THE ENVIRONMENT
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oil refinery operations in Hong Kong, the siting of incinerators, desalters and power stations and the planning of land use.
During the year, an investigation on the mean thermal structure of tropical cyclones was completed, using more than 100 upper-air soundings made within their circulations. The rainfall associated with tropical cyclones which affected Hong Kong was also examined and the characteristics of rain cells as revealed by radar studied. Tropical cyclone tracks in the western North Pacific and the China Seas for the period 1884-1970 were revised and up-dated and part of the results are being published as Royal Observatory Hong Kong Technical Memoir No. 11, Volume 1. This publica- tion contains basic charts of tropical cyclone tracks for standard five-day periods and relevant eye-fix data derived from reconnaissance aircraft reports.
Detailed statistical analyses of the 'probabilities of dry and wet days in Hong Kong were carried out and new techniques for improving the siphoning efficiency of autographic raingauges used in Hong Kong's rainfall observing network were developed.
An investigation on the sea-wave characteristics off Waglan Island was also initiated for the purpose of estimating the probable maximum height of sea-waves in that area under typhoon conditions.
Pollution Monitoring and Control
The Royal Observatory is responsible for providing basic information to enable warnings to be issued of any possible health hazards due to radioactive fallout from old and fresh nuclear explosions. This, and regular measurements of beta and gamma activity in the atmosphere and in rainfall have been made since 1961 at the King's Park Meteorological Station of the Royal Observatory. The radioactivity of filtered water samples from several reservoirs in the territory is also regularly monitored. The issue of licences for irradiating apparatus and radioactive substances is controlled by a Radiation Board set up within the Medical and Health Department. The board's effectiveness is assured by two sets of regulations which, taken together, cover the entire field of control in relation to radiation. The two radiation regulations are the Control of Radioactivity Substances, and the Control of Irradiating Apparatus.
The Advisory Committee on Air Pollution was reconstituted in December 1970 as a permanent advisory committee under the chairmanship of Mr J. L. Marden, JP. Its members are drawn from various government departments including the Royal Observatory, Public Works, Medical and Health, Urban Services, Labour and Trans- port, as well as from the Colonial Secretariat. A number of unofficial members are appointed for their special interest or expertise in this field. The committee's terms. of reference are to keep the state of air pollution in Hong Kong under constant review and to advise the government on appropriate measures for its control.
Regulations are being drafted under the Clean Air Ordinance requiring owners of premises to submit plans of all new or proposed modifications of existing furnaces and chimneys, as well as setting standards to ensure that the combustion of liquid fuels will produce a minimum of dark smoke. Consideration is also being given to