Department of Oceanography, University of Hawaii at Manoa, 1000 Pope Road, Honolulu, Hawaii 96822, USA.
Global Environment and Marine Department, Japan Meteorological Agency, 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan.
Nat Commun. 2017 Jan 9;8:14055. doi: 10.1038/ncomms14055.
With radar interferometry, the next-generation Surface Water and Ocean Topography satellite mission will improve the measured sea surface height resolution down to 15 km, allowing us to investigate for the first time the global upper ocean variability at the submesoscale range. Here, by analysing shipboard Acoustic Doppler Current Profiler measurements along 137°E in the northwest Pacific of 2004-2016, we show that the observed upper ocean velocities are comprised of balanced geostrophic flows and unbalanced internal waves. The transition length scale, L, separating these two motions, is found to depend strongly on the energy level of local mesoscale eddy variability. In the eddy-abundant western boundary current region of Kuroshio, L can be shorter than 15 km, whereas L exceeds 200 km along the path of relatively stable North Equatorial Current. Judicious separation between the geostrophic and internal wave signals represents both a challenge and an opportunity for the Surface Water and Ocean Topography mission.
利用雷达干涉测量技术，下一代的地表水和海洋地形卫星任务将把测量的海平面高度分辨率提高到 15 公里，使我们首次能够在次中尺度范围内调查全球上层海洋的可变性。在这里，通过分析 2004 年至 2016 年期间沿 137°E 在西北太平洋的船舶声学多普勒海流剖面仪测量数据，我们发现观测到的上层海洋速度由平衡的地转流和不平衡的内波组成。将这两种运动分开的过渡长度尺度 L 强烈依赖于局部中尺度涡旋变化的能量水平。在黑潮西部边界流的涡旋丰富区域，L 可以短于 15 公里，而在相对稳定的北赤道流路径上，L 超过 200 公里。明智地分离地转流和内波信号，这既是地表水和海洋地形任务的挑战，也是机遇。
