THE ENVIRONMENT
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Whenever Hong Kong is threatened by tropical cyclones, frequent warnings with advice on the necessary precautions to take are widely disseminated. A colour-coded rainstorm warning system is activated to warn people of serious road flooding and traffic disruption. The Observatory also warns of thunderstorms, floodings, landslips, fire danger, strong monsoon and frost.
Weather programmes for the public are presented regularly on television by the Observatory's meteorologists. During adverse weather, live interviews and briefings are given by weather forecasters over the radio and television.
For people requiring instant access to weather forecasts, warnings or tropical cyclone information, the Observatory operates a Dial-a-Weather automatic tele- phone answering system. About 60 000 calls were received on an average day in 1995, totalling more than 20 million calls for the year. Weather information is also provided to commercial communications and paging services which make it avail- able on various electronic media. The Royal Observatory produces a variety of meteorological and climatological publications, most of which are free-of-charge and obtainable from the Royal Observatory.
Weather Monitoring and Forecasting
To provide weather forecasts and warnings of hazardous weather, the Royal Observatory maintains a close meteorological watch round-the-clock.
The Observatory exchanges weather observations with the rest of the world through the Global Telecommunications System operated under the auspices of the World Meteorological Organisation. The data exchanged include observations made by land stations, ships and buoys. Through its telecommunication lines with meteorological centres in Beijing, Tokyo and Bangkok, the Royal Observatory receives about 20 000 weather reports each day.
Cloud pictures covering East Asia and the western Pacific are received from Japan's Geostationary Meteorological Satellite every hour. They show cloud systems and give general indications of frontal systems, severe storms and tropical cyclones approaching the South China coast. The Observatory's Doppler weather radar system at Tate's Cairn detects rain areas within about 500 km of Hong Kong, and measures the rain intensity and movement. Thunderstorms are detected and located by a lightning location system.
Weather observers and automatic weather stations at about 30 locations in Hong Kong provide a comprehensive and real-time coverage of regional weather variations, while observations from Voluntary Observing Ships provide valuable information on weather at sea.
Rainfall information is important because of the territory's vulnerability to floods and susceptibility to landslips during heavy rain. A dense network of more than 60 automatic reporting rain-gauges provides real-time information on rain distribution and intensity over Hong Kong for the operation of rainstorm, flood and landslip warnings.
The Observatory operates tide gauges for monitoring coastal flooding and raised sea levels caused by tropical cyclones. To probe the atmosphere aloft, radiosondes carried by balloons are launched four times a day at King's Park to relay weather information from the upper air.