MAINTENANCE MECHANISM OF THE KUROSHIO FRONT

这一为期两年的项目的目的是阐明在黑河沿岸具有重要意义的海洋锋面的维持机制。1992年10月至12月的3个月中，用高频海面雷达每隔2小时测量了屋久岛岛西南约50公里×20公里海流的时空变化。利用9月1日至12月31日屋久岛岛逐日气象资料、NOAA/AVHRR卫星12月24日红外热像资料以及9月1日至12月31日每隔两天往返鹿儿岛至那霸的渡轮所测得的海面温度时间变化资料，分析了高频雷达观测期长期大尺度变化的外部条件。根据1992年11月17日至23日海面涡度的水平辐合和垂直分量的分布及其时间变化，发现虽然水平辐合区的空间分布受潮流的影响较大，但在黑潮北缘，辐合区和散度区交替分布，空间尺度为2-6公里。25小时平均辐合度可达1.5x10；-4；S。当锋面向南移动时，水平辐散占主导地位，反之亦然。我们的观测证实了锋面涡在黑潮锋面的维持中起着重要的作用，并发现沿黑潮的辐合区并不是以狭长的带状存在，而是辐合区和散度区交替分布。

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.