## TASK 3. ANALYSIS OF OBSERVATIONS

##### Objective:

To corroborate the following hypotheses:

- Fortnightly switching in the residual flow direction differs with the along-estuary distribution of the density field.
- The internal tidal Froude number (Fr0, see below)) will change along the estuary and diagnose the main flow drivers (see below).

##### Expected results

- Distinct structure of residual flows across the channel on neap and spring tides.
- Fortnightly variability of the subtidal structures along the estuary.
- Along-estuary density gradients.
- Applicability of Fr0 as a diagnostic for hydrodynamic switching.

##### Internal tidal Froude number Fr0:

The internal tidal Froude number, Fr0, compares the tidal stress to the baroclinic pressure gradient. It is defined from the tidally-averaged momentum equation:

Fr_{0}^{2} = V_{0}^{2} / (g’H )

where V0 is the along estuary tidal current amplitude (in m/s), g’ is the reduced gravity (m/s2) and H is the water depth (m).