MAINTENANCE MECHANISM OF THE KUROSHIO FRONT

这个为期两年的项目的目标是阐明在黑河沿岸重要的海洋锋的维持机制。1992年10月至12月，利用高频海面雷达每隔2 h测量屋久岛西南约50 km x 20 km海域的海流时空变化。利用9月1日至12月31日屋久岛日气象资料、12月24日NOAA/AVHRR卫星红外热像图，以及9月1日至12月31日鹿儿岛至那霸轮渡每隔两天测得的海温时间变化，对高频雷达观测期的长期大尺度变化外部条件进行了考察。1992年11月17 ~ 23日海面涡度水平辐合和垂直分量的分布及其时间变化表明，水平辐合带的空间分布受潮流影响较大，但辐合带和辐散带在黑潮北缘以2 ~ 6 km的空间尺度交替分布。25小时平均辐合达到1.5 × 10^<-4> s^<-1>。锋面向南移动时，水平辐散占主导地位，反之亦然。观测结果证实了锋面涡对黑潮锋面的维持起着重要作用，并发现辐合带不是沿黑潮沿狭长带存在，而是辐合带和辐散带交替分布。

The objective of this two-year period project is to elucidate the maintenance mechanism of the oceanic front which is significant in the coastal side of the Kurosio. The spatial and temporal variation of current in the area of ca. 50 km x 20 km southwest of the Yakushima Island was measured by HF ocean surface radar every two hours during three mnonths from October to December of 1992. The daily meteorological data at the Yakushima Island from september 1 to December 31, the satellite infrared thermal image on December 24 obtained by NOAA/AVHRR, and temporal change of sea surface temperature measured by ferry liner running between Kagoshima and Naha every two days from September 1 to December 31 were utilized for examining the external conditions of the HF radar observation period in the long term and large scale variation. From the distributions of horizontal convergence and vertical component of vorticity at the sea surface and their temporal change from 17 to 23 of November, 1992, it was found that while the spatial distribution of horizontal convergence zone is largely affected by tidal current, convergence zone and divergence zone distribute alternatively to each other along the northern edge of the Kuroshio with spatial scale of 2 - 6 km. The 25-hour mean of convergence reaches up to 1.5 x 10^<-4> s^<-1>. The horizontal divergence dominates when the front is moving towards south and vice versa. It was confirmed by our observation that the frontal eddy plays an important role in the maintenance of the Kuroshio front, and found that the convergence zone does not exist as a long and narrow band along the Kuroshio, but convergence and divergence zones distribute alternatively to each other.