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GEOGRAPHY AND CLIMATE

humidity at all levels through which the balloons ascend. The Obser- vatory also maintains a network of about 150 rain gauges through- out the Colony.

At the Airport Meteorological Office, pilots of all aircraft leaving Hong Kong are briefed and provided with written forecasts and weather charts to internationally agreed specifications. Information is also exchanged with other centres and radioed to aircraft in flight.

Close liaison is maintained with all ships that visit Hong Kong and about sixty selected ships are provided with instruments by the Observatory to assist them to transmit regular and accurate weather reports which are of great value in the locating of tropical cyclones and the preparation of forecasts for shipping. About 75 weather reports are received each day from ships, through two radio stations. They are re-broadcast to other centres. In addition about 5,000 weather reports from land stations and ships are received each day from other countries. They are all plotted and analysed at the Royal Observatory. Special weather bulletins are broadcast for shipping and for fishermen.

One of the most important functions of the Royal Observatory is to issue warnings of Tropical Cyclones. Whenever a Tropical Depression, Tropical Storm or Typhoon 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 for 24 hours ahead. Reliable reports from ships and reconnaissance aircraft and cloud pictures received at the Royal Observatory direct from meteorological satellites help to locate the storm accurately.

When the Colony itself is threatened, the local storm warning system is brought into use and warnings are widely distributed by means of visual signals, telephone, radio and television. Statements and announcements about necessary precautions are also broadcast at frequent intervals whenever local signals are displayed.

The Observatory's weather radar station at Tate's Cairn is equipped with a three cm radar for detecting showers and local rainstorms and a ten cm radar, for locating tropical disturbances up to 240 miles away. The latter radar can also be used to estimate