ENG-1986 — Page 346

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THE ENVIRONMENT

Observations of irradiance for the computation of atmospheric turbidity, collection of precipitation samples and measurements of suspended particulate matter were made at the Background Air Pollution Monitoring Network (BAPMON) station at Sai Kung East Country Park for research in long-term climatic change and long-range transport of airborne matter.

Research is also directed at meeting the demand for meteorological analyses by industry and for engineering projects. Other projects during the year included work on design wind and rainfall parameters and modelling of storm surges, sea waves and tides by using computers. Monitoring of the meteorology of the western Victoria Harbour air shed for air pollution potential studies was completed during the year.

In support of the forecast operations, the Royal Observatory develops many of its own microprocessor-based data collection systems.

The Year's Weather

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On the whole, Hong Kong experienced normal weather conditions during the year, 1986. The year's mean temperature recorded at the Royal Observatory was the same as the normal measurement of 22.8°C, while rainfall in the year, totalling 2 338.3 mm, was only five per cent above normal. However, a record low temperature of 4.8°C for the month of March was set on March 1, and hoar frost was reported at Tai Mo Shan and Tate's Cairn on the first two days of the month.

In addition, Typhoon Wayne set a record by being the first tropical cyclone to require the hoisting of warning signals in Hong Kong on three separate occasions, between August 19 and September 5.

A waterspout was reported near Tap Mun and a tornado was reported in Aberdeen on August 21. The Gale or Storm Signal was hoisted twice in 1986, during the approach of Typhoon Peggy in July and Typhoon Wayne in August. Both typhoons caused some damage to Hong Kong.

January was generally fine and sunny with no measurable rainfall. It was the second driest January since records began in 1884. The exceptionally dry weather resulted in 266 hill fires, the most serious of which occurred in Shing Mun Country Park on January 8, and raged for 34 hours, destroying more than 130 000 trees and 900 hectares of plantation land. February was colder and wetter than usual, with a mean temperature of 14.7°C, which was 1.2°C below normal, and total rainfall of 68.8 mm, which was 64 per cent above normal for the month.

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The winter monsoon was active in March,-and a new record low temperature of 4.8°C for the month, was set on March 1. Hoar frost was reported at Tai Mo Shan and Tate's Cairn on the first two days of the month, and temperatures there dropped to -4.0°C and -0.5°C respectively on March 2. The month was also characterised by the frequent occurrence of fog. There was coastal fog on 15 days, a record matched only by that in March 1980.

Under the continued influence of a moist southeasterly airstream, sea fog occurred in the mornings of April 10 and 11, causing disruption to ferry services. Thundery showers on April 21 and 22 caused landslips in Mong Kok, Lai Chi Kok and Pok Fu Lam. Rainfall recorded on these two days at the Royal Observatory amounted to 106.3 mm, accounting for more than 90 per cent of the month's total.

Although the total rainfall for the first four months of the year was below normal, the rainfall in May more than made up for the deficit. The total rainfall recorded at the Royal Observatory from January to May was 615.0 mm, 10 per cent above the normal