ENG-1978 — Page 292

THE ENVIRONMENT

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general release and for individuals. The observatory is responsible for Hong Kong's Time Service and six pip signals are broadcast every 15 minutes on a frequency of 95 megahertz and are relayed by radio and television stations.

As a national weather service, the Royal Observatory operates five meteorological stations in Hong Kong plus an extensive system of special observing stations, manned primarily by voluntary observers. These include a network of more than 100 rainfall stations and seven tide gauges. There also are a number of individual observers from schools, government departments, industry and the general public. The records from these observations are routinely collected and analysed. Various weather summaries, weather charts and reports on tropical cyclones affecting Hong Kong are published. The international responsibilities of the Royal Observatory are primarily centred around aviation and shipping. Aircraft leaving Hong Kong receive briefings, forecasts and copies of weather charts. About 75 flights a day are supplied with meteorological documents. In addition, a continuous watch is kept on the weather at other airports and along air routes.

The Royal Observatory provides instruments for 46 selected ships and an average of about 50 ships send in weather reports each day through Hong Kong's two coastal radio stations. All reports are disseminated to other countries and also punched onto cards for computer use. Special weather bulletins are issued twice daily for inter- national shipping and four times daily for fishermen. Yachtsmen also are provided with weather bulletins during weekends and public holidays.

All weather services provided by the Royal Observatory depend upon efficient communications. Each day, about 10,000 weather reports are received from land stations, ships and aircraft. The coded meteorological information is passed to a computer system for sorting, decoding, printing and archiving. Automatic message switching of meteorological data between Hong Kong, Peking, Bangkok and Tokyo is done by computer.

Both visible and infra-red satellite photographs are received daily from the American polar-orbiting weather satellites and from the Japanese geostationary meteorological satellite.

The tropical cyclone warning service is one of the most important functions of the Royal Observatory. Tropical cyclones are-tracked by radars, satellite pictures and from aircraft and ship reports. Once a tropical cyclone has formed and moved into the area between latitudes 10-30° North and longitudes 105-125° East, the Royal Observatory prepares statements on the present position, intensity and movement of the tropical cyclone as well as issuing forecasts on the expected 24-hour and 48-hour developments. These statements are disseminated to the public, shipping companies and airlines, and to neighbouring countries. Objective forecasts of tropical cyclone movements are made four times daily by computer. These objective forecasts are used by the Royal Observatory and are also sent to other countries.

When tropical cyclones approach Hong Kong, warnings are distributed by visual signals, telephone, radio and television. Information and forecasts are broadcast at frequent intervals with regular advisory bulletins and precautionary announcements. The Royal Observatory displays signals for various stages of alert when tropical cyclones come within 750 kilometres of Hong Kong. The signals are based upon the forecast or actual effect of the tropical cyclone on Hong Kong. If the centre of a