Fast Wind-Induced Migration of Leddies in the South China Sea

作者：Nof Doron^*; Jia Yinglai; Chassignet Eric; Bozec Alexandra

来源：Journal of Physical Oceanography, 2011, 41(9): 1683-1693.

DOI：10.1175/2011JPO4530.1

Eddies off the Strait of Luzon (termed here as "Leddies," analogous to "Teddies" originating from the Indonesian Throughflow) are formed rapidly and migrate swiftly. Their migration rate (similar to 10-20 cm s(-1)) is an order of magnitude faster than that of most eddies of the same scale (similar to 1 cm s(-1)). On the basis of observations, it has been suggested earlier that the rapid generation process is due to the southeast monsoon.
Here, the authors place this earlier suggestion on a more solid ground by developing both analytical and process-oriented numerical models. Because the eddies are formed by the injection of foreign, lighter Kuroshio water into the South China Sea (SCS), the eddies are modeled as lenses: that is, "bullets" that completely encapsulate the mass anomaly associated with them. It turns out that the rings migrate at an angle a (between 0 degrees and 90 degrees) to the right of the wind direction {i.e., tan(-1)[(2 - gamma)f(2) R/8g'C(D)], where in conventional notation gamma is the vorticity, R the eddy radius, and C(D) the interfacial friction coefficient along the lower interface of the lens}. Their fast migration speed is given by 2(tau(S)/rho(W))(sin alpha)/fH, where tau(S) is the wind stress on the surface, rho(w) the water density, and H is the maximum eddy depth. With high interfacial drag (i.e., large C(D)), the rings move relatively slowly (but still a lot faster than Rossby waves) in the wind direction, whereas with low drag they move fast at 90 degrees to the right. These analytically predicted values are in good agreement with isopycnic numerical simulations.

• 出版日期2011-9
• 单位中国海洋大学