IntroductionOperational Windshear Warning System (OWWS)
Introduction
Windshear was partly blamed for the crash of a CAAC trident aircraft at the Hong Kong Kai Tak International Airport in 1988. The new airport at Chek Lap Kok on Lantau Island, according to consultants' information, has 30 percent more chances of thunderstorm activity than the existing Kai Tak International Airport. In addition, the mountainous terrain south of the site of the new airport together with the prevailing winds occasionally produce severe turbulence which could affect aircraft operations, particularly during takeoffs and landings. While improved aircraft design has overcome most of the traditional weather-related problems such as poor visibility and icing, wind turbulence remains a significant problem.
The Hong Kong University of Science and Technology (HKUST), in partnership with the US-based Weather Information Technologies, Inc. (WITI), the business arm of National Centre for Atmospheric Research (NCAR), has signed a four-year HK$118.7 million contract with the Hong Kong Government to provide a weather monitoring and warning system for the new airport at Chek Lap Kok. The system entitled "Operational Windshear Warning System (OWWS)" will seek to warn pilots of windshear conditions around the new airport, giving pilots valuable lead time to decide how to handle the situation.
Field Research Programme
Activities during the first year of the project, which began in October 1993, were focused on an intensive meteorological field research programme to develop a thorough understanding of air flow patterns over and around Lantau . Automatic weather stations (AWS) and wind profilers were setup at various sites on Lantau and the nearby islands to record wind data.
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One of the automatic weather stations (AWS) installed on Lautau Island. An AWS is designed for long-term climatological monitoring, meteorological research and routine weather measurement applications. Typical meteorologic measurements collects by an AWS include:
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| Wind profiler installed on Waglan Island. A wind profiler is a remote sensing, Doppler radar that can "see" which way the air is moving and how fast it is moving. It is called a "profiler" because it gives air speed and direction data at several different elevations, thus providing a vertical profile of the earth's atmosphere. |  |
The data collected from the field research programme was then analysed by researchers using atmospheric numerical models installed on a high-performance workstation at HKUST and NCAR's Cray Supercomputer. The accuracy of the models was validated by deploying NCAR's custom-fitted Beechcraft Super KingAir B200T for airborne measurements over Lantau Island. Based on information collected from the field research programme, an advanced computer model was to be developed to simulate the air flow over Lantau, and predict occurrences of windshear and turbulence at the new airport site.
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NCAR's Beechcraft Super KingAir B200T for airborne measurements over Lantau. The KingAir was equipped with standard instruments to provide basic meteorological measurements, and special equipment to map the airflow around Lantau and to locate and characterize turbulence and windshear. The KingAir made a total of 94 flights during 18 April, 1994 to 24 November, 1994. |
OWWS
In addition to the primary objective of providing important safety-related weather information to aircraft operating into and out of the new Chek Lop Kok airport, the OWWS has been designed to meet a number of secondary goals including flexibility, simplicity, externsibility, reliability and accuracy.
When operational, the OWWS will integrate data from various sensors and sources, which includes:
Based on the above data, the OWWS will generate the following information to the users:
The OWWS detection information will be displayed in text and/or graphical format which can be easily interpreted by pilots, air traffic controllers, air traffic managers and aviation forecasters. OWWS alerts are given using commonly accepted aeronautical navigation terminology