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THE ENVIRONMENT
flooding and traffic disruption. The Observatory also issues warnings on thunderstorms, landslips, fire danger, strong monsoon, cold and very hot weather, and frost. An advisory service on the ultraviolet (UV) index is also provided.
With the advancement of telecommunication technology in recent years, the century-old system of providing storm warnings by hoisting visual signals became obsolete. Over 40 signal stations were closed since the late 1970s and the last signal station, on Cheung Chau, was decommissioned on January 1.
Weather programmes for the public are presented regularly on television by the Observatory's meteorologists. During adverse weather, interviews and briefings are given over the radio and television. Weather information is disseminated to commercial communications services, making it available on various electronic media. The Dial-a-Weather service operated by the Observatory provides recorded weather messages to the public. In 2002, some 20 million calls were handled. The Telephone Information Enquiry System is an interactive system through which the public can obtain a variety of meteorological, geophysical and time information by phone or by fax. In 2002, the system handled over 820 000 enquiries.
The Observatory maintains an informative home page. To facilitate accessibility, it features an audio version for the visually impaired and a WAP (Wireless Application Protocol) version for mobile phone users. In 2002, a simplified Chinese version was added. The total number of pages visited in 2002 exceeded 182 million, or about 500 000 per day on average. Furthermore, the Observatory has set up two websites on behalf of the World Meteorological Organisation to make official weather warnings and forecasts around the world available to the international community.
Weather Monitoring and Forecasting
The Observatory exchanges weather observations and forecasts with the rest of the world. Imagery from a number of geostationary and polar-orbiting meteorological satellites operated by weather services in China, Japan and the United States are received regularly to monitor important weather systems such as tropical cyclones, rainstorms and cold fronts.
The Observatory's Doppler weather radar at Tai Mo Shan provides high-resolution rainfall and wind data in respect of weather systems within 500 kilometres of Hong Kong. Weather observers and 67 automatic weather stations provide comprehensive coverage of regional weather variations in Hong Kong, while observations from Voluntary Observing Ships provide valuable information of weather at sea. In 2002, two weather buoys were installed over waters west of the Hong Kong International Airport at Clek Lap Kok in an experiment to monitor windshear due to sea breeze and fronts.
Floods and landslips during heavy rain are potentially hazardous. A network of 111 automatic raingauges provides real-time information on rain distribution and intensity for the operation of rainstorm and landslip warnings. An operational nowcasting system combines radar and raingauge analysis to forecast rainfall up to three hours ahead.
The Observatory runs high-resolution numerical weather prediction models using a high-speed computer. Using guidance from numerical products from the Observatory's own model and those of other meteorological centres, forecasters can now issue weather forecasts several days ahead with reasonable confidence.