Measuring short‐period wind waves in a tidally forced environment with a subsurface pressure gauge
Measuring short‐period wind waves in a tidally forced environment with a subsurface pressure gauge
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用地下压力计测量潮汐强迫环境中的短周期风波
DOI：
10.4319/lom.2007.5.317
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
S. Monismith
中科院分区：
文献类型：
--
作者：
N. Jones;S. Monismith
研究了配备标准压力传感器的流速计在潮汐力作用下的河口环境中估计欠发达、取量受限波（峰值周期约为2 s）的波谱的能力。这种类型的仪器被放置在整个2.5米水柱的四个高度，并与一个共同定位的电容波计同步记录数据。线性波理论被发现足以描述在频谱的较低频率部分（<0.6 Hz）的波场。电容测波仪的数据显示，频谱的平衡范围可以用λ-4来模拟。最佳截止频率（超过该频率时应用100 - 4模型）被定义为压力谱是本底噪声的12倍但至少是峰值频率的1.1倍的位置。使用这些标准，压力传感器测量的均方根波高和平均波周期的不确定度分别为0.035 m和0.13 s（95%置信水平）。在压力谱的变换中应用电流的点测量被发现与应用垂直平均电流一样可靠。使用的标准发现，以最好地估计波的频谱，一个表达式，确定的压力传感器的能力，以测量波场的利益。该表达式使用户能够指定某个地点的风速和峰值波频率，并确定可以放置压力计的水面以下的最大深度。
The ability of a current meter equipped with a standard pressure sensor to estimate the wave spectra of underdeveloped, fetch‐limited waves (peak period ~2 s) in a tidally forced, estuarine environment was investigated. Instruments of this type were placed at four heights throughout the 2.5 m water column, and data were recorded synchronously with a co‐located capacitance wave gauge. Linear wave theory was found to adequately describe the wave field in the lower frequency portion of the spectra (<0.6 Hz). The capacitance wave gauge data revealed that the equilibrium range of the spectrum could be modeled as ƒ−4. Large variability in the noise floor of the identical pressure gauges was found. The optimal cutoff frequency (beyond which the ƒ−4 model was applied) was defined as the location where the pressure spectra was 12 times the noise floor but was at least 1.1 times the peak frequency. Using these criteria, the pressure sensors measured root‐mean‐squared wave heights and mean wave periods with an uncertainty of 0.035 m and 0.13 s, respectively (95% confidence level). Applying a point measurement of the current in the transformation of the pressure spectra was found to be as reliable as applying a vertically averaged current. Using the criteria found to best estimate the wave spectra, an expression that determines the ability of a pressure sensor to measure the wave field of interest was developed. This expression enables the user to specify the wind velocity and peak wave frequency at a site and determine the maximum depth below the water surface at which the pressure gauge can be placed.