基于实测资料的南海北部台风“海鸥”致近惯性振荡研究
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摘要
文章利用2014年9月南海东北部附近海域的A、B两个相距约20km的潜标数据,分析了台风"海鸥"在南海东北部激发的近惯性振荡的垂向分布特征。结果表明,台风过境在两站点激发了强烈的近惯性振荡,其能量由海表向海洋内部传播;近惯性能量在表层随着深度增加而增大,最大值出现在次表层,此后随着深度增加迅速衰减。但是两个观测站点的近惯性振荡垂向分布特征有较大的差别:A站点的近惯性振荡在不同深度上存在三个不同的垂向相速度,而B站点的垂向相速度没有变化;两站点的最大近惯性动能的大小及其所在深度不同,B站点比A站点的最大近惯性动能大15%左右。台风过后两个站点均出现由近惯性波f和半日内潮波D_2非线性相互作用产生的次级波动fD_2,但其强度存在差异。台风后A站点fD_2在不同深度上有不同的变化,f和D_2相互作用较弱;而B站点的fD_2在整个近惯性振荡影响深度内都是增强,其fD_2和f频带的动能和流速在时空分布以及变化趋势上有较好的相关性。两站点的近惯性振荡垂向相速度以及次级波动fD_2的不同可能是水体层结的差异和涡旋的影响所导致的。
In this study,the vertical characteristics of near-inertial oscillations(NIOs)induced by Typhoon Kalmaegi are analyzed by using data from two moorings about 20 km apart in the northeastern South China Sea in Sept.2014.The results show that the energy of typhoon-induced NIOs,which propagates downward into the ocean interior,increases with depth in the upper layer and becomes maximum in the mid layer before dissipating with depth.However,we find that there is a large difference in vertical characteristics of typhoon-induced NIOs between the two moorings.The NIOs at mooring A had three different vertical phase velocities at different depths while the NIOs at mooring B showed invariable phase velocity.The value and depth of the maximum near-inertial kinetic energy(NIKE)are also different at the two moorings.The maximum NIKE was 15%greater at mooring B than at mooring A.After the passage of Kalmaegi,fD_2 via nonlinear wave interaction between f and D_(2 )occurred at the two moorings,except that the intensities of fD_2 at the two moorings were different.At mooring A,fD_2changed with depth and its interaction between f and D_(2 )was weak.The energy of fD_(2 )at mooring B enhanced at the full depth,and the kinetic energy and velocities of fD_(2 )and f had a good correlation for their time-space distributions and variations.The difference of vertical phase velocity of NIOs and fD_(2 )at the two moorings may be caused by the effects of eddy and different stratifications.
In this study,the vertical characteristics of near-inertial oscillations(NIOs)induced by Typhoon Kalmaegi are analyzed by using data from two moorings about 20 km apart in the northeastern South China Sea in Sept.2014.The results show that the energy of typhoon-induced NIOs,which propagates downward into the ocean interior,increases with depth in the upper layer and becomes maximum in the mid layer before dissipating with depth.However,we find that there is a large difference in vertical characteristics of typhoon-induced NIOs between the two moorings.The NIOs at mooring A had three different vertical phase velocities at different depths while the NIOs at mooring B showed invariable phase velocity.The value and depth of the maximum near-inertial kinetic energy(NIKE)are also different at the two moorings.The maximum NIKE was 15%greater at mooring B than at mooring A.After the passage of Kalmaegi,fD_2 via nonlinear wave interaction between f and D_(2 )occurred at the two moorings,except that the intensities of fD_2 at the two moorings were different.At mooring A,fD_2changed with depth and its interaction between f and D_(2 )was weak.The energy of fD_(2 )at mooring B enhanced at the full depth,and the kinetic energy and velocities of fD_(2 )and f had a good correlation for their time-space distributions and variations.The difference of vertical phase velocity of NIOs and fD_(2 )at the two moorings may be caused by the effects of eddy and different stratifications.
引文
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WANG GUIHUA,SU JILAN,DING YIHUI,et al,2007.Tropical cyclone genesis over the South China Sea[J].Journal of Marine Systems,68(3-4):318-326.
郭琳,宫辉力,朱锋,等,2014.基于小波分析的地下水水位与降水的周期性特征研究[J].地理与地理信息科学,30(2):35-38.GUO LIN,GONG HUILI,ZHU FENG,et al,2014.Cyclical characteristics of groundwater level and precipitation based on wavelet analysis[J].Geography and Geo-Information Science,30(2):35-38(in Chinese with English abstract).
毛华斌,陈桂英,尚晓东,等,2013.西沙海域内潮与近惯性内波的相互作用[J].地球物理学报,56(2):592-600.MAOHUABIN,CHEN GUIYING,SHANG XIAODONG,et al,2013.Interaction between internal tides and near-inertial waves at Xisha area[J].Chinese Journal of Geophysics,56(2):592-600(in Chinese with English abstract).
孙璐,王东晓,胡建宇,等,2008.南海北部海洋对局地生成热带气旋的响应[J].热带海洋学报,27(4):10-18.SUN LU,WANG DONGXIAO,HU JIANYU,et al,2008.Responses of upper layer of northern South China Sea to two locally-generated tropical cyclones[J].Journal of Tropical Oceanography,27(4):10-18(in Chinese with English abstract).
汪胜波,2011.功率谱估计在宽带ADCP信号检测中的研究与应用[D].青岛:中国海洋大学.WANG SHENGBO,2011.Research on power spectrum and its application in broadband ADCP signal detection[D].Qingdao:Ocean University of China(in Chinese with English abstract).
ALFORD M H,2003.Redistribution of energy available for ocean mixing by long-range propagation of internal waves[J].Nature,423(6936):159-162.
ALFORD M H,CRONIN M F,KLYMAK J M,2011.Annual cycle and depth penetration of wind-generated near-inertial internal waves at ocean station papa in the Northeast Pacific[J].Journal of Physical Oceanography,42(6):889-909.
BROOKS D A,1983.The wake of hurricane Allen in the western gulf of Mexico[J].Journal of Physical Oceanography,13(1):117-129.
CHEN GENGXIN,XUE HUIJIE,WANG DONGXIAO,et al,2013.Observed near-inertial kinetic energy in the northwestern South China Sea[J].Journal of Geophysical Research,118(10):4965-4977.
FU L L,1981.Observations and models of inertial waves in the deep ocean[J].Reviews of Geophysics,19(1):141-170.
GUAN SHOUDE,ZHAO WEI,HUTHNANCE J,et al,2014.Observed upper ocean response to typhoon Megi(2010)in the Northern South China Sea[J].Journal of Geophysical Research,119(5):3134-3157.
LIU JUNLIANG,CAI SHUQUN,WANG SHENGAN,2011.Observations of strong near-bottom current after the passage of Typhoon Pabuk in the South China Sea[J].Journal of Marine Systems,87(1):102-108.
LIU JUNLIANG,HE YINGHUI,WANG DONGXIAO,et al,2015.Observed enhanced internal tides in winter near the Luzon Strait[J].Journal of Geophysical Research,120(10):6637-6652.
PARK J H,ANDRES M,MARTIN P J,et al,2006.Second-mode internal tides in the East China Sea deduced from historical hydrocasts and a model[J].Geophysical Research Letters,33(5):L05602.
PRICE J F,1981.Upper ocean response to a hurricane[J].Journal of Physical Oceanography,11(2):153-175.
SHAY L K,ELSBERRY R L,1987.Near-inertial ocean current response to hurricane Frederic[J].Journal of Physical Oceanography,17(8):1249-1269.
WANG GUIHUA,SU JILAN,DING YIHUI,et al,2007.Tropical cyclone genesis over the South China Sea[J].Journal of Marine Systems,68(3-4):318-326.