THE ENVIRONMENT
several sites in Hong Kong. Measurements from 1987 to 1991 were analysed to determine Hong Kong's background radiation levels and the results published in early 1993. Thereafter, bulletins on the prevailing radiation levels have been published annually. A network has also been established for continuous monitoring of the ambient gamma dose rate in Hong Kong and to warn of any deviation from normal levels. Data are disseminated to the media daily and published in a bulletin every month.
In any emergency, the Observatory will intensify radiation monitoring and assess the radiological and meteorological information collected to estimate the transport, dispersion and deposition of any radioactivity over Hong Kong. It will also give the government technical advice on any necessary counter-measures.
Climatological, Oceanographic and Geophysical Services
Climatological information finds applications in activities ranging from recreation through engineering design and environmental impact analysis to litigation. To meet the demand for such information, the Hong Kong Observatory operates a climatological information service on a cost-recovery basis. The data available include land and upper-air observations from Hong Kong and neighbouring countries, marine weather observations from voluntary observing ships, and tidal observations.
The Observatory produces an annual tide table for Hong Kong. It also provides assessments of the probabilities of occurrence of extreme storm surges and waves and its advice on oceanographic matters is often sought by other government departments and the engineering community.
To monitor earthquake activities in the vicinity of Hong Kong, the Observatory operates a network of eight short-period seismograph stations. Long-period seismographs at the Observatory's headquarters detect tremors world-wide and information on significant tremors is made public through the media. In addition, three strong motion accelerographs were installed on different geological sites. On average, Hong Kong experiences two to three minor earth tremors every year. Seismic data are used by structural engineers in building design, and by local and overseas scientific institutions.
The Hong Kong Time Standard is provided by a caesium beam atomic clock. Accuracy within fractions of a microsecond a day is maintained. A six-pip time signal is sent to Radio Television Hong Kong for broadcast at quarter-hour intervals.
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