  Kolmogorov's theory for turbulence in 1941 is based on a hypothesis that
small-scale statistics are uniquely determined by the kinematic viscosity and
the mean rate of energy dissipation. Landau remarked that the local rate of
energy dissipation should fluctuate in space over large scales and hence should
affect small-scale statistics. Experimentally, we confirm the significance of
this large-scale fluctuation, which is comparable to the mean rate of energy
dissipation at the typical scale for energy-containing eddies. The significance
is independent of the Reynolds number and the configuration for turbulence
production. With an increase of scale r above the scale of largest
energy-containing eddies, the fluctuation becomes to have the scaling r^-1/2
and becomes close to Gaussian. We also confirm that the large-scale fluctuation
affects small-scale statistics.
