| Summary: | 碩士 === 國防大學中正理工學院 === 應用物理研究所 === 92 === ABSTRACT
In order to realize the accuracy of low-level wind shear alarms at the CKS and Sungshan Airports and investigate the wind-shear-related weather patterns, the topographic effect and the occurrence of the wind shears associated with the wind direction, wind speed, time duration and turbulence spatial scale, the study elucidates the outputs of the low-level wind shear alert systems (LLWAS) and automated weather observing systems (AWOS) and compares with the recalculated results based upon the recursion operation of velocity divergence in use the raw data measured by the wind towers every 10 seconds which are allocated in the airports (15 wind towers in the CKS Airport and 13 in Sungshan Airport).
The primary findings are: (1) The system outputs at the CKS Airport seem over-estimated in the moderate and severe wind shears from the alarms number and wind shear intensity points of view. However, the system outputs at the Sungshan Airport look under-estimated in the severe wind shears. (2) After more careful examination, the highest frequency of wind shears occurs 10 min prior to the arrival of the frontal system and extends more than 30 min. (3) For intense southwesterlies or well-organized frontal systems, the most possible outcome of wind shears occurs between 280 deg and 290 deg at the Sungshan Airport, probally due to the channel effect induced by the blocking of Lin-kou hill and Guan-yin mountain. (4) It shows that the mature frontal case is capable to extend the life duration of wind shears. Besides, most of the turbulence spatial scales related to wind shears are less than 10 km, resulting in that the wind towers in the airport should be allocated less than 5 km in distance in order to measure low-level wind shears effectively.
Keywords: Low-level Wind Shear, Southwesterly Flow, Mei-yu
Front, Recursion Operation, Velocity Divergence,
Topographic Effect, Channel Effect.
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