2.7.4 - The role of the Sun in the tides.
On the tides, it is the Moon to play the larger role.
However, for the most part of the days, it is the Sun which determines what I call the daily structure of the tidal waves.
Intervals between two successive tidal waves.
At Venice, for at least 280 days in one year, it is the Sun declination which determines two main features: the longer interval between two successive tidal waves, and, consequently, in which part of the day the lowest water level takes place.
Always, except near the equinoxes.
The Sun determines the aforesaid features, except during the days near one of the equinoxes, when its declination relative to the equatorial plane is zero, or negligeable.
Between april and august.
It is here considered the period between april and august, when the Sun presents enough degrees of north declination.
Near midday, the Sun passes over the local meridian, and its spatiole comes early.
Instead, near midnight, the Sun passes over the opposite meridian, and its spatiole comes late.
The longer interval between two sun spatioles.
The centre of the longer interval between sun spatioles will be the one between the midday spatiole and the midnight one; thus, late in the afternoon.
Then, after having taken into account the contribution of the moon spatioles, and added the delay of the tidal wave valid for Venice (more than ten hours), one may forecast the time of the lowest water level for the day; anyway, it will be between midnight and the early morning hours.
An example: june 2007.
Between october and february.
It is here considered the period between october and february, when the Sun presents enough degrees of south declination.
Consequently, the midday passage of the Sun spatiole will take place late; while the midnight passage will come early.
Relative to the pattern of the period between april and august, everything is displaced by 12 hours. The lowest daily water level, at Venice, will take place during the afternoon.