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Analyzing Harmonic Data in Model Calibration for Tidal Field Flows

Explore the concept of harmonic analysis in calibrating models using data from Walnut Grove, Rio Vista, and Julian Day. Discover how individual tidal constituents influenced by sun and moon frequencies impact amplitude and phase, crucial for accurate model evaluation. Learn why precise phase shifts matter in Eulerian flux calculations and ensuring correct dispersion terms in tidal flux analysis.

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Analyzing Harmonic Data in Model Calibration for Tidal Field Flows

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  1. Harmonic Analysis –use in calibrating models Larry Smith USGS retired

  2. Data contain variability at a number of frequencies Walnut Grove 15-minute Flows Rio Vista Julian Day

  3. tidal field data decompose to… Individual constituents • caused by • sun & moon • so frequencies • are known • location on earth • influences • amplitude and • phase of • each constituent

  4. from field data A Cos(wt+P) A’ Cos(wt+P’) Model evaluation concept a Cos(wt+p) a’ Cos(wt+p’) from model calculations For a given w if we set (a=A, p=P), and run the model, does a’=A’ and p’=P’?

  5. Why does it matter?One answer comes from Eulerian flux calculations: <QC> = <Q> <C> + <Q’C’> advection + dispersion where < > is tidal mean, and Q’ = Q - <Q> etc. ~

  6. Mallard Island seaward landward

  7. Mallard Island seaward landward

  8. Net salt flux over the tidal cycle <QC> = <Q> <C> + <Q’C’> = 110 X 2.7 + (-1900) = -1600 ~ landward! A 1-hour phase shift causes the dispersion term to grow from 0 to -1900! Getting correct phase shifts is an essential part of model calibration.

  9. Particle paths are a Lagrangian calculationfor which model phases and amplitudes must be accurate….

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