ENG-1976 — Page 281

THE ENVIRONMENT

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The observatory also monitors radioactivity. Regular measurements of beta and gamma activity in the atmosphere, in rainfall and in tap water have been made since 1961 at the King's Park Meteorological Station. The general level of atmospheric radioactivity during 1976 was low.

The observatory maintains meteorological instruments at various locations throughout Hong Kong. Anemometers are installed at 12 sites as wind information is important during tropical cyclones and is also required in connection with a variety of engineering projects. Other meteorological instruments are operated at Hong Kong International Airport, where the safety of aircraft may at times depend on their reliability and accuracy. As the majority of instruments-both electronic and non- electronic-are unique in Hong Kong, all repairs, calibration and maintenance are done by observatory staff.

The observatory runs a reference library with more than 10,000 volumes of textbooks and periodicals. Besides being necessary to staff members of the depart- ment, the library is used by students, teachers, and research workers from local universities and schools. The library also keeps microfilmed copies of historical weather charts and records, and a comprehensive collection of satellite photographs, radar photographs, and time lapse radar films of various meteorological phenomena.

Research

Investigations and basic research in applied meteorology and geophysics were carried out during the year, and meteorological analyses were undertaken to meet the demand from engineering firms and consultants. Meteorological data and clima- tological information were supplied to other government departments and to local and overseas institutes and organisations. More than 200 technical papers have now been published on various aspects of local weather and on a wide variety of geophysical subjects.

In 1976 the observatory was involved in numerical modelling by computer of the abnormal tide levels that occur during tropical cyclones. The findings will be used to ensure that levels of sea walls, reclamations and drainage of various new towns are adequate to prevent flooding. Data from six tide gauges and three wave recorders in different parts of Hong Kong were used in this investigation. Statistics and related meteorological parameters on storm surges experienced in Hong Kong were compiled, and probabilities of coincidence of storm surges and astronomical tides were determined. A hydrodynamical storm surge model which simulates the propagation of tides generated by tropical cyclones from the South China Sea basin to the inlet of Tolo Harbour is being developed.

A numerical barotropic model is being developed to produce prognostic upper- air weather charts for the improvement of day to day weather forecasts and for the prediction of tropical cyclone movements. During the year, probabilities on the occurrence of fresh, strong, and gale force winds in Hong Kong caused by tropical cyclones over the South China Sea were determined. Meteorological situations that caused extreme temperatures in Hong Kong were investigated and the weather con- ditions associated with or preceding the occurrence of frost in Hong Kong were also studied. A study on evaporation and evapotranspiration was also made.