Improving the estimate of wind energy input into the Ekman layer within the Antarctic Circumpolar Current
- PDF / 2,400,179 Bytes
- 9 Pages / 595.276 x 841.89 pts (A4) Page_size
- 35 Downloads / 145 Views
Improving the estimate of wind energy input into the Ekman layer within the Antarctic Circumpolar Current ZHANG Yuming1 , WU Kejian1∗ , ZHANG Xiaoshuang3 , BI Fan1 , SONG Zhaoyang1 , LIU Shouhua2 1
Physical Oceanography Laboratory, Ocean University of China, Qingdao 266100, China National Marine Data & Information Service, Tianjin 300171, China 3 Key Laboratory of Marine Environmental Information Technology, State Oceanic Administration, National Marine Data and Information Service, Tianjin 300171, China 2
Received 27 June 2011; accepted 8 May 2012 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2013
Abstract Based on the data and method offered by Liu et al. (2009), the direct wind and Stokes drift-induced energy inputs into the Ekman layer within the Antarctic Circumpolar Current (ACC) area are reestimated since the results of the former have been proved to be underestimated. And the result shows that the total rate of energy input into the Ekman-Stokes layer within the ACC area is 852.41 GW, including 649.75 GW of direct wind energy input (76%) and 202.66 GW of Stoke drift-induced energy input (24%). Total increased energy input, due to wave-induced Coriolis-Stokes forcing added to the classical Ekman model, is 52.05 GW, accounting for 6.5% of the wind energy input into the classical Ekman layer. The long-term variability of direct wind and Stokes drift-induced energy inputs into the Ekman layer within the ACC is also investigated, and the result shows that the Stokes drift hinders the decadal increasing trend of direct wind energy input. Meanwhile, there is a period of 4–5 a in the energy spectrums, as same as the Antarctic circumpolar wave. Key words: energy input, Ekman-Stokes layer, Coriolis-Stokes forcing, Antarctic Circumpolar Current Citation: Zhang Yuming, Wu Kejian, Zhang Xiaoshuang, Bi Fan, Song Zhaoyang, Liu Shouhua. 2013. Improving the estimate of wind energy input into the Ekman layer within the Antarctic Circumpolar Current. Acta Oceanologica Sinica, 32(3): 19–27, doi: 10.1007/s13131-013-0284-6
1 Introduction Recent studies show that the surface waves would have influences on the wind energy input into the Ekman layer (Liu et al., 2007; hereinafter L07), because it affects the current profiles, via the Coriolis-Stokes force (Levis and Belcher, 2004; Polton et al., 2005; Hasselmann, 1970; Xu and Bowen, 1994; Sun et al., 2004), and this energy input depends not only on the wind stress vector but also on the current profiles. In an ocean of deep and unlimited horizontal extent, the coupled potential energy term can be neglected for the mean motion without horizontal pressure gradients, horizontal mean velocity gradients, or sea level elevations. Incorporating the Coriolis-Stokes force into the classical Ekman model and assuming a constant vertical diffusivity, L07 deduced the waveaverage energy balance equation for the Ekman-Stokes layer as (Eq. (6) in L07)
D = ρw
∂ U 2 Az dz ; ∂z −∞ 0
in which E , E w , E S and D respectively represent the total kinetic
Data Loading...
