ENG-1973 — Page 251

THE ENVIRONMENT

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Louise were the only two tropical cyclones reported in the western north Pacific and the South China Sea. Both formed in the vicinity of north Luzon and moved west- wards across the South China Sea causing freshening of winds over Hong Kong. Two surges of the winter monsoon passed through Hong Kong and necessitated the hoisting of the strong monsoon signal on September 24 and 27-28.

October was much drier than normal. Only 4.7 mm of rainfall were recorded during the month, representing less than five per cent of the average amount for October. On October 28, the relative humidity fell to a minimum of 21 per cent which was the lowest on record for October and was equalled once previously, in October 1968.

Four typhoons were reported in the month but only Typhoons Nora and Ruth came sufficiently close to affect Hong Kong. The strong-monsoon signal was hoisted on three occasions during outbreaks of cold air from the north.

No measurable rainfall was recorded during the first 24 days of November and the month's total rainfall amounted to only 9.3 mm against the average value of 43.1 mm. During the month, two tropical cyclones were reported over the South China Sea and one near the Philippines, but none affected Hong Kong. Due to dry weather conditions, fire danger warnings were in operation on 25 days of the month.

An intense and persistent continental anticyclone dominated China and the neighbouring seas during December and resulted in exceptionally dry and clear weather in Hong Kong. The month was the sunniest December since 1939 and the mean relative humidity and dew point were both the lowest on record for December. On December 31, the relative humidity fell to a minimum of 14 per cent which was the lowest ever experienced for the month. No measurable rainfall was recorded during December and a fire danger warning was in force every day. The strong monsoon signal was hoisted three times during the intensification of the northeast

monsoon.

The year will be remembered for the exceptionally wet and cloudy summer and the unusually persistent clear and fine weather in November and December.

The Royal Observatory

The Royal Observatory is directly concerned with all matters relating to meteorology, geophysics and environmental sciences. It provides a diversity of services on a broad spectrum of environmental problems. These services not only play an important role in the economic progress and development in a modern society like Hong Kong, but also help reduce possible loss of life and property in natural catastrophes caused by severe weather systems such as thunderstorms, rain- storms and tropical cyclones.

Weather forecasts and tropical cyclone warnings are prepared in the Central Forecasting Office, while services for aviation are provided at the Airport Meteoro- logical Office.