| Qi Yongfeng,Shang Xiaodong,Chen Guiying,Yu Linghui. 2020. Eddy covariance measurements of turbulent fluxes in the surf zone. Acta Oceanologica Sinica, 39(3):63－72 |
| Eddy covariance measurements of turbulent fluxes in the surf zone |
| 海浪区湍流通量的涡度协方差观测 |
| Received:July 04, 2019 |
| DOI：10.1007/s13131-020-1562-8 |
| Key words:eddy covariance turbulent fluxes surface gravity waves cospectrum tides |
| 中文关键词: 涡度协方差 湍流通量 表明重力波 协谱 潮汐 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41876023, 41630970 and 41876022; the Instrument Developing Project of the Chinese Academy of Sciences under contract No. YZ201432; the Guangzhou Science and Technology Project under contract No. 201707020037; the National Key R&D Plan of China under contract Nos 2017YFC0305804 and 2017YFC0305904. |
| Author Name | Affiliation | E-mail | | Qi Yongfeng | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | Shang Xiaodong | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | xdshang@scsio.ac.cn | | Chen Guiying | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | | | Yu Linghui | State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China | |
|
| Hits: 2033 |
| Download times: 1309 |
| Abstract: |
| Turbulent eddies play a critical role in oceanic flows. Direct measurements of turbulent eddy fluxes beneath the sea surface were taken to study the direction of flux-carrying eddies as a means of supplementing our understanding of vertical fluxes exchange processes and their relationship to tides. The observations were made at 32 Hz at a water depth of ~1.5 m near the coast of Sanya, China, using an eddy covariance system, which mainly consists of an acoustic doppler velocimeter (ADV) and a fast temperature sensor. The cospectra-fit method-an established semi-empirical model of boundary layer turbulence to the measured turbulent cospectra at frequencies below those of surface gravity waves-was used in the presence of surface gravity waves to quantify the turbulent eddy fluxes (including turbulent heat flux and Reynolds stress). As much as 87% of the total turbulent stress and 88% of the total turbulent heat flux were determined as being at band frequencies below those of surface gravity waves. Both the turbulent heat flux and Reynolds stress showed a daily successive variation; the former peaked during the low tide period and the later peaked during the ebb tide period. Estimation of roll-off wavenumbers, k0, and roll-off wavelengths, λ0 (where λ0=2π/k0), which were estimated as the horizontal length scales of the dominant flux-carrying turbulent eddies, indicated that the λ0 of the turbulent heat flux was approximately double that of the Reynolds stress. Wavelet analysis showed that both the turbulent heat flux and the Reynolds stress have a close relationship to the semi-diurnal and diurnal tides, and therefore indicate the energy that is transported from tides to turbulence. |
| 中文摘要: |
| 湍流涡旋在海流中起关键作用。为了研究海浪区垂向湍流通量交换过程以及其与潮汐的关系，本研究利用一套涡动相关系统在三亚市近海岸海区对海浪区的湍流通量进行了一次直接测量。观测系统主要由一个声学多普勒测速仪（ADV）和一个快速温度传感器组成，数据采集频率为32Hz，测量水深约在海表以下1.5米，时长约为2天。文中采用协谱拟合法计算湍流通量，以去除海表波浪带入的计算误差。协谱拟合法为对观测的湍流协谱在小于表面重力波频段区间与边界层上湍流半经验模型进行拟合对比，求取湍流通量（包括湍流热通量和雷诺应力）。研究表明，87%的雷诺应力和88%的湍流热通量可以由小于表面重力波频段区域计算获得。湍流热通量和雷诺应力都有明显的日变化特征，呈现出热通量在低潮期和雷诺应力在退潮期达到峰值的特征。利用协谱拟合法获取涡旋的截断波数k0和截断波长λ0，其表示涡旋对湍流通量起最大贡献作用的水平空间尺度，表明该研究中湍流热通量的λ0约为雷诺应力对应的λ0的两倍。子波分析显示湍流热通量和雷诺应力与半日潮和全日潮均有密切联系，表明了能量从潮汐向湍流的输运过程。 |
|
HTML
View Full Text
View/Add Comment Download reader |
| Close |
|
|
|
