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THE ENVIRONMENT
set standards for bathing beach waters which the public can rely on to protect health. Meanwhile, information on the microbial quality of all bathing beaches in Hong Kong is released on a biweekly basis during the bathing session, in the form of beach gradings.
A comprehensive environmental monitoring programme, initiated in 1987, continued during 1988 at the proposed marine disposal area east of Waglan Island for sludges arising from the sewage and water treatment works in the Sha Tin area. The programme involved the sampling and analysis of water, sediment and biological samples and the data collected will be used as the base against which to judge the environmental effects of the marine disposal of sludges.
Waste arisings are monitored annually and the information is used to plan future waste disposal facilities. In 1988 waste quantities increased by 22 per cent from an average of 10 800 tonnes a day in 1987 to 13 200 tonnes a day. This increase was due almost entirely to an increase in construction waste arisings, which were 56 per cent greater than in 1987 and which made up 50 per cent of total arisings. This reflects the massive increase in construction activity in general, and redevelopment of the older urban areas in particular, that has taken place in 1987 and 1988.
The landfills at which most solid wastes are deposited are also monitored. The tests carried out are designed to assess leachate quantity and quality, the degree of surface and groundwater contamination, and the presence or otherwise of potentially harmful gas emissions.
Climate
Hong Kong's climate is sub-tropical, tending towards 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 have rather more cloud, with occasional cold fronts followed by dry northerly winds. It is not uncommon for temperatures to drop below 10°C in urban areas. The lowest temperature recorded at the Royal Observatory is 0°C, although sub-zero temperatures and ice occur at times on high ground and in the New Territories.
March and April can also be very pleasant except for occasional spells of high humidity. Fog and drizzle can be particularly troublesome on high ground exposed to the southeast, and air traffic and ferry services are occasionally disrupted by reduced visibility.
May to August are hot and humid with frequent showers and thunderstorms, par- ticularly during the mornings. Afternoon temperatures often exceed 32°C; at night, temperatures generally remain around 26°C with high humidity. There is usually a fine dry spell in July which may last for one to two weeks, or even longer in some years.
September is the month during which Hong Kong is most likely to be affected by tropical cyclones, although gales are not unusual at any time between May and November. On average, about 30 tropical cyclones form in the western North Pacific or China Seas every year, and about half of them reach typhoon strength (maximum winds of 118 kilometres per hour or more).
When a tropical cyclone is about 700 to 1 000 kilometres southeast of Hong Kong, the weather is usually fine and exceptionally hot, but isolated thunderstorms sometimes occur in the evenings. If the centre moves closer to Hong Kong, winds increase and rain can become heavy and widespread. Heavy rain from tropical cyclones may last for a few days and subsequent landslips and flooding sometimes cause more damage than the winds.
The mean annual rainfall ranges from around 1 200 millimetres at Waglan Island to more than 3 000 millimetres in the vicinity of Tai Mo Shan. About 80 per cent of the rain