GEOGRAPHY AND CLIMATE
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new 10 cm radar, installed there in 1966, is capable of detecting tropical disturbances up to 240 miles away from Hong Kong. This radar can also be used to estimate the intensity of rainfall from various weather systems and provides valuable information for preparing local thunderstorm and heavy rain warnings as well as for local hydrological purposes.
Time signals are provided by the observatory by means of the new crystal-controlled timing system installed in 1966, which is accurate to within 0.05 of a second. These signals are broadcast every quarter of an hour on a frequency of 95 MHz (frequency modulated), and can be picked up by a domestic FM receiver. In addition, visual time signals are flashed from the observatory during the hours of darkness.
The observatory operates 12 seismometers, distributes weekly and monthly reports of earthquakes and also participates in the Pacific tidal wave warning service. Hong Kong lies some distance away from the circum-Pacific seismic belt and serious earthquakes are unknown. However, a few tremors are felt each year by people in favourable locations. Four such tremors occurred in 1967.
The general level of atmospheric radio-activity in the Colony is monitored by the observatory at King's Park, where routine measure- ments of the Beta and Gamma activities of fallout, airborne particles near the ground, rainfall and ordinary tap water are carried out. The observatory acts in an advisory capacity in the planning of a great many projects that may be affected by meteorological condi- tions and publishes numerous, reports, bulletins and papers on meteorological and geophysical observations and research activities.
RESEARCH
Many climatological and statistical investigations and analyses were carried out during the year for aviation, shipping and local engineering interests or for use within the department. Various methods of forecasting rainfall quantitatively were studied and some of them were developed with the aid of a computer at the University of Hong Kong. Studies on the prediction of the probable rainfall for the rainy season, and for individual months within the season, were also carried out. Experiments were initiated to determine the distribution of rain-drop sizes in clouds over Hong Kong and the
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