ENG-1980 — Page 304

THE ENVIRONMENT

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services and tropical cyclone warnings for the public and for international shipping and aviation.

Routine weather forecasts are prepared and broadcast over radio and television at frequent intervals every day. Warnings of fire danger or hazardous weather

such as thunderstorms, heavy rain, and low temperatures - are issued whenever necessary. Special marine forecasts are issued for ships in the China Seas and for fishermen and yachtsmen in coastal areas.

Services for aviation are provided by the Airport Meteorological Office. All aircraft leaving Hong Kong are given briefings, forecasts and weather charts for various flight levels. A continuous watch is kept on the weather at other airports and along air routes. Every year, more than 20 tropical cyclones affect the western North Pacific and China. Seas; some of them develop winds of hurricane force (64 knots or more), and are then called typhoons. Warnings and forecasts are issued every three hours for ships at sea, for shipping companies and for airlines. Objective forecasts of tropical cyclone movements are made by computer. Whenever tropical cyclones approach Hong Kong, warnings and statements are issued at frequent intervals and are widely distributed by visual signals, telephone, radio and television.

In order to provide these services the observatory collects about 15,000 weather reports each day from land stations, ships and aircraft. Coded messages are analysed by the observatory's computer and exchanged automatically with neighbouring countries. The observatory has accumulated a wide variety of historical weather records, mostly on computer tape and microfilm. These are used to provide data for a variety of organisations involved in planning, research, insurance, industry, and teaching, both in Hong Kong and overseas.

The most significant event of 1980 was the opening of the observatory's new satellite ground station on January 24. Satellites have revolutionised tropical meteorology and the observatory's new ground station is proving just how much, as it receives pictures from the Japanese geostationary meteorological satellite (GMS), every three hours. The pictures are enlarged and enhanced by a special computer to the extent that even bush fires in Australia can be identified. It is now possible from these satellite pictures to locate the centre, and estimate the maximum winds in a tropical cyclone, almost as accurately as from a reconnaissance aircraft.

Another important advance in 1980 was the modernisation of the observatory's time service. Until 1966, the observatory provided time signals derived from pendulum clocks. A thermostatically controlled crystal clock was installed in 1966, but in 1980 the observatory acquired its first caesium beam atomic clock. Time signals from the new clock are accurate within a few microseconds and should not only improve navigation but also provide a valuable calibration standard for Hong Kong's expanding watch and clock industry. Six pip time signals are broadcast from the observatory headquarters every 15 minutes and relayed by radio and TV stations.

Instruments and Observations

The observatory operates six meteorological stations in Hong Kong and a network of special observing stations manned mainly by volunteers. These include more than 100 rainfall stations and two tide gauges. The observatory also provides instruments for about 40 selected ships. A radar station on the top of Tate's Cairn (580 metres), is connected to displays in the observatory and at the Hong Kong International Airport and is used for tracking tropical cyclones and thunderstorms to a radius of about 400 kilometres.