THE ENVIRONMENT
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In order to provide these services, meteorological data are received from other countries through a computerised telecommunications system. This information is regularly analysed and supplied to forecasters while the coded messages are exchanged automatically with neighbouring countries.
Weather observers at the Royal Observatory headquarters, Hong Kong International Airport and Cheung Chau keep a continuous watch on local conditions. Additional observations are made by the Marine Department at Waglan Island and Green Island, and by the Royal Navy at Tai O. Fifteen anemometers are operated by the observatory in different locations. Winds recorded at the Star Ferry Pier, Kowloon and at Waglan Island, representing conditions in Victoria Harbour and offshore respectively, are telemetered to the Central Forecasting Office. A spherics recorder is used to register thunderstorm activity within a range of about 100 kilometres. Automatic rain-gauges report rainfall amounts instantaneously through a micro-processor system, complementing the network of more than 100 conventional rain-gauges, mostly read by volunteer observers. Tide readings at Tai Po Kau, North Point, Lok On Pai and Chek Lap Kok are telemetered to the Central Forecasting Office providing important information in the warning of floods during the approach of tropical cyclones. A wave recorder at Waglan Island gives a continuous record of waves.
The observatory's historical weather records are used to answer climatological enquiries from local and overseas organisations such as engineering consultants, universities, utility companies, and insurance and legal firms. It is designated by the World Meteorological Organisation as the centre for marine meteorological data for the South China Sea and advice on marine climatological conditions is given when requested.
Upper-air atmospheric conditions are measured by radiosondes carried by balloons released at King's Park Meteorological Station. The radiosondes relay Omega navigation signals to the ground station and a mini-computer calculates the upper winds from changes in the phase of these signals. A tethered radiosonde system is used at selected locations to obtain data up to a few hundred metres above the ground.
A new weather radar was installed at Tate's Cairn during the year. The radar employs a mini-computer to produce displays for the reference of forecasters and short-term estimates of rainfall over a wide area. The old radar is being maintained as a back-up.
High resolution satellite cloud pictures from the Japanese Geo-stationary Meteorological Satellite continued to be received in Hong Kong. The pictures, recorded in digital form, are processed by micro-processors to give special displays for purposes such as to estimate maximum winds in a tropical cyclone.
In order to monitor local earthquakes, a network of three short-period seismometers at Cheung Chau Island, High Island and Tsim Bei Tsui is operated by the Royal Observatory. Long-period seismographs record tremors from all over the world. Strong motion accelerographs are installed at three locations with different soil properties. While on average only two or three earthquakes are felt by the public each year, hundreds are detected by the seismometer network; in 1983 about 100 earthquakes were detected within 320 kilometres of Hong Kong.
Measurements of Beta and Gamma radio-activity in airborne dust and rain-water are made at King's Park. The observatory co-operates with the UK Atomic Energy Research Establishment and the International Atomic Energy Agency in these measurements.
The observatory operates a caesium beam atomic clock which provides time signals accurate to about one micro-second. A six-pip signal is broadcast on 95 MHz every quarter hour.