Directional Wave Spectra Observed During Intense Tropical Cyclones
Directional Wave Spectra Observed During Intense Tropical Cyclones
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DOI：
10.1002/2017jc012943
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发表时间：
2018-02-01
影响因子：
3.6
通讯作者：
Graber, H. C.
中科院分区：
文献类型：
--
作者：
Collins, C. O., III;Potter, H.;Graber, H. C.
在2010年台风季节，两个深海系泊设施被部署在距离台湾南部海岸780公里的地方，为期4-5个月。在强热带风暴电木和三个热带气旋(TCS)--台风Fanapi、超级台风Megi和台风Chaba的接近过程中，在两个极端海气相互作用浮标上记录了方向波谱、风速和风向以及动量通量。采样的条件包括高达11米的显著波高和高达26毫秒(-1)的风速。大尺度光谱结构的细节在频率和方向上有所不同，但大多是双峰的。这些模式一般由来自最强风暴区和局地风海的涌浪系统组成。当风暴接近时，峰值系统一直都很年轻，这意味着受到风的积极推动。在最强烈的航道的顶峰，北部系泊的Chaba和南部的Megi，双峰海合并在一起。在茶坝期间，涌浪和风海耦合将高频波和风应力引向远离风向。光谱波浪模型能够再现定向光谱的许多宏观特征。简而言之，风吹过海洋产生波浪。热带气旋以其旋风模式和极强的风力产生了地球上一些最危险和最复杂的波场。使用浮标测量，在2010年台湾沿海的三个强烈热带气旋的近距离通道中幸存下来，我们查看了这些复杂的波浪场的细节。我们发现，波浪场一般由来自风暴最强区域的长波系统和由局地风产生的短波系统组成。这两个波系经常以不同的方向传播。当风暴过去时，这两个波浪系统有时重叠并合并，有时保持分离。目前还不清楚到底是什么决定了它们是否结合在一起，但这肯定是一个非线性现象。在一次航行中，短波和长波结合在一起改变了短波的方向，而短波又通过改变风应力的方向与大气相互作用。这一结果令人惊讶，可能有助于提高我们模拟热带气旋强度的能力。
Two deep-sea moorings were deployed 780 km off the coast of southern Taiwan for 4-5 months during the 2010 typhoon season. Directional wave spectra, wind speed and direction, and momentum fluxes were recorded on two Extreme Air-Sea Interaction buoys during the close passage of Severe Tropical Storm Dianmu and three tropical cyclones (TCs): Typhoon Fanapi, Super Typhoon Megi, and Typhoon Chaba. Conditions sampled include significant wave heights up to 11 m and wind speeds up to 26 ms(-1). Details varied for large-scale spectral structure in frequency and direction but were mostly bimodal. The modes were generally composed of a swell system emanating from the most intense storm region and local wind-seas. The peak systems were consistently young, meaning actively forced by winds, when the storms were close. During the peaks of the most intense passagesChaba at the northern mooring and Megi at the southernthe bimodal seas coalesced. During Chaba, the swell and wind-sea coupling directed the high frequency waves and the wind stress away from the wind direction. A spectral wave model was able reproduce many of the macrofeatures of the directional spectra.Plain Language Summary Wind blowing over the ocean generates waves. Tropical cyclones, with their cyclonic wind pattern and extremely high winds, generate some of the most dangerous and complex wave fields on the planet. Using buoy measurements, which survived the close passages three intense tropical cyclones off the coast of Taiwan in 2010, we look at the details of these complex wave fields. We found that the wave field is generally made up of a system of longer waves which emanate from the most intense region of the storm and a system of shorter waves which are produced by the local winds. These two wave systems often propagate in different directions. As a storm passes, sometimes these two wave systems overlap and combine and sometimes they remain separate. It is unclear exactly what determines whether or not they combine, but it is certainly a nonlinear phenomenon. During one passage, the short and long seas combined shifting the direction of the short waves, which in turn interacted with the atmosphere by shifting the direction of the wind stress. This result was surprising and may help to improve our ability to model tropical cyclone intensity.