抄録
Based on Kolomogoroff's similarity hypothesis of locally isotropic turbulence, the correlation coefficient Rt of the velocity fluctuations at time points t0 and t+t0 is written as follows: Rt=1-(t/T0)2/3 . (1) where T0 denotes the passing duration of the largest turbulent element which passes through the measuring point. Assuming that the correlation coefficient (Rt)w, which is calculated from the vertical velocity fluctuations w' measured in the air layer near the ground, is expressed by the formula (1), the dependence of T0 on the height of observation z and on the mean velocity u is obtained experimentally. From photographic records of vertical velocity fluctuations w' measured in the adiabatic atmosphere over level snow surfaces, Rt is calculated and is found to be well expressed by (1) in the range of small t's. It is concluded from the experimental data that T0 is proportional to z. _??_ Consequently, the spectrum of turbulent energy in the space of wave-number k is expressed by (k/k0)-5/3, where k0 is inversely proportional to z.
