MAINTENANCE MECHANISM OF THE KUROSHIO FRONT

Research Project

Project/Area Number	04640421
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	気象・海洋・陸水学
Research Institution	KAGOSHIMA UNIVERSITY
Principal Investigator	ICHIKAWA Hiroshi KAGOSHIMA UNIVERSITY FACULTY OF FISHERIES ASSOCIATE PROFESSOR, 水産学部, 助教授 (60128410)
Co-Investigator(Kenkyū-buntansha)	OHNO Yuichi THE COMUNICATIONS RESEARCH LABORATORY DEPARTMENT OF EARTH ENVIRONMENT OBSERVATIO, 地球環境計測部, 郵政技官
Project Period (FY)	1992 – 1993
Project Status	Completed (Fiscal Year 1993)
Budget Amount *help	¥1,900,000 (Direct Cost: ¥1,900,000) Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000) Fiscal Year 1992: ¥1,400,000 (Direct Cost: ¥1,400,000)
Keywords	Kuroshio / Oceanic Front / Horizontal Convergence / HF Ocean Surface Radar / HFレーダ
Research Abstract	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.