ABSTRACT

Accurate estimates of momentum flux through the air-sea interface at very high wind speeds are important for predicting tropical cyclone intensities. To estimate the air-sea momentum flux under the long-fetch condition (20 m fetch) at very high wind speeds using a laboratory tank, a simple momentum flux measurement method using only four water-level gauges is conducted based on the momentum budget method. The air-water momentum flux under long-fetch conditions at very high wind speeds was measured in a typhoon simulation tank at the Research Institute of Applied Mechanics, Kyushu University. The verification was performed using previous values estimated by the eddy correlation method in a typhoon simulation tank at Kyoto University, Japan. The results showed good correlation between the values of momentum flux measured by the present momentum budget method and the other methods. The drag coefficient at very high wind speeds (41 m/s) under long-fetch conditions leveled off, as well as under the short-fetch condition (4.5 m and 6.5 m fetch). Moreover, a very weak relationship was found between the drag coefficient and the fetch. Since the maximum fetch in the present laboratory experiments is 20 m, the future field observation with the longer fetch condition will be needed for applying the results to oceans.

摘要

准确估计极高风速下通过海气界面的动量通量对于预测热带气旋强度非常重要。为了利用实验室水箱估算高风速长取条件（20 m取）下的海气动量通量，基于动量预算法，采用仅使用四个水位计的简单动量通量测量方法。在九州大学应用力学研究所的台风模拟池中测量了极高风速下长取条件下的空气-水动量通量。验证是使用日本京都大学台风模拟池中涡流相关法估计的先前值进行的。结果表明，本动量预算法测得的动量通量值与其他方法测得的动量通量值之间具有良好的相关性。在长取条件下以及短取条件（4.5 m 和 6.5 m 取）下，极高风速（41 m/s）下的阻力系数趋于平稳。此外，发现阻力系数和回弹之间的关系非常弱。由于目前实验室实验的最大取值是20 m，未来需要更长取值条件的现场观测才能将结果应用于海洋。发现阻力系数和回弹之间的关系非常弱。由于目前实验室实验的最大取值是20 m，未来需要更长取值条件的现场观测才能将结果应用于海洋。发现阻力系数和回弹之间的关系非常弱。由于目前实验室实验的最大取值是20 m，未来需要更长取值条件的现场观测才能将结果应用于海洋。