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We next look at the effects of interpolation grid resolution: Again plotting E(k)/E_0(k). Observations:
The HO algorithm is quite good enough (no significant rolloff at wave number 200) at a resolution of 1537x3072 with slight rolloff visible at 1025x2048.
The bilin algorithm requires more than twice as much resolution to match the results of highorder.
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The spectra above from single snaphots have a lot of noise which can be removed by time averaging. We next analyze how much averaging is necessary from an aqua planet NE256 simulation with 1 month of daily snapshots. The legend indicates how many snapshots were used when averaging E(k). Left plot is with daily snapshots, right plot is with 3h snapshots. With 1 month of averaging, the data is still a touch noisy, with either daily or 3h output. The 3h data is only slightly less noisy than daily (comparing 233 snapshots of 3h data to 28 snapshots of daily data). 2 months of 12h data would probably be sufficient. In the plots below, each curves are all shifted downward so they would not be plotted on top of each other.
Software needed
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