THE ENVIRONMENT
As a scientific institute, it engaged in method research programmes to cater for the growing demand for more scientific information and to meet the requirements of more sophisticated monitoring programmes. The year's programmes included the analysis of chromium ions (Cr(VI)) in ambient air and water samples; determination of carbonyls in ambient air, lead isotopic ratio analysis for identification source of lead pollution; analysis of dioxins in sediment; and the determination of oxygenates in petrol.
Climate
Hong Kong's climate is sub-tropical, tending towards the temperate for nearly half the year. During November and December, there are pleasant breezes, plenty of sunshine and comfortable temperatures. Many people regard these as the best months of the year.
January and February are cloudier, with occasional cold fronts followed by dry northerly winds. Temperatures can drop below 10 degrees Celsius in urban areas but sub-zero temperatures and frost usually occur on high ground and in the New Territories.
March and April can be very pleasant with occasional spells of high humidity. Fog and drizzle can sometimes disrupt air traffic and ferry services because of reduced visibility.
May to August are hot and humid with occasional showers and thunderstorms, particularly during the mornings. Afternoon temperatures often exceed 31 degrees, but night temperatures generally remain around 26 degrees.
Hong Kong is most likely to be affected by typhoons in September, although tropical cyclones of varying strength are not unusual at any time between May and November. About 31 tropical cyclones form over the western North Pacific and the China Seas every year, and about half of them reach typhoon strength with maximum winds of 118 kilometres per hour or more.
When a tropical cyclone is about 700 to 1 000 kilometres south-east of Hong Kong, the weather is usually fine and exceptionally hot, but isolated thunderstorms sometimes occur in the evenings. If the cyclone's centre comes closer to Hong Kong, winds will increase and rain can become heavy and widespread. The heavy rain may last for a few days, and subsequent landslips and flooding sometimes cause considerably more damage than the winds.
The mean annual rainfall ranges from around 1 300 millimetres at Waglan Island to more than 3 000 millimetres around Tai Mo Shan. About 80 per cent of the rain falls between May and September. August is the wettest month with an average rainfall at the Hong Kong Observatory of 391.4 millimetres and on average rain falls on more than half of the days. The driest month is January with 23.4 millimetres and rain falls only about six days in the month.
Severe weather phenomena that can affect Hong Kong include tropical cyclones, strong winter and summer monsoon winds, monsoon troughs and thunderstorms with associated squalls that are most frequent from April to September. Waterspouts and hailstorms occur infrequently, while snow and tornadoes are rare.
Climatological data are given in Appendix 55.
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