Abstract
The measurement and prediction of wind fields have important practical applications. The strong winds associated with severe weather phenomena, such as thunderstorms, tropical cyclones, and tornadoes, may affect the safety and serviceability of buildings and structures. Sudden changes in wind, although not of significantly high magnitudes, may contribute wind shear and turbulence to aircraft operations at airports, causing aircraft to deviate from the intended flight paths and fall to the ground.This thesis presents a comprehensive study of wind structures of severe weather phenomena, which is expected to be useful for wind engineering applications, as well as monitoring and prediction of low-level wind shear and turbulence, with high applicability with respect to structural design and aviation safety. Several measurement cases are presented and analysed, and the performances of numerical weather prediction models are examined by comparison with the actual observations.
To study wind structure and characteristics, it is necessary to conduct accurate measurements of the wind fields near the ground and in the upper atmosphere with high temporal and spatial resolutions. This thesis reviews the state of the art of wind measurements in southern China, namely, the use of wind towers, ground-based remote-sensing meteorological instruments, and aircraft-mounted devices. The operation principles of the equipment are briefly discussed, and the consistency of the measurements is assessed via cross-comparison using long-term field observations.
The wind structures of severe weather phenomena are then analysed and discussed. The 356-m-high meteorological tower in Shenzhen, China, is an useful tool for the study of mean wind and turbulence at high temporal resolutions. The dropsondes are important means for the measurements of the dynamic and thermodynamic profiles of tropical cyclones over oceans. Moreover, the ground-based remote-sensing meteorological instruments, such as acoustic radar, microwave radar, and laser radar, provide valuable upper-air wind records under different types of weather conditions.
In particular, this thesis investigates the vertical wind profiles of waterspouts/tornadoes in southern China, a region where has not been probed before in this aspect. The collected records are expected to be useful to wind engineering applications.
The vertical wind and temperature profiles of tropical cyclones are obtained using microwave radars and dropsondes. The measurement results are critical for the investigation of the strengthening and weakening of tropical cyclones over the South China Sea.
Another important application of wind measurements is the investigation of low-level wind shear and turbulence at the Hong Kong International Airport, which is situated in an area of complex terrain, making the winds rather variable at times. The airport is equipped with various types of state-of-the-art wind measuring equipment. Cases of wind shear are studied, and statistical analysis of winds is conducted. The analysis results can serve as useful references to the operation of the airport in a region with complicated terrain.
The possible forecasting and nowcasting of low-level wind shear and turbulence by large eddy simulation is another major focus aspect in this study. The results show that large eddy simulation has some potential values in the operational forecasting of wind shear and turbulence at airports in real time.
This thesis is expected to provide useful information for researchers and practitioners in the field of wind engineering for structural design, and serve as a research basis in the field of aviation weather forecasting.
The novelties of the present study include the first study of vertical profiles of severe weather in southern China, first dropsonde observational study of tropical cyclones over the northern part of the South China Sea; first systematic documentation and statistical analysis of low level windshear and turbulence at the Hong Kong International Airport, and first application of high resolution numerical models to study wind disturbances at the Hong Kong International Airport due to terrain and buildings.
| Date of Award | 22 Mar 2023 |
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| Original language | English |
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| Supervisor | Qiusheng LI (Supervisor) |