56 EIGHTH PACIFIC SCIENCE CONGRESS 



Diffusion 



In 1949 T. Ichiye treated the Brownian movement of a particle of 

 water produced by a stochastic extraneous force in a field of Coriolis 

 forces, and determined the dependence of eddy diffusivity upon the 

 latitude. He compared this theoretical result with the horizontal dif- 

 fusivity determined from the distribution of conservative concentrations 

 in the ocean currents, and showed how the horizontal eddy diffusivity 

 could be determined from the drift of R.V. "Deutschland" in the Ant- 

 arctic Ocean (OM, 1, 1949). 



In 1950 Ichiye considered a statistical theory of turbulent diffu- 

 sion, discussing the diffusion from an origin by a process similar to 

 Brownian motion, and could explain the so-called scale effect postula- 

 ted by Lewis F. Richardson (KMOM, 8, 1950). He also made some re- 

 marks on Richardson's neighbor diffusion equation (OM, 2, 1950). He 

 applied this theory to the diffusion of water masses in the oceans and 

 gave a qualitative explanation on the variation of the horizontal Aus- 

 tausch coefficient in the ocean currents by developing the spectral theo- 

 ry of turbulence in case where irregular extraneous forces are in action 

 (OM, 3, 1951). Yasukazu Saito solved the problem of diffusion of sa- 

 linity in a horizontal current field, both horizontal and vertical mixing 

 being taken into account (TUFJ, 38, 1952, 182-191). 



T. Nan'niti determined the horizontal and vertical eddy diffusi- 

 vity using Montgomery's method from the actual distribution of salin- 

 ity. He obtained horizontal and vertical coefficients to be 10'^ and 10^ 

 respectively (OM, 3, 1951). From the salinity distribution on the core 

 sheet of the Subarctic Intermediate water near Japan, J. Masuzawa ob- 

 tained horizontal eddy diffusivity to be lO^-lO^ c.g.s. (KH, 2, 1951-52). 

 E. Inoue concluded this quantity has a value 10^° c.g.s., a value much 

 larger than previously knov/n (KS, 28, 1950, 420-424). 



In 1950 Ichiye treated the annual variation of the heat contents 

 at several stations in Osaka Bay as a horizontal diffusion by tidal cur- 

 rents (KMOM, 8, 1950). 



In 1952 Ichiye discussed the relation between the O2 minimum 

 layer and the motionless layer in case where both horizontal and verti- 

 cal diffusions occur, and showed theoretically how the depth of O2 mi- 

 nimum layer varies as the distance from the source increases when there 

 is biological dissipation. He determined the schematic distribution of 

 oxygen in the sea when the processes of dissipation, supply and diffu- 

 sion are going on simultaneously (US, 29, 1952). 



On September 17, 1952, a new submarine volcano was observed 

 erupting from the Pacific floor south of Japan. This submarine erup- 

 tion ejected a great deal of pumice stones afloat on the sea surface. 



