ENG-1972 — Page 250

THE ENVIRONMENT

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important role in the economic progress and development in a modern society like Hong Kong, but also help to reduce the possible loss of life and property in natural catastrophes caused by severe weather systems such as thunderstorms, rainstorms 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 Meteor- ological Office.

Close liaison is maintained with all ships visiting Hong Kong and about 45 selected ships are provided with instruments by the Observatory to encourage them to transmit weather reports which are used in the preparation of forecasts and for locating tropical cyclones. About 60 weather reports are received each day from ships, through two coastal radio stations in Hong Kong. All reports received are dissemi- nated to other centres through the World Weather Watch telecommunication network. In addition, about 5,000 weather reports from land stations and ships are received each day from other countries together with aircraft reports and other data. They are decoded, plotted and analysed at the Royal Observatory. Special weather bulletins are broadcast for shipping and for fishermen, and all aircraft leaving Hong Kong are given briefings, written forecasts and weather charts.

One of the most important functions of the Royal Observatory is to issue warn- ings of tropical cyclones. Whenever a tropical cyclone is located within the region bounded by latitudes 10°-30° north and longitudes 105°-125° east, six-hourly and often three-hourly non-local warnings are issued. These provide information on the maximum winds, the position and movement of the centre and the forecast position 24 hours ahead. Reports from ships and reconnaissance aircraft and cloud pictures received at the Royal Observatory direct from meteorological satellites are used to locate the centre and evaluate the intensity of the tropical cyclone.

When Hong Kong itself is threatened, warnings are widely distributed by means of visual signals, telephone, radio and television. Advice and recommended precau- tions are broadcast at frequent intervals whenever signals are displayed. The Royal Observatory also issues thunderstorm and heavy rain, fire hazard, frost and low temperature warnings whenever necessary.

The Observatory's weather radar station at Tate's Cairn is equipped with a three-centimetre radar for detecting showers and local rainstorms and a 10-centimetre radar for locating larger tropical disturbances up to 240 nautical miles away. A new iso-echo device was fitted to the latter radar to facilitate the real-time estimation of the intensity of rainfall. This equipment now provides valuable additional information for rainfall forecasting as well as for hydrological applications.

The Observatory is responsible for Hong Kong's Time Service. Six pip signals from a special crystal clock, accurate to 0.05 second, are broadcast every 15 minutes on a frequency of 95 MHz and are relayed by the various broadcasting and television stations. With effect from January 1, 1972, the time kept by the Hong Kong Time Standard was changed to Universal Co-ordinated Time (UTC). This new time system has been adopted by international agreement and is based on an atomic time standard