Harmonic analysis of tidal constituents (key_ diaharm)


A module is available to compute the amplitude and phase of tidal waves. This on-line Harmonic analysis is actived with key_ diaharm. Some parameters are available in namelist namdia_harm :

- nit000_han is the first time step used for harmonic analysis

- nitend_han is the last time step used for harmonic analysis

- nstep_han is the time step frequency for harmonic analysis

- nb_ana is the number of harmonics to analyse

- tname is an array with names of tidal constituents to analyse

nit000_han and nitend_han must be between nit000 and nitend of the simulation. The restart capability is not implemented.

The Harmonic analysis solve the following equation:

$\displaystyle h_{i} - A_{0} + \sum^{nb\_ana}_{j=1}[A_{j}cos(\nu_{j}t_{j}-\phi_{j})] = e_{i}$ (11.1)

With $ A_{j}$,$ \nu_{j}$,$ \phi_{j}$, the amplitude, frequency and phase for each wave and $ e_{i}$ the error. $ h_{i}$ is the sea level for the time $ t_{i}$ and $ A_{0}$ is the mean sea level.
We can rewrite this equation:

$\displaystyle h_{i} - A_{0} + \sum^{nb\_ana}_{j=1}[C_{j}cos(\nu_{j}t_{j})+S_{j}sin(\nu_{j}t_{j})] = e_{i}$ (11.2)

with $ A_{j}=\sqrt{C^{2}_{j}+S^{2}_{j}}$ et $ \phi_{j}=arctan(S_{j}/C_{j})$.

We obtain in output $ C_{j}$ and $ S_{j}$ for each tidal wave.

Gurvan Madec and the NEMO Team
NEMO European Consortium2017-02-17