南海北部深层近惯性振荡信号研究

DEEP NEAR-INERTIAL WAVE IN THE NORTHERN SOUTH CHINA SEA

本研究通过分析布放在南海北部的着陆器流速数据,研究一支蓝移的近惯性振荡信号,发现该信号可以传到600m水深以下,持续时间为11月3 16日。该信号的最大的东向流速为0.133m/s,最大南向流为0.124m/s。谱分析发现垂向流速呈现出5个不同的流核,最强流核发生在600 650m位置。近惯性能量下传速度为67±5m/d,从600m下传到1000m的位置能量耗散18%。经验正交函数(empirical orthogonal function,EOF)分解结果显示,这次近惯性振荡信号开始是第一模态占主导,随后变成高阶模态为主导的形式。由于不知道其信号生成的源头,所以无法确定近惯性振荡形成原因,结合前人的研究结果,可以排除台风引起此次近惯性振荡信号的生成。卫星的海表高度异常显示,此时的正涡度有利于此次近惯性振荡发生蓝移特征。

Based on the ADCP data in the lander located in the northern South China Sea(SCS),a blue shift near-inertial wave signal is studied.The lander was deployed in the northern SCS at 22.10°N/119.28°E in 1135m depth working from July 2017 to January 2018.This near-inertial wave signal transmitted to 600m depth during September 3 16.The maximum meridional velocity was 0.133m/s and the maximum zonal velocity was 0.133m/s.Five different energy cores in the near-inertial frequency band were recognized in spectrum analysis.The maximum energy core was in 600 650m depth.The vertical group velocity was 67±5m/d downward.The energy dissipation was 18%from 600 to 1000m.This near-inertial signal began with the first EOF mode dominant,and then became a combination of higher-order EOF mode dominant.Combined with the results of previous studies,we found that the near-inertial oscillation signal was not caused by a typhoon.As the source of the signal generation was unknown,the cause of the near-inertial oscillation could not be determined.The sea level anomaly data by satellite show that the positive vorticity at that time was conducive to the blue shift of the near-inertial waves.