A Theory of Non-Stationary Oceanic Ekman Layer

[摘要] In order to investigate the response of the Ekman boundary layer of the ocean to fluctuating wind stress, we solved analytically the time dependent equations of motion as an initial value problem by extending the Fredholm's solution. The frequency distribution of the time average value of the surface horizontal velocity is numerically estimated from the analytical solution. The calculated amplitude of response is compared with that due to the steady wind stress.It is shown that in general the responded amplitude of the Ekman boundary layer to the transitory wind stress is smaller than that to the steady wind stress except the case where the frequency of the forcing wind stress ω equals to the inertial frequency ƒ. For ω which is close to, but not exactly equals to zero, one would overestimate the amplitude if one averages it over a shorter time interval than the period of the forcing, 2π/ω. For ω=ƒ, the magnitude of the oscillatory velocity component increases proportionally to the square root of the time elapsed.

[学科分类] 大气科学