Hong Kong Observatory

The Hong Kong Observatory was established in 1883, mainly to provide scientific information for the safe navigation of ships. Since then, it has evolved in line with community needs providing services in and studies on weather forecasting, hydrometeorology, climatology, physical oceanography, aviation and marine meteorology, and radiation monitoring and assessment. The Observatory also operates the official time standard for Hong Kong, provides basic astronomical information and maintains a seismological monitoring network.

    The Central Forecasting Office at the Observatory's headquarters is responsible for issuing weather forecasts and warnings of hazardous weather. Its marine weather forecasts cover the South China Sea. Forecasts and advice are also provided to civil aviation, business and industrial communities, port and container terminal operators.

    Whenever Hong Kong is threatened by tropical cyclones, frequent warnings are widely disseminated together with advice on the precautions to take. A colour-coded rainstorm warning system warns people of heavy rain that may cause serious road 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.

    In March, the Observatory issued an experimental forecast on the total rainfall and the number of tropical cyclone affecting Hong Kong in the year, as part of a pilot study on short range climate forecasting.

    The Observatory operates tide gauges to monitor raised sea levels and coastal flooding caused by tropical cyclones. Radiosondes carried by balloons are launched three times a day at King's Park to measure weather conditions aloft. Three wind profilers are installed at different locations to probe the upper-level winds every 10 minutes. One of them includes a radio acoustic sounding system to sense temperatures in the lower atmosphere.

    The Observatory exchanges weather radar images with the Guangdong Meteorological Bureau and operates jointly with it four solar-powered automatic weather stations at islands in the Pearl River Estuary area to provide better timing of the approach of hazardous weather such as fronts, squall lines and tropical cyclones.

Aviation Meteorology

The Observatory's Airport Meteorological Office (AMO) at the Hong Kong International Airport provides weather services for civil aviation. The AMO is responsible for the provision of weather services for a designated airspace over the northern part of the South China Sea. It keeps a close watch on the weather and issues warnings on hazardous weather over this airspace. It also runs a web-based automatic information service to provide aviation users with the latest flight documents, aerodrome forecasts and warnings, supplemented by other information such as radar and satellite pictures. Weather briefings are provided to pilots and other aviation users as needed. The Observatory is conducting trials to downlink weather observations made on board aircraft and is studying the feasibility of providing more weather information to aircraft in flight.

    A light detection and ranging system (LIDAR) was installed at the airport in mid-2002 to detect windshear in fine weather. Windshear around the approaches to the airport in rainy weather is kept under close surveillance by the terminal Doppler weather radar at Tai Lam Chung.

Radiation Measurement and Assessment

The Observatory operates an environmental radiation monitoring programme to monitor radiation levels in Hong Kong. The programme entails the measurement of samples of air, water, soil and food collected regularly at several sites. A network of stations monitors the ambient gamma dose rate continuously and warns of any deviation from normal levels. Data are disseminated to the media daily, and published in monthly bulletins as well as in annual reports.

    In an emergency, the Observatory will intensify radiation monitoring by deploying radiological survey teams to monitor radiation levels over Hong Kong. The radiological and meteorological information will be collectively assessed to estimate the transport, dispersion and deposition of any radioactivity over Hong Kong. Based on such assessment, the Observatory will provide technical advice to the Government on appropriate protective actions.

Climatological, Oceanographic and Geophysical Services

Climatological information has applications in activities ranging from recreation through engineering design and environmental impact analysis to litigation. To meet the demand for such information, the Hong Kong Observatory operates a climatological information service. The data available include surface and upper-air observations from Hong Kong and neighbouring countries, marine weather observations from Voluntary Observing Ships and tidal observations.

    The Observatory produces an annual tide table for Hong Kong. It also provides assessments of the probabilities of occurrence of extreme storm surges and advice on oceanographic matters to other government departments and the engineering community.

    To monitor earthquake activities in the vicinity of Hong Kong, the Observatory operates a network of eight short-period seismograph stations. Long-period seismographs at the Observatory's headquarters detect tremors world-wide and information on significant tremors is made public through the media. In addition, three strong motion accelerographs were installed on different geological sites. On average, Hong Kong experiences two to three minor earth tremors every year.

    The Hong Kong Time Standard is provided by a caesium beam atomic clock. Accuracy within fractions of a microsecond a day is maintained. A six-pip time signal is sent to Radio Television Hong Kong for broadcast at quarter-hour intervals. The time checking service is also available to the public through the Observatory's Telephone Information Enquiry System as well as through a Network Time Service at its home page. The Network Time Service provided over 155 million checks in 2002, or about 420 000 checks per day on average. Members of public can make use of this service, with the installation of the appropriate software, to synchronise the clock on their personal computers.

Home Pages

Environment, Transport and Works Bureau: http://www.etwb.gov.hk

Economic Development and Labour Bureau: http://www.edlb.gov.hk

Agriculture, Fisheries and Conservation Department: http://www.afcd.gov.hk

Environmental Protection Department: http://www.epd.gov.hk

Hong Kong Observatory: http://www.hko.gov.hk