ENG-1993 — Page 472

THE ENVIRONMENT

locates cloud-to-ground lightning within a range of about 130 kilometres and a spherics recorder is used to register thunderstorm activity within a range of about 100 kilometres. Assimilation of all information is essential for assessing the likelihood of flooding and landslips.

For the real-time monitoring of floods in northwestern New Territories, water-level and rainfall information at Kam Tin is telemetered directly to the observatory's headquarters. Tide data are collected from eight gauges in the territory for operational warnings of coastal flooding. Numerical models are used to predict the likelihood of storm surges in tropical cyclone situations. Storm surge warnings are issued when a significant rise in the sea-level is forecast.

Besides surface observations, upper air conditions are measured by radiosondes carried by balloons launched at the King's Park Meteorological Station. For an overview of weather systems, hourly high-resolution cloud pictures are received from the Japanese Geostationary Meteorological Satellite. The satellite imageries, which cover East Asia and the western Pacific, greatly facilitate the monitoring of weather systems outside the range of the radar system.

Weather prediction requires constant meteorological data exchange with other countries. This is achieved through telecommunication circuits dedicated to the transmission of meteorological data. The observatory exchanges meteorological data with overseas centres via three international circuits: the Hong Kong-Beijing circuit, the Hong Kong-Tokyo --circuit and the Hong Kong-Bangkok circuit.

In recent years, the vagaries and evolution of weather have become better understood --through experience gained in analysing and interpreting the outputs of numerical weather prediction models run at the Royal Observatory and other major meteorological centres abroad. With the continuing advances in the accuracy and reliability of numerical model outputs, weather forecasts can now be issued several days ahead with confidence.

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Radiation Measurement and Assessment

In line with its responsibilities for emergency response services relating to inclement weather and other natural disasters, the observatory would co-ordinate and formulate technical emergency advice should an unlikely accidental release of radioactivity occur at the Guangdong Nuclear Power Station at Daya Bay, which will begin commercial operations in February 1994. To fulfil this responsibility, the observatory has established an Environmental Radiation Monitoring Programme to monitor radiation levels in Hong Kong. The programme, which began in 1987, entails the collection and measurement of samples of air, water, soil and food regularly at a number of locations in the territory. Measurements from 1987 to 1991 have been analysed to determine the background radiation level in Hong Kong and the results were published in early 1993. A Radiation Monitoring Network has also been established to continuously monitor the ambient gamma dose rate in the territory and to provide an alert in case of any deviation of dose rate from the background level. Since 1993, the collected data has been published monthly. In the event of an emergency, the observatory will monitor and assess the radiological and meteorological information collected to estimate the transport, dispersion and deposition of any radioactivity over the territory, and provide technical advice to the government on any necessary counter-measures.