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1.
During the South China Sea monsoon experiment (SCSMEX),three autonomous temperature line acquisition system (ATLAS) buoys with acoustic Doppler current profiler (ADCP) were moored in the South China Sea to measure temperature,salinity and current velocity.Typhoon Faith passed through about 250 km south to one of the mooring buoys located at 12 58.5 N,114 24.5 E from December 11 to 14,1998.The data analysis indicates that the typhoon winds induce a great increase in the kinetic energy at near-inertial frequencies with two maxima in the mixed layer and thermocline.The near-inertial oscillations were observed at the upper 270 m in the wake of Typhoon Faith.The oscillations were originally excited in the sea surface layer and propagated downward.The amplitudes of the oscillations decrease with depth except in the thermocline.The near-inertial oscillation signals are also remarkable in temperature and salinity fields.  相似文献   

2.
The near-inertial waves (NIWs) are important for energy cascade in the ocean. They are usually significantly reinforced by strong winds, such as typhoon. Due to relatively coarse resolutions in contemporary climate models, NIWs and associated ocean mixing need to be parameterized. In this study, a parameterization for NIWs proposed by Jochum in 2013 (J13 scheme), which has been widely used, is compared with the observations in the South China Sea, and the observations are treated as model outputs. Under normal conditions, the J13 scheme performs well. However, there are noticeable discrepancies between the J13 scheme and observations during typhoon. During Typhoon Kalmaegi in 2014, the inferred value of the boundary layer is deeper in the J13 scheme due to the weak near-inertial velocity shear in the vertical. After typhoon, the spreading of NIWs beneath the upper boundary layer is much faster than the theoretical prediction of inertial gravity waves, and this fast process is not rendered well by the J13 scheme. In addition, below the boundary layer, NIWs and associated diapycnal mixing last longer than the direct impacts of typhoon on the sea surface. Since the energy dissipation and diapycnal mixing below the boundary layer are bounded to the surface winds in the J13 scheme, the prolonged influences of typhoon via NIWs in the ocean interior are missing in this scheme. Based on current examination, modifications to the J13 scheme are proposed, and the modified version can reduce the discrepancies in the temporal and vertical structures of diapycnal mixing.  相似文献   

3.
Based on in-situ observation,satellite and reanalysis data,responses of the western North Pacific subtropical ocean(WNPSO)to the slow-moving category 5 super typhoon Nanmadol in 2011 are analyzed.The dynamical response is dominated by near-inertial currents and Ekman currents with maximum amplitude of 0.39m/s and 0.15m/s,respectively.The near-inertial currents concentrated around 100m below the sea surface and had an e-folding timescale of 4 days.The near-inertial energy propagated both upward and downward,and the vertical phase speed and wavelength were estimated to be 5m/h and 175m,respectively.The frequency of the near-inertial currents was blue-shifted near the surface and redshifted in ocean interior which may relate to wave propagation and/or background vorticity.The resultant surface cooling reaches-4.35℃ and happens when translation speed of Nanmadol is smaller than 3.0m/s.When Nanmadol reaches super typhoon intensity,the cooling is less than 3.0℃ suggesting that the typhoon translation speed plays important roles as well as typhoon intensity in surface cooling.Upwelling induced by the slow-moving typhoon wind leads to typhoon track confined cooling area and the right-hand bias of cooling is slight.The mixed layer cooling and thermocline warming are induced by wind-generated upwelling and vertical entrainment.Vertical entrainment also led to mixed layer salinity increase and thermocline salinity decrease,however,mixed layer salinity decrease occurs at certain stations as well.Our results suggest that typhoon translation speed is a vital factor responsible for the oceanic thermohaline and dynamical responses,and the small Mach number(slow typhoon translation speed)facilitate development of Ekman current and upwelling.  相似文献   

4.
基于锚碇观测资料,本文分析了南海西北部陆坡区上层海洋对台风“杜苏芮”的动力学和热力学响应特征。在动力学响应方面,台风“杜苏芮”期间上层流速显著增强,混合层纬向流速可达1.20 m/s;“杜苏芮”经过后上层海水运动以近惯性振荡为主(流向顺时针旋转周期在36～40 h之间)。近惯性能量在垂向分布上存在两个高值中心,分别位于混合层和温跃层深度上。近惯性能量耗散过程的e折时间尺度约为3.7 d,我们认为能量的向下传播在局地近惯性能量衰减过程中起主要作用。对能量谱的分析表明,“杜苏芮”作用期间近惯性频率能量相对于其作用前增大了约29.4倍,而全日和半日频率(K1和M2)能量有所减弱。此外,能量谱显示近惯性频率存在明显的“蓝移”现象,即对于纬向和经向流速分量在400 m以浅平均的近惯性振荡频率分别为1.167 f0和1.170 f0(f0为局地惯性频率)。蓝移与近惯性内波的向下传播及正的相对涡度的输入有关。在热力学响应方面,上层海洋在台风的搅拌作用下,40～250 m深度均出现较小增温,最大增温幅度接近1°C;此外70 m以浅盐度的降低可能与台风过境时的降水相关,而Ekman抽吸引起的上升流则可能对70～100 m深度盐度的升高具有重要作用。  相似文献   

5.
Many typhoons pass through the East China Sea(ECS) and the oceanic responses to typhoons on the ECS shelf are very energetic. However, these responses are not well studied because of the complicated background oceanic environment. The sea surface temperature(SST) response to a severe Typhoon Rananim in August 2004 on the ECS shelf was observed by the merged cloud-penetrating microwave and infrared SST data. The observed SST response shows an extensive SST cooling with a maximum cooling of 3°C on the ECS shelf and the SST cooling lags the typhoon by about one day. A numerical model is designed to simulate the oceanic responses to Rananim.The numerical model reasonably simulates the observed SST response and thereby provides a more comprehensive investigation on the oceanic temperature and current responses. The simulation shows that Rananim deepens the ocean mix layer by more than 10 m on the ECS shelf and causes a cooling in the whole mixed layer. Both upwelling and entrainment are responsible for the cooling. Rananim significantly deforms the background Taiwan Warm Current on the ECS shelf and generates strong Ekman current at the surface. After the typhoon disappears, the surface current rotates clockwise and vertically, the current is featured by near inertial oscillation with upward propagating phase.  相似文献   

6.
Satellite-derived sea surface temperature (SST) is validated based on in-situ data from the East China Sea (ECS) and western North Pacific where most typhoons, which make landfall on the Korean peninsula, are formed and pass. While forecasting typhoons in terms of intensity and track, coupled ocean-typhoon models are significantly influenced by initial ocean condition. Potentially, satellite-derived SST is a very useful dataset to obtain initial ocean field because of its wide spatial coverage and high temporal resolution. In this study, satellite-derived SST from various sources such as Tropical Rainfall Measuring Mission Microwave Imager (TMI), Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) and New Generation Sea Surface Temperature for Open Ocean (NGSST-O) datasets from merged SSTs were compared with in-situ observation data using an indirect method which is using near surface temperature for validation of satellite derived SST. In-situ observation data included shipboard measurements such as Expendable Bathythermograph (XBT), and Conductivity, Temperature, Depth (CTD), and Argo buoy data. This study shows that in-situ data can be used for microwave derived SST validation because homogeneous features of seawater prevail at water depths of 2 m to 10 m under favorable wind conditions during the summer season in the East China Sea. As a result of validation, root-mean-square errors (RMSEs) are shown to be 0.55 °C between microwave SST and XBT/CTD data mostly under weak wind conditions, and 0.7 °C between XBT/CTD measurement and NGSST-O data. Microwave SST RMSE of 0.55 °C is a potentially valuable data source for general application. Change of SST before and after typhoon passing may imply strength of ocean mixing due to upwelling and turbulent mixing driven by the typhoon. Based on SST change, ocean mixing, driven by Typhoon Nari, was examined. Satellite-derived SST reveals a significant SST drop around the track immediately following the passing of Typhoon Nari in October, 2007.  相似文献   

7.
In September 2011, Typhoon Nesat passed over a moored array of instruments recording current and temperature in the northern South China Sea（SCS）. A wake of baroclinic near-inertial waves（NIWs） commenced after Nesat passed the array. The associated near-inertial currents are surface-intensified and clockwise-polarized. The vertical range of NIWs reached 300 m, where the vertical range is defined as the maximum depth of the horizontal near-inertial velocity 5 cm/s. The current oscillations have a frequency of 0.709 9 cycles per day（cpd）, which is 0.025 f higher than the local inertial frequency. The NIWs have an e-folding time-scale of 10 d based on the evolution of the near-inertial kinetic energy. The depth-leading phase of near-inertial currents indicates downward group velocity and energy flux. The estimated vertical phase velocity and group velocity are 0.27 and 0.08 cm/s respectively, corresponding to a vertical wavelength of 329 m. A spectral analysis reveals that NIWs act as a crucial process to redistribute the energy injected by Typhoon Nesat. A normal mode and an empirical orthogonal function analysis indicate that the second mode has a dominant variance contribution of 81%, and the corresponding horizontal phase velocity and wavelength are 3.50 m/s and 420 km respectively. The remarkable large horizontal phase velocity is relevant to the rotation of the earth, and a quantitative analysis suggests that the phase velocity of the NIWs with a blue-shift of 0.025 f overwhelms that of internal gravity waves by a factor of 4.6.  相似文献   

8.
Near inertial motion excited by wind change in a margin of the Typhoon 9019   总被引：1，自引：0，他引：1  
An excitation of inertial oscillation in the upper layer east of course of Typhoon 9019 was fortuitously observed at three surface buoys deployed during the Ocean Mixed Layer Experiment (OMLET). The observed inertial oscillation was compared with wind fluctuation measured at Ocean Weather Station T (29°N, 135°E) which was placed at the center of a triangle with three vertexes occupied by the respective surface buoys. Inertial oscillation is effectively excited in the mixed layer at the eastern margin of the typhoon by a rapid decrease of wind rather than by prevailing strong wind. It is shown by means of a least square deviation that the inertial oscillation observed in the mixed layer has a period of 23.9 hours shorter than the local inertial period of 24.7 hours. This shorter period suggests that the inertial oscillation has the finite velocities of phase and group as an inertial internal wave. A theoretically obtained ratio of vertical component of group velocity to that of phase velocity, approximately agrees with observed value. The inertial internal wave is excited by fluctuation of divergence with near inertial period in the mixed layer.  相似文献   

9.
On the basis of the time series observations from a temperature chain and an acoustic Doppler current profiler on the continental shelf of the northern South China Sea, a sequence of internal solitary waves （ISWs） and background waves （BWs, including internal tides and near-inertial waves） on the continental shelf were captured simultaneously after the transit of Typhoon Neast in October 2011. These measurementsprovided a unique opportunity to explore the influence of BWs on the ISWs. The BWs appeared a conversion on the current strength and vertical mode structure during the observational period. The BWs were dominated by weak and mode-one waves before October 2 and then turned to strong and high-mode waves after that time. Meanwhile, the ISWs displayed different wave structures before and after October 2, which was closely related to BWs＇ changes. According to the current profiles of BWs, the high-mode wave structure with strong current could significantly strengthen the vertical shear of ISWs in the near-surface layer and promote the breaking of ISWs, and thus it may play an important role in affecting the background current condition.  相似文献   

10.
潮汐作用下渤海温跃层波动与起伏的数值研究   总被引：1，自引：0，他引：1  
研究了潮汐(四大分潮 M2,S2,K1,O1同时输入)作用下渤海温跃层起伏与波动的三维数值模型(将海洋分为3层,即上混和层、跃层和下混和层),揭示了整个海区温跃层上界面处跃层起伏(在文中指每个时刻跃层波高的周期平均值)的地理分布及叠加在起伏之上的潮周期波动的时空变化,模拟出跃层波动与实测基本一致.结果发现大振幅的跃层波动均发生在海峡及近海地形突变之处.一般界面波动的波高大于甚至远远大于同一位置的表层潮波.从位相以及周期来看,潮波和跃层上下界面波动相互之间,有些海域一致,有些地方则相差甚远.跃层上界深度及厚度的梯度,对跃层起伏分布有一定的影响.跃层起伏还可能与海岸海底摩擦有关.  相似文献   

11.
利用Argo剖面浮标分析上层海洋对台风“布拉万”的响应   总被引：9，自引：2，他引：7  
In situ observations from Argo profiling floats combined with satellite retrieved SST and rain rate are used to investigate an upper ocean response to Typhoon Bolaven from 20 through 29 August 2012. After the passage of Typhoon Bolaven, the deepening of mixed layer depth(MLD), and the cooling of mixed layer temperature(MLT) were observed. The changes in mixed layer salinity(MLS) showed an equivalent number of increasing and decreasing because the typhoon-induced salinity changes in the mixed layer were influenced by precipitation, evaporation, turbulent mixing and upwelling of thermocline water. The deepening of the MLD and the cooling of the MLT indicated a significant rightward bias, whereas the MLS was freshened to the left side of the typhoon track and increased on the other side. Intensive temperature and salinity profiles observed by Iridium floats make it possible to view response processes in the upper ocean after the passage of a typhoon. The cooling in the near-surface and the warming in the subsurface were observed by two Iridium floats located to the left side of the cyclonic track during the development stage of the storm, beyond the radius of maximum winds relative to the typhoon center. Water salinity increases at the base of the mixed layer and the top of the thermocline were the most obvious change observed by those two floats. On the right side of the track and near the typhoon center when the typhoon was intensified, the significant cooling from sea surface to a depth of 200×104 Pa, with the exception of the water at the top of the thermocline, was observed by the other Iridium float. Owing to the enhanced upwelling near the typhoon center, the water salinity in the near-surface increased noticeably. The heat pumping from the mixed layer into the thermocline induced by downwelling and the upwelling induced by the positive wind stress curl are the main causes for the different temperature and salinity variations on the different sides of the track. It seems that more time is required for the anomalies in the subsurface to be restored to pretyphoon conditions than for the anomalies in the mixed layer.  相似文献   

12.
南海西北陆坡区内潮与近惯性内波观测研究   总被引：2，自引：2，他引：0  
梁辉  郑洁  田纪伟 《海洋学报》2016,38(11):32-42
通过对2006年南海西北部海域近3个月的全水深流速观测资料的分析,研究了该海区正压潮、内潮及近惯性内波的时空分布特征。结果表明,全日内潮明显强于半日内潮,且最大潮流均出现在海洋上层;内潮的主轴方向基本沿东南-西北方向,近似与局地等深线垂直;内潮能量显示出明显的时间长度约为半月的大小潮调制周期;全日内潮的coherent部分占全日内潮能量的70%,而半日内潮的coherent部分占半日内潮能量的53%;进一步研究发现半日内潮主要由第一模态主导,而全日内潮第三模态能量占总能量的比例仅次于第一模态且量值上与之相当;强风过程可激发出强的近惯性运动,暖涡使得近惯性内波能量更有效地向海洋深层传播,冷涡则不利于近惯性内波能量向下传播。  相似文献   

13.
Ocean temperature responses to Typhoon Mstsa in the East China Sea   总被引：1，自引：1，他引：0  
The MASNUM wave-tide-circulation coupled model, with 21 layers in the vertical and （1/8） °horizontal resolution, was employed to investigate the oceanic responses to Typhoon Mstsa which traversed the East China Sea （ECS） during the period of 4 - 6 August, 2005. Numerical experiment results are analyzed and compared with observation. The responses of the sea surface temperature （SST）, in a focused area of （27° -29°N, 121° - 124°E）, include heating and cooling stages. The heating is mainly due to warm Kuroshio water transportation and downwelling due to the water accumulation. In the cooling stage, the amplitude of the simulated cold wake （ -3℃ ）, located on the right side of this typhoon track, is compared quite well with that of the satellite observed SST data. The wave-induced mixing（Bv） plays a key role for the SST cooling. Bv still plays a leading role, which accounts for 36%, for the ocean temperature drop in the upper ocean of 0 - 40 m, while the upwelling is responsible for 84% of the cooling for the lower layer of 40 - 70 m. The mixed layer depth （MLD） increased quickly from 28 to 50 m in the typhoon period. However, the simulated MLD without the wave-induced vertical mixing, evolution from 13 to 32 m, was seriously underestimated. The surface wave is too important to be ignored for the ocean responses to a typhoon.  相似文献   

14.
基于南海北部浮标和潜标的声学多普勒流速剖面仪（ADCP）数据,通过一套几何算法计算了台风海鸥（1415）期间ADCP的空间变化和流速误差,并进行数据校正。浮标上,台风过后ADCP的水平位移最大可达2.61 km,水平流速误差最大可达0.27 m/s,垂向流速误差最大仅为5×10-4 m/s;温跃层流速校正值在台风过后显著大于流速测值,这表明水平校正对于温跃层流速的质量控制很重要。潜标上,ADCP最大垂向位移增量为179 m,最大绳子倾角为35°,最大水平位移为1.5 km; ADCP水平流速误差和倾角误差都很小,在数据校正中可忽略不计,但对台风过后中层流速的垂向校正不能忽略。  相似文献   

15.
利用SeaWiFS及NOAA卫星资料,基于均值合成算法,分析了"百合"台风对海表温度(SST)、海表叶绿素a浓度及海水透明度的影响,结果表明,整个研究海域(22°～30°N、121°～131°E)的平均SST从台风前的25.48℃下降到22.45℃,平均下降幅度为12.95%.在台风盘旋的中心区域(26°～28°N、123°～127°E),SST平均下降了5.40℃,下降幅度达21.20%,SST下降最大的是9月14日,整个研究海域平均SST仅为13.48℃.整个研究海域海表叶绿素a浓度在台风期间有较大的增加,从台风前的0.425 mg/m3(平均值)上升到0.537 mg/m3,平均增长26.35%.除浙江近海外,台风核心区域海表叶绿素a浓度增幅最大,达1.695倍,表明台风风力越强,台风停留时间越长,对海表叶绿素a浓度增加的贡献就越大.这一增加有利于海洋生物的生长,有利于提高初级生产力和改善海洋生态环境.在"百合"台风期间,海水透明度却有一定程度的降低,从台风前的16.84 m(平均值)下降至台风后的12.67 m,平均降幅为24.76%,降幅最大的是24°～26°N、125°～127°E区块,平均下降了7.96 m,降幅高达47.6%;总体上台风核心区域南部的海水透明度降幅大于区域北部,台风核心区域东南部的海表叶绿素a浓度增幅大于区域东北部.同时,对整个研究海域分割成2°×2°大小的区块,以每个区块的海表叶绿素a浓度、SST和海水透明度的均值代表该区块的值,对台风前、后海表叶绿素a浓度、SST和海水透明度的变化进行相关性分析,发现海表叶绿素a浓度的变化与SST和海水透明度均呈负相关性,且台风期间海表叶绿素a浓度增加的百分比与相应区块海水透明度下降的百分比之间的相关系数达0.821.  相似文献   

16.
A surface buoy was moored from 20 April to 2 November 1988 at 28°48 N and 135°01 E where the water depth was 4900 m to measure temperature and velocity in the upper 150 m. The Typhoon 8824 passed at 0300 (JST) on 8 October about 50 km north to the mooring station with a maximum wind speed of 43.5 m s–1. The buoy was shifted about 30 km to southwest, and the instruments were damaged. The records of temperature at 0.5 m and velocity at 50 m were obtained. The inertial oscillation caused by the typhoon is described using the current record. The oscillation endured for about 20 days. Deep mixing and vertical, heart transport by the typhoon are discussed based on the data from the Ocean Data Buoy of the Japan Meteorological Agency moored at 29°N and 135°E.  相似文献   

17.
Temperature field in the vicinal area of station T (29N, 135E) before and after Typhoon 6411 in summer 1964 is analysed from measurements with BT. At a location 68 km distant from the path of the typhoon, temperature at each depth became lower in the upper layer from surface to 50 m deep and became higher in the lower layer from 50 m to 130 m deep in connection with passage of the typhoon than temperature at each depth in these layers before the typhoon, respectively. Heat loss in the upper layer and heat gain in the lower layer are estimated to be almost comparable in amount. Equivalence in the heat gain and loss suggests that temperature changes were caused by vertical mixing due to strong wind of the typhoon. At a location 164 km distant from the path of the typhoon, however, heat gain of the lower layer from 35 m to 250 m deep exceeded heat loss of the upper layer from surface to 35 m deep. In addition to vertical mixing, horizontal advection or some other processes should be taken into account in order to explain the temperature changes in the area a little distant from the typhoon path. For recovery of the temperature changes at these locations 8 days were needed. This recovery time is almost equal to those in the case of some other typhoons, about which the discussion was made in the previous paper (Maeda, 1965).  相似文献   

18.
2015年9月台风“灿鸿”经过黄海海域的QF111浮标,该浮标观测到黄海海洋的温度和流速响应。受台风影响,黄海海表温度有明显的下降,降温幅度在2~4°C,且在台风路径右侧形成了海表面温度低于20°C的低温斑块。流速的响应主要表现为台风过境期间流速增强,达1.2~1.5 m/s,呈现出全水深强化的特征。风一直对海洋有能量输入,且在台风过境期间风输入海洋的能量最大,旋转功率谱的分析结果表明台风输入海洋的能量向海洋内部传播。黄海海域由台风激发出的近惯性振荡衰减较快,近惯性振荡e折时间尺度约为2 d。  相似文献   

19.
孙凡  于非  司广成  王建丰  唐瑛 《海洋与湖沼》2021,52(5):1125-1136
台风能够对黄海的水文结构及人民群众的生产生活产生重要的影响,严重威胁了人们的生命财产安全。利用ROMS(regional ocean modeling system)模式,分析了台风"灿鸿"在过境黄海期间对黄海温度及环流结构的影响过程。结果表明,台风期间强烈的风致混合能够使温跃层的深度增大,强度减弱,同时,使得近岸的底层温度迅速升高,推动底层的温度锋面向黄海内区移动。台风过境也会对黄海冷水团环流产生重要的影响,台风过境前,混合层中的北向流会迅速加深增强,同时伴随着混合层及温跃层的下移,从而使得黄海冷水团环流的流核下移至跃层以下。当台风过境时,黄海上空的气旋式风场会加剧黄海上层的气旋式环流,导致黄海冷水团环流的流幅及流量迅速增加。当台风登陆后,黄海上层的温度及黄海冷水团环流的结构开始逐渐恢复。  相似文献   

20.
A one-dimentional three-layer model for the thermal structure in the Huanghai Sea is presented in this study, me model consists of the upper mixed layer caused by heating and wind mixing, the lower mixed layer driven by tidal mixing, and the thermocline with certain thickness. The entrainment velocities of the upper and lower layers are obtained respectively. The results show that the model is capable of describing the development and decline processes of the seasonal thermocline in the Huanghai Sea, simulating successfully the Huanghai Sea Cold Water Mass, the nearshore front and surface cold water off North Jiangsu and explaining reasonably their formation mechanisms as well as the strong thermocline off Qingdao. It is suggested that the tidal mixing plays key role in the formation of the nearshore front off North Jiangsu and the strong thermocline off Qingdao. The wind mixing and the tidal mixing make the lower layer water with high nutrients go up to the upper layer. This physical process may be sig  相似文献   

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