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GEOGRAPHY AND CLIMATE
the problem of air pollution by sulphur dioxide was also investigat- ed. Research on methods of forecasting the movement of typhoons made good progress during the year.
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THE YEAR'S WEATHER
Although several weather records were broken during 1966, the year will probably be remembered chiefly for the severe rainstorm in June, which caused the most disastrous floods and landslides ever experienced in Hong Kong. Rainfall was well above normal, but the autumn was the driest on record. Total rainfall from 1st September to 31st December was only 49.4 mm (1.94 inches) compared with a normal 446 mm (17.56 inches). The year began with very warm weather; above normal temperatures were recorded on 99 out of the first 120 days. The strong monsoon signal was hoisted for several hours in February and there were strong winds at Waglan Island and in exposed places. The winter monsoon was frequently interrupted in March, and Hong Kong saw extensive sea fog in the harbour areas in the mornings of the 2nd and 6th, and again on the 14th, 15th and 17th. Four surges of cold air affected the Colony during the month but only two produced an appreciable fall in temperature. The strong monsoon signal was hoisted on 18th and 19th March, and strong winds prevailed in exposed places and over the Colony waters.
April was unusually wet, with more than twice the normal rainfall for the month. On 4th April a heavy thunderstorm brought 190.2 mm (7.49 inches) of rain to the Colony between 6 p.m. and midnight. This figure represents the highest rainfall ever recorded in any April day in Hong Kong. May was dry and sunny and the mean dew point and mean relative humidity were the lowest ever recorded for the month. Although the passage of a trough of low pressure on 16th May brought 91.1 mm (3.59 inches) of rain, the total rainfall for the month was less than half the normal amount. Severe tropical storm Judy developed over the southern part of the China Sea on 25th May. It moved northwards at first but recurved towards north-east after reaching a position about 150 miles south-east of Hong Kong, and did not cause strong winds over the Colony.
In June an active trough of low pressure persisted for an ex- ceptionally long period along the south China coast and as a result,