THE ENVIRONMENT
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men and the international shipping community. This replaced the forecast for fishermen which was broadcast only in Cantonese.
Services for aviation are provided at the Airport Meteorological Office. All aircraft leaving Hong Kong are given briefings, forecasts and weather charts. A continuous watch is kept on the weather at other airports and along air routes.
Every year, more than 20 tropical cyclones form over the western North Pacific and the China Seas causing disruption to shipping and aviation. Tropical cyclones have caused substantial loss of life and property in Hong Kong. Whenever a tropical cyclone is located between latitudes 10°-30° North and longitudes 105°-125° East, warnings for shipping giving forecast positions up to 48 hours ahead are issued every three hours. These warnings are disseminated to ships at sea, to shipping companies and airlines, and to neighbouring countries. Objective forecasts of tropical cyclone movements are made four times daily by computer. The objective forecasts are used as guidance material for forecasters in the Central Forecasting Office and are also sent to other countries in the region. When tropical cyclones approach Hong Kong, warnings are issued at frequent intervals and are widely distributed by visual_signals, telephone, radio and television, along with advice on what precautions to take.
In order to provide these forecasting and warning services, the observatory collects about 15,000 weather reports each day from land stations, ships and aircraft. Coded meteorolo- gical messages are received from Peking, Tokyo and Bangkok through direct point-to-point circuits, and weather reports from voluntary observing ships are received by radio. All the weather reports received are processed by computer to provide analysis charts for use in the Central Forecasting Office.
The observatory operates five meteorological stations in Hong Kong and an extensive network of special observing stations primarily manned by volunteers. These include a network of more than 100 rainfall stations and six tide gauges. The observatory also provides instruments for about 45 selected voluntary ships.
In June, 1979, a temporary meteorological station at Chek Lap Kok Island was estab- lished to collect data for a feasibility study for a new airport. It is equipped with modern instruments including a pulsed laser ceilometer and a spark light visibility meter.
The radar mounted on top of Tate's Cairn, 580 metres above mean sea level, is a valuable aid for tracking the centre of tropical cyclones which move within 400 kilometres of Hong Kong. A video time-lapse system is used in the Central Forecasting Office to record and play back the radar information. In order to receive high resolution photographs from the Japanese geostationary meteorological satellite, a data acquisition system was installed at the observatory towards the end of the year. Pictures received by this system are very helpful to forecasters in the analysis of weather situations and preparation of forecasts.
Apart from routine weather forecasts for the public, specialised weather forecasts are prepared and issued to the power companies and others to suit their individual requirements. The observatory also answers inquiries on climatological and meteorological information from various government departments, industry and the public, and issues certificates for litigation purposes and for insurance claims.
The observatory is responsible for Hong Kong's Time Service. Six-pip time signals are broadcast every 15 minutes on a frequency of 95 megahertz and are relayed by radio and television stations. The signals are also broadcast to ships at sea and aircraft in flight.
Instruments and Measurements
The observatory maintains meteorological instruments at various locations throughout Hong Kong. Anemometers are installed at 12 sites for wind information, which is particu-