ENG-1982 — Page 318

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THE ENVIRONMENT

The Royal Observatory

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The Royal Observatory was established in 1883 mainly to provide scientific information for the safe navigation of ships. The headquarters of the department has remained in the same building for 99 years, with the construction of a new nine-storey office block beside the original headquarters completed in 1982.

The most important function of the department is the provision of weather information and tropical cyclone warnings for the public, shipping and aviation. Forecasts for the public are prepared in the Central Forecasting Office and broadcast over radio and television at frequent intervals. Warnings of thunderstorms, heavy rain, fire danger, strong monsoon and frost are issued whenever necessary. Forecasts are also issued for shipping at sea, fishermen in coastal waters and yachtsmen.

Services for aviation are provided by the Airport Meteorological Office. About 80 aircraft each day are supplied with meteorological prognostic charts and landing forecasts. Special warnings are issued for adverse weather. A micro-processor-based system provides a continuous display of wind shear occurring in the approaches to the airport.

On average, 31 tropical cyclones form in the western North Pacific or China Seas every year and about half of them reach typhoon intensity (maximum winds of 33 metres per second or more). Warnings are issued every three hours for ships at sea, shipping companies and airlines. Objective forecasts of tropical cyclone movements are made by computer and exchanged with neighbouring meteorological centres. Whenever tropical cyclones threaten Hong Kong itself, warnings and advice on precautions are issued at frequent intervals and widely disseminated. In order to provide these services the Central Forecasting Office receives about 20 000 weather reports each day from land stations, islands, ships and aircraft. Code messages are analysed by computer and exchanged automatically with neighbouring countries. A comprehensive data bank of historical weather records has been accumulated on magnetic tapes and is used to answer climatological enquiries from organisations such as engineering consultants, universities, utilities, and insurance and legal firms, both in Hong Kong and overseas.

During the year, a system for warning squatters of the danger of landslips caused by prolonged heavy rainfall was reviewed and improved.

Instruments and Observations

High resolution satellite pictures from the Japanese Geostationary Meteorological Satellite (GMS) continued to be received in Hong Kong. The pictures are recorded on magnetic tape in digital form and any area can be enlarged and enhanced by micro-processors. Special enhancements are used to estimate the maximum winds in a tropical cyclone.

Work was in progress to replace the weather radar at Tate's Cairn. The improved radar will provide estimates of rainfall rates over a wide area and also archive the data for research purposes. The old radar is being maintained as a back up.

The observatory operates an upper-air sounding system. Instead of being tracked by radar, as in conventional systems, the radiosondes relay Omega navigation signals to the ground station at King's Park and a mini-computer calculates the upper winds from changes in the phase of these signals. A new tethered radiosonde system was introduced in 1982 to obtain meteorological data at various heights above the ground.

Regular meteorological observations are made at the Royal Observatory, Kai Tak, Cheung Chau and Chek Lap Kok. Additional reports are provided by the Marine Department at Waglan Island and Green Island and by the Royal Navy at Tai O. The observatory operates more than 100 raingauges sited throughout the territory. There are