Tide forecast

Under tide prediction (English tide-prediction ) is the prediction of the course of the tide and the tidal currents .

history

The tide forecast can be traced back a few centuries and has been gradually improved with new knowledge of the tides . Initially, there were simple tables with collected information about the times of day floods, in the further development tide tables with information about heights and times of the high and low tide for a reference location as well as differential values for the connection location to be attached. The tide tables published in the United Kingdom by John Flamsteed from 1664 onwards remained authoritative for nearly 150 years. Sir John Lubbock , 3rd Baronet (born March 26, 1803 † June 21, 1865) developed tables using the nonharmonic method . In this new method, he describes the inequality of the tides as a result of the influences of the moon phase as well as the declination and parallax of the moon and sun and how they can also be used to determine the entry times of high and low water. For the North Sea , as a distinct shelf sea , this method gave acceptable results. However, it was restricted to certain sea areas in which half-day tides with two high and two low tides occurred within a mean lunar day of 24 hours and 50 minutes.

In 1868 Lord Kelvin took a completely different approach to studying the problem of tidal forecasting. Lord Kelvin divided the tidal curves reflecting the course of the tide into a series of harmonic oscillations according to the astronomical causes , the periods of which were derived from the theory of the movements of the earth, moon and sun to one another. He determined the amplitudes and phases of the individual harmonic oscillations or partial tides by observing the tides over a longer period of time and created mean values ​​for both quantities. Using known astronomical parameters and their modification, he was able to make predictions for the respective year. This prediction, also known as the harmonic method , supplements the gaps in the nonharmonic method . However, it fails in shallow water areas despite the additional partial tides introduced as obertides and their repeated expansion by combining the latter as composite tides. This is why the Federal Maritime and Hydrographic Agency has been calculating the tides for the German Bight and its river basins since 1954 using the method known as the Harmonic Representation of Inequalities . At certain intervals, a new determination of the calculated values ​​is necessary due to changes in the coastline in the coastal apron and after human intervention through engineering structures such as harbors and jetties.

A large number of hydrographic offices around the world publish tide tables with detailed forecasts for hundreds of reference locations and thousands of connection locations on all coasts of the world.

See also

• Tide calendar
• Tide calculation

literature

• K. Schwitalla, U. Scharnow: Lexicon of seafaring . 5th edition. transpress VEB Verlag for Transport, Berlin 1988, ISBN 3-344-00190-6 .
• Tide calendar 2010 . Federal Maritime and Hydrographic Agency, 2009, ISBN 978-3-89871-927-8 .
• U. Scharnow: seamanship 3rd ship and maneuvers . 3. Edition. transpress Verlag, Berlin 1987, ISBN 3-344-00151-5 .

References and comments

1. ↑ Sylvin H. Müller-Navarra: Tide forecasts with the harmonic representation of inequalities . Reports of the Federal Maritime and Hydrographic Agency No. 50/2013, Hamburg and Rostock, 2013, p. 5. ( Memento of the original dated January 9, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.