The figures to the right show the number of observations distributed over different values of the mixing coefficient (Kρ). The top figure shows Day 2 and the bottom figure shows Day 3. Let us speculate a little about the similarities and the differences between these two spectra...
Now, Kρ is the product of the turbulent velocity (square root of the turbulent energy) and the turbulent length scale. On scales longer than (~30 times!) the Kolmogorov scale dissipation is little. The turbulent energy at a given time will a later time appear at a shorter length scale, i.e. at a smaller Kρ value. So, what I am saying is that the figures to the right can be seen as spectra of TKE for length scales. So why do I not plot that instead?!