地球科学进展

地球科学进展 ›› 2018, Vol. 33 ›› Issue (3): 270 -280. doi: 10.11867/j.issn.1001-8166.2018.03.0270

研究论文 上一篇    下一篇

南海西边界急流影响下的近惯性振荡特征分析
江森汇 1( ), 吴泽文 2, 舒勰俊 3   
  1. 1.广州航海学院航务工程学院,广东 广州 510725
    2.热带海洋环境国家重点实验室,中国科学院南海海洋研究所,广东 广州 510301
    3.国家海洋局南海规划与环境研究院,广东 广州 510310
  • 收稿日期:2017-11-09 修回日期:2018-02-02 出版日期:2018-03-20
  • 基金资助:
    *2017年广东省高等教育“创新强校工程”建设项目“基于ADCP观测资料的湍流应力特征及其影响机制分析”(编号:E410709)资助.

Characteristics of Near-inertial Oscillation Influenced by Western Boundary Current of South China Sea

Senhui Jiang 1( ), Zewen Wu 2, Xiejun Shu 3   

  1. 1.School of Harbor Engineering, Guangzhou Maritime University, Guangzhou 510725, China
    2.State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
    3.South China Sea Institute of Planning and Environmental Research, State Oceanic Administration, People’s Republic of China, Guangzhou 510310, China;
  • Received:2017-11-09 Revised:2018-02-02 Online:2018-03-20 Published:2018-05-02
  • About author:

    First author:Jiang Senhui(1983- ), male, Taizhou City, Zhejiang Province, Lecturer. Research areas include ocean wave motion and mixing.E-mail:jiangsh_gmi@163.com

  • Supported by:
    Project supported by the Guangdong Higher Education Innovation Strong School Project “The characteristics of the turbulent stress and its influence mechanism based on the ADCP observation data”(No.E410709).
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在利用南海西沙海域多年声学多普勒流速剖面仪(ADCP)观测流速资料分析近惯性内波运动的生成、传播等演变特征的过程中,发现冬季和夏季的近惯性振荡频率存在整体性的偏移效应。ADCP所处海域位于南海西边界急流区,冬季和夏季的背景环流分别为东北向和西南向,背景环流的方向性差异可能影响近惯性振荡频率的偏移效应。针对背景环流的不同方向,筛选出其对应的近惯性振荡信号,进行合成分析,探讨南海西边界急流如何影响近惯性振荡特征。从背景涡度的角度对这一影响机制做出了解释:夏季时,东北方向背景环流的水平剪切使得局地产生负的背景涡度,近惯性振荡频率往低频方向偏移(“红移”现象);冬季时,西南向背景环流的水平剪切导致局地产生正的背景涡度,近惯性振荡频率往高频方向偏移(“蓝移”现象)。

关键词: 近惯性振荡, 偏移效应, 背景环流, 背景涡度

Based on observed velocity data of ADCP for near-inertial wave evolution characteristics of generation and propagation, the difference of shifting effect was found in winter and summer. The background circulation in winter and summer is northeast and southwest, respectively. The diversity of the background flow directions may take an important part in shifting effect of the near-inertial wave motion. According to the different directions of the background circulation, the signals of near-inertial oscillation were screened out and analyzed by synthesis for discussing how the directions of background circulation affected the characteristics of near-inertial oscillation. The mechanism of this effect was explained from the perspective of background vorticity: As the direction of background circulation is the northeast, the background vorticity becomes negative and the effective frequency decreases, the near-inertial oscillation frequency shifts to low frequency band (red shift); contrarily, the background vorticity becomes positive and the effective frequency increases with the southwest background circulation, the near-inertial oscillation frequency shifts to high frequency band (blue shift).

Key words: Near-inertial oscillation, Shifting effect, Background circulation, Background vorticity.

中图分类号: 

图1 潜标位置及台风路径
红色“★”代表潜标观测系统的投放位置,紫色线表示2007—2013年,过境南海西沙海域的热带气旋的行进路径,包括从西太平洋穿过菲律宾进入南海的和南海局地生成的热带气旋
Fig.1 A map of the ADCP mooring station and typhoons’ track
Location of the ADCP mooring station is marked by a red pentagram.Typhoons’ track are labeled by purple full line
表1 潜标系统搭载的ADCP(75 kHz)观测数据概况
Table 1 The survey of data observed by the ADCP mooring system
序号 起始时间 终止时间 经度(E) 纬度(N) 观测水深
/m		 垂向分辨率
/m		 采样间隔
/min
1 2007/08/20 2008/08/21 110.30° 17.11° 35~459 8 60
2 2008/08/22 2009/05/03 110.30° 17.12° 45~461 16 60
3 2009/05/04 2010/09/04 110.39° 17.10° 37~477 8 60
4 2010/09/05 2011/08/23 110.41° 17.13° 137~641 8 60
5 2011/08/24 2012/08/22 110.43° 17.17° 62~542 16 60
6 2012/08/23 2013/12/08 110.42° 17.17° 35~539 8 60
图2 2007—2013年近惯性动能及其标准差
蓝色实线表示观测水深公共段(50~250 m)垂向平均的近惯性振荡动能,其他实线是各观测时间段内各自的垂向平均近惯性振荡动能;“8.7”代表2007—2013年整体观测资料的3倍标准差值,以此来确定近惯性振荡发生的具体时间段;由于观测水深的原因,舍弃了2010年9月至2011年8月的观测数据
Fig.2 Depth-averaged near-inertial kinect energy and its standard deviation from 2007 to 2013
The blue line represents the depth-averaged near-inertial kinect energy of the common water depth from 50 to 250 meters, and the lines with other color are of each observation period. The standard deviation of common water depth from 50 to 250 m is 8.7 J. The observation data of the period from September 2010 to Augast 2011 are abandoned due to deeper observation water depth
表2 观测时间段内冬、夏季台风信息及其对应的近惯性振荡
Table 2 Near-inertial oscillations corresponding to typhoons during the observation period in winter and summer
季节 近惯性振荡发生时间段 是否参与合成
2007年08月21日至2007年09月13日
2008年08月01日至2008年08月21日
2008年09月23日至2008年10月17日 否
2009年07月30日至2009年08月26日
2009年09月25日至2009年10月09日 否
夏季 2010年07月14日至2010年08月05日 否
2010年08月15日至2010年09月04日
2012年07月28日至2012年08月20日 否
2013年06月25日至2013年07月16日 否
2013年08月01日至2013年08月29日
2013年09月25日至2013年10月12日 否
2007年10月15日至2007年10月28日
2007年11月02日至2007年12月01日 否
2008年02月08日至2008年02月27日
2009年03月07日至2009年04月04日
冬季 2010年03月05日至2010年04月13日 否
2011年09月25日至2011年11月16日
2012年10月22日至2012年11月26日 否
2012年12月18日至2013年01月13日
2013年10月12日至2013年10月29日
图3 垂向平均背景环流和近惯性流速分布
左图是夏季时的分布,右图是冬季时的分布;保留1个月以上周期的海流运动作低通滤波,获得背景环流;采用带通滤波器,从流速观测资料中提取近惯性振荡信号,滤波频段设定为0.8~1.2 f;红色线段表示垂向平均背景环流流速分布,红色实线(粗)代表背景环流流速东分量,红色虚线(细)表示背景环流流速北分量;蓝色线段表示近惯性振荡垂向平均流速分布,蓝色实线(粗)表示近惯性振荡流速东分量,蓝色虚线(细)表示近惯性振荡流速北分量
Fig.3 A diagram of depth-averaged background circulation and near-inertial current
The background circulation is obtained by low pass filter, and the near-inertial current is achieved by bandpass filter (0.8~1.2 f) from observation data. The red line represents the depth-averaged background circulation, including east component (coarse) and north component (fine). The blue line represents depth-averaged near-inertial current, including east component (coarse) and north component (fine).The left picture show the season of summer, and the right is winter
图4 不同方向背景流速下的合成能量功率谱及其沿水深变化
(a)速度能量谱随频率变化情况;(b)夏季时速度能量谱随水深和频率的变化规律;(c)冬季时速度能量谱随水深和频率的变化规律
Fig.4 A diagram of synthetic energy spectrum and its variation along water depth in different direction background circulations
(a)Synthetic energy spectrum under background circulations of two directions, the red line represents east component of background circulation, the blue line is the north component, and the black lines represents local inertial frequency, diurnal tide (K1 and O1) and semidiurnal tide (M2 and S2) frequency. Energy spectrum’s variation along water depth in summer and (b) in winter (c)
图5 能量旋转功率谱分布
红色实线表示东北向背景环流下的顺时针旋转功率谱;红色虚线表示东北向背景环流下的逆时针旋转功率谱;蓝色实线表示西南向背景环流下的顺时针旋转功率谱;蓝色虚线表示西南背景环流下的逆时针旋转功率谱
Fig.5 A diagram of energy rotation power spectrum
The red lines represent rotation power spectrum under the northeast background circulation, including the clockwise component (solid line) and counterclockwise component (dotted line). The blue lines represent rotation power spectrum under the southwest background circulation, including the clockwise component (solid line) and counterclockwise component (dotted line)
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