. A. Berry et al. Handbk. Meteorol. vi. 454 If the Ekman spiral is used to analyze experimentally obtained wind distributions, the magnitudes of the exchange coefficient and the viscous stresses can be obtained. 1957Deep-Sea Res. IV. 154 Non-uniformity of the wind stress over the ocean causes a convergence or divergence within the Ekman layer. 1963G. L. Pickard Descriptive Physical Oceanogr. vi. 77 Perhaps the most used Eulerian instrument is the Ekman current meter. 1967R. W. Fairbridge Encycl. Atmospheric Sci. 705/1 The vectorial water transport by wind drift integrated down to the bottom of the drift layer (‘Ekman transport’) is directed 90° to the right of the wind direction. Ibid. 838/2 An inverted form which has been used is the Ekman number. 1970Sci. Amer. Jan. 117/1 Thus the wind in the southern half of our square basin representing the North Atlantic transports water to the north in the thin Ekman layer. 1972M. G. Gross Oceanogr. viii. 226 In coastal regions, the Ekman transport of waters can cause upwelling. 1978Sci. Amer. Aug. 30/1 (caption) Gas movement in a centrifuge... Thin gas-containing zones known as Ekman layers, each only a fraction of a millimeter thick, are formed at the extremities of the Stewartson layer, where the circulatory flow changes direction. 1979Ibid. Feb. 95/3 In fluid dynamics the ratio of the viscous forces to the Coriolis force is called the Ekman number. 1982Clayton & Bishop Mech. Marine Vehicles vii. 344 This veering effect is the result of the Ekman Spiral in the aerodynamic boundary layer. |