基于卫星测高交叉点的海洋表面地转流速度

在流体静力平衡状态下,海洋Coriolis力和压力梯度平衡就形成地转流,世界上大多数海流都近似为地转流.本文利用卫星测高交叉点方法计算海洋表面地转流速度,分析了利用测高交叉点计算地转流速度的不确定性,上升和下降弧段的海面倾斜在分辨率50 km上可以达到10^-7量级,才可能获得优于10 cm/s的地转流速度.在低纬度或者纬度接近卫星轨道倾角的地区,由交叉点方法计算的地转流速度精度低于中纬度地区.以中国台湾东部黑潮为试验区,利用最新的中国台湾周边海域大地水准面模型参考场计算高精度的大地水准面高,利用TOPEX/Poseidon和Jason-1的GDR数据(2002~2005年)计算海面高,然后计算交叉点的动力高,确定交叉点的地转流速度,结果与中国台湾NCOR(National Center for Ocean Research)的流速基本一致.

Oceanic surface geostrophic velocities determined with satellite altimetric crossover method

If the Coriolis force is balanced by the pressure gradient in the hydrostatic equilibrium, the ocean current is referred to as the geostrophic current. Most ocean currents worldwide are approximately geostrophic currents. The surface geostrophic velocity is calculated with the satellite altimetric crossover method in this paper. The uncertainties of geostrophic velocity determined from satellite altimetric crossover data are analyzed. If the accuracy of the sea surface slope along the ascending or descending track of altimetric satellite is up to the 10^-7 level with 50 km of resolution, the geostrophic velocity will have an accuracy of better than 10 cm/s. In the areas of low latitude or near the altimetric satellite orbital inclination, the uncertainty of geostrophic velocity determined with the crossover method will be much bigger than that in the low-/mid-latitude areas. The Kuroshio area east of Taiwan, China is selected as a testing region. A highly accurate and up-to-date geoidal model which is determined using the combined data from the ground-based gravimetry, ship-borne gravimetry, air-borne gravimetry and satellite altimetry, is selected as the reference geoid. Sea surface heights from the geophysical data records of TOPEX/Poseidon and Jason-1 from 2002 to 2005 are used to compute highly accurate dynamic heights at three crossover points. Geostrophic velocities are then derived at these crossover points and are basically identical to the current velocities provided by the National Center for Ocean Research, Taiwan, China.