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GEOGRAPHY AND CLIMATE
Much effort was given to the study of rainfall patterns and anomalous propagation of electromagnetic waves by means of the radar. New objective techniques were developed for predicting the movement of tropical cyclones over the western Pacific and the South China Sea, and an investigation was started to examine the structure of synoptic systems which affect Hong Kong, by analysing cloud pictures received from meteorological satellites. The pre- liminary findings from these studies have proved to be useful for operational forecasting purposes.
Various problems on air pollution were investigated, including the effect on smoke on visibility in the Hong Kong Harbour and the effect of wind and temperature inversions on the concentration of sulphur dioxide in the atmosphere. An analysis of the vertical distribution of temperature and humidity over the Colony was made in relation to tropospheric scattering and ducting in tele- communication problems.
The Royal Observatory also co-operated with several other oversea scientific institutes in many special research projects in seismology, radio-activity, marine climatology and atmospheric chemistry.
THE YEAR'S WEATHER
The year 1968 was slightly sunnier and warmer than usual. The total rainfall for the year, 2,288.2 mm (90.09 inches) was close to the normal value 2,168.8 mm (85.39 inches).
January was warm and sunny with very little rain. In contrast, February was dull and very cold with a mean temperature of only 11.7°C, the lowest ever experienced in the Colony since records began in 1884. Sleet fell near the top of Tai Mo Shan on February 13 and ice was also observed on February 15 when the air temperature dropped to minus 2.5°C.
Fog occurred on many days during March and early April causing a total of 55 in-bound aircraft to be diverted. Between March 23 and 29, a slow-moving trough brought widespread thunderstorms to the Colony and 140.4 mm (5.53 inches) of rain were recorded.