Forward-difference

For the forward-difference scheme

1. start with $n$ being the lowest number bin of the range over which the structure function is to be evaluated (number of bins in range must exceed $n_{\text{max}}$
   1. start with $\delta =1$
   2. compute the second order forward-difference structure function $D(n,\delta )$ as the segment mean of the square of the velocity difference between the bin $n$ and bin $n+\delta$:
      
      $D(n,\delta )=⟨[v^{\prime }(n,t)-v^{\prime }(n+\delta ,t){]}^2⟩$
      
      where the angled brackets indicate the mean across all $t$ for the data segment yielding a velocity difference after the application of the Level 1 QC criteria
   3. increment $\delta$ and repeat steps until $\delta =n_{\text{rmax}}$ or $n+\delta$ exceeds the last bin of the range over which the structure function is to be evaluated
2. increment $n$ and repeat steps until $n+1$ is the last bin of the range over which the structure function is to be evaluated

See example forward-difference calculation for more detail regarding the calculation

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