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microprocessor system and displayed at the Central Forecasting Office. Implementation of the plan to acquire water level data at Kam Tin River and Yuen Long Flood Channel in real-time continued. A local network of automatic weather stations at Ta Kwu Ling, Lau Fau Shan, Chek Lap Kok, Tsing Yi and Sha Tin sends weather data to the observatory headquarters via telephone lines.
Another automatic weather station is operated at Huangmao Zhou, an island 40 kilometres to the south of Lantau Island, in collaboration with the Guangdong Meteoro- logical Bureau. Several tide gauges are also operated by the Royal Observatory, and these send information instantaneously to the observatory headquarters from stations at Lok On Pai, Quarry Bay, Tai Po Kau and Tsim Bei Tsui. Wave data are collected at Waglan Island.
Tide tables for Hong Kong for 1987 were produced for the first time on the basis of predictions made by the Royal Observatory.
Upper-air atmospheric conditions are measured by radiosondes carried by balloons launched at King's Park Meteorological Station. Signals transmitted by the radiosondes are processed by a minicomputer on the ground.
A digital radar system which employs a minicomputer to process radar signals supplies information on rain distribution to forecasters at the Central Forecasting Office and the Airport Meteorological Office. The system also produces objective short-term rainfall estimates at selected locations.
High resolution satellite cloud pictures from the Japanese Geostationary Meteorological Satellite are received in Hong Kong. The pictures, recorded in digital form, are processed by microprocessors to give special displays for estimating rainfall intensity and maximum winds in a tropical cyclone. When necessary, satellite pictures transmitted by polar-orbiting meteorological satellites are also received, supplementing information from the geostation- ary satellite.
During the year, orders were placed to acquire additional data processing equipment to cater for various new applications in the department, including automation of weather chart plotting and local dissemination of weather information, improved quality control and processing of meteorological data, numerical modelling for forecasting and warning services.
The observatory has been measuring Beta and Gamma radioactivity in airborne dust and rain-water since the early 1960's. In 1986 a comprehensive programme of monitoring the background radiation in Hong Kong was launched. The programme is designed to establish an accurate baseline of the background radiation levels in Hong Kong prior to the commissioning of the nuclear power plant at Daya Bay in 1992.
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 and is also relayed to Radio Television Hong Kong for broadcast to the public.
Research
The Royal Observatory carries out investigations on weather systems affecting Hong Kong with a view to improving the standard of weather services. The performance of existing objective methods of forecasting tropical cyclone movement was assessed and new methods were introduced. Several recent tropical cyclones were analysed in detail.
Development of numerical weather prediction methods for timely forecasts and warnings of hazardous weather systems continued. Computer models were being adopted and tested for application in flood forecasting.
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