Spring Tide in Hong Kong
Spring Tide in Hong Kong (20 January 2005)
|
A Spring Tide occurred in Hong Kong on January 12, 2005. According to the Hong Kong Observatory's tidal records at the Tai Po Kau tide gauge station, the highest sea level was 2.94 metres above Chart Datum on that day. In the past 10 years (1995 - 2004), there were three occasions during which the sea level at Tai Po Kau in January was higher than this occasion, with the highest of 3.13 metres in 1995.
In general, there are two high tides and two low tides each day. Tidal variations are mainly caused by the gravitational attractions of the Moon and the Sun. Near New Moon or Full Moon each month, the Earth, Moon and Sun are aligned along a straight line and the sea-level rise and fall will have a larger range. This is called a Spring Tide. During First and Last Quarter Moon, the Earth, Moon and Sun are at right angles to each other. The rise and fall of the sea level will have a smaller range. This is called a Neap Tide. Since the elliptical orbits of the Moon and the Earth and the tilt of the Earth's rotation axis also affect the forces exerted by the Moon and the Sun on the Earth, the highest and lowest sea levels associated with Spring Tide are different from month to month.
Higher Spring Tides usually fall in the months of June and July as well as December and January each year. The higher sea level associated with a Spring Tide may cause minor flooding to low-lying areas while the lower sea level may affect the berthing of ferries. A rather large Spring Tide occurred on July 4, 2004. On that occasion, the lowest sea level recorded in Victoria Harbour was 0.07 metre below Chart Datum and a few ferries experienced difficulty while berthing.
According to the observatory's tidal predictions, Spring Tides that may have larger tidal ranges will occur again on July 22 and 23 (predicted lowest sea level in Victoria Harbour being 0.1 metre) and December 3 and 4 (predicted highest sea level in Victoria Harbour being 2.7 metres) this year.
Members of the public are welcome to visit the following webpage for more information on the real-time and predicted tide for various locations in Hong Kong:
Figure 1. Recorded Tides at Tai Po Kau on 12 January 2005
Figure 2. Recorded Tides at Quarry Bay on 4 July 2004
Figure 3. Tai Po Kau Tide Gauge Station
Figure 4. Hong Kong Observatory Webpage on Tidal Information |
