The Coherent Structure inside the Oceanic Turbulence 
around Japan-Islands-Chain 
Tsukasa Nishimura*, Tomonao Kobayashi*, Sotaro Tanaka**, 
Toshiro Sugimura**, Yuji Hatakeyama*** 
Science University of Tokyo, 2641 Yamazaki, Noda-shi, 278, Japan* 
Remote Sensing Technology Center of Japan, 1-9-9 Roppongi, Minatoku, 106, Japan** 
Asia Air Survey Co. Ltd., 5-42-32 Asahi-cho, Atsugi-shi, 243, Japan*** 
Abstract 
Coastal and marine engineerings around Japan-Islands-Chain are hydrodynamically 
influenced by the oceanic turbulence due to the Kuroshio, the western boundary current in the 
North-Pacific-Ocean. The process is dominated by the mesoscale eddy structure, the coherence of 
which is enhanced so much by the specific tectonic and atmospheric settings. An example is the 
yellowtail fixed net fishery, the engineering of which has been sophisticated through these 400 
years. In this presentation, some NOAA/AVHRR-based flow visualization and instantaneous 
turbulence measurements are exhibited, and the approaching method is discussed by comparing to 
the Gulf-Stream or refering to the old yellowtail fishermen's knowledge base on air and sea. 
1. Geometric and kinematic perspectives gained through NOAA/AVHRR 
1.1 Scale estimation, sampling strategy and coherent structure concept 
As the oceanic turbulence around Japan-Islands-Chain links so much intimately to the 
Kuroshio, a large amount of oceanographic surveys have been accumulated in this half a century 
although implicitly; e.g. statistical analyses of hydrographic data (Kawabe 1980), mooring or 
drifting buoy measurements (Taira et al. 1981), and microwave altimetry of sea surface dynamic 
topography (Ichikawa, et al. 1992). Through these approaches, however, the hydrodynamics of 
coherent structure hasn't yet been explicitly uncovered, owing to some mismatch in the scale 
estimation, data sampling strategy and in the basic viewpoints to the turbulence itself. 
Early in the 1980s, we started a campaign introducing the coherent structure concept. 
Energy containing components, mesoscale eddies, were focused on. Representative space and time 
scales were 100 km and days. Polar orbiting visible and infrared image sensor NOAA/AVHRR was 
employed as a measuring tool for the instantaneous turbulence field extending over 1,000km. 
Space, time and radiometric resolutions are 1.1 km at nadir, 6 hours, and 0.1 K respectively. 
1.2 Geometric correction and radiometric enhancements 
Figure 1(a) shows a gray-scale enhanced NOAA/AVHRR infrared image, 0344, 19 April 
1993. Objective of this flow visualization was to exhibit a whole perspective of instantaneous 
turbulence as well as detailed features of each mesoscale eddy on a single NOAA image. To tune 
up the technique, some data processings were devised in geometric and radiometric domains. 
Applying the oblique conformal secant conic projection, AVHRR data were geometrically 
corrected into the 1/3,000,000 topographic chart published from Geographical Institute of Japan 
(Tanaka et al. 1983). Through this distance conserving mapping, the data were resampled to assign 
each image pixel to a 1km square unit area. In the process, some pieces of GCPs (Ground Control