a a DIR 
A PS 
3. LANDSAT REMOTE SENSING OF THE LARGE SCALE TIDAL VORTICES 
Large scale tidal flow field was surveyed through multi level remote 
sensing using Landsat and airplanes at higher altitude. Fig. 8 shows the rela- 
tionship between the large scale flow field and the small scale one aforementi- 
oned. Space and time scales of each of the flow fields are also shown in the 
figure. The scales of the large scale flow field are one order higher than 
those of the small scale one. When one observe the small scale tidal vortices 
from the large scale view point, then, one will observe the large scale tidal 
vortices are being formed after the amalgamation process among the small scale 
tidal vortices. 
Landsat MSS data were analyzed to reveal the formation process of the 
large scale tidal vortices, their kinematics and hydrodynamic roles in the tidal 
exchange through the strait between the water masses in the Kii Channel and in 
the Harima Sea. Images of D in Fig. 9 were gained after the digital 
enhancement and color slice analysis. Tidal current at the data acquisition 
time was just under the following conditions. 
Gy : northward tidal current at the maximum speed. 
(2 : slack from northward current to southward. 
(3) : southward current at the maximum speed. 
It is very interesting that each of them has the typical phase of 7/2, 7C and 
37C/2, respectively. On each imagery, a symmetric water mass can be found to be 
li formed in the Harima Sea. On Fig. 10, each stage of the formation process of 
1i the large scale water mass is superimposed in a sheet, on which one can under- 
n stand the aspects of its growth and motion. The most interesting fact is that 
I the water mass indicated as is penetrating far into the Harima Sea beyond 
UN the position of the water mass , while the surrounding water in the Harima 
In Sea has has changed its flow direction to the south at the time of the observa- 
tion of the water mass © 
The formation of the large scale water mass and its motion can be 
explained schematically in Fig. 11 based on the coherent structure theory. In 
large scale 
large scale 
p--------2-2--2-2-2---2----------------------- A 
\ 
  
(TIDAL VELOCITY) 
  
t+12 hour 
t ^. 
small 
scale CRIME! 
  
  
  
(a) space scale (b) time scale 
Fig. 8. Space and time scale of the tidal flow field. 
740 
  
ae ES