The Diffusisn Coefficient in Omura and Sasebo Bay

In this paper, the diffusion cloud method by dyes and the velocity correlation method are used to calculate the diffusion coefficients in Omura and Sasebo Bay. In case of the dyes, Uranine is very cheap for dyes, clear green color, and keeps clear clouds for about two hours in a sea. Accordingly we can trace easily edges of the clouds by boats. When we calculated the increment ratio of the cloud area, we used two different ways. They are instant gradiant (⊿A/⊿T) and mean gradiant (A/T). In mean gradiant way, the gradiant of diffusion coefficient was smaller than that of the rule of 4/3 (by Richardson), and the diffusion coefficients were 1.4×105 cm2/sec in Omura Bay and 1.6×105cm2/sec in Sasebo Bay at 900m-scale. When we apply the instant gradiant way, we must be carefull to measure the area of the dyes clouds. The gradiant of the diffusion coefficient by the velocity correlation method was smallest among the those we applied, but the value was greater than the other during about 2-3 hours. The diffusion coefficients of the correlation and the dyes methods were same 2.4×104cm2/sec at near 1 hour time-scale