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STUDY ON THE FORMATION PROCESSES OF THE INTERMEDIATE AND BOTTOM MIXED LAYERS NEAR THE CONTINENTAL SHELF BREAK

大陆架断裂附近中底混合层形成过程研究

基本信息

批准号：
05640480
负责人：
MATSUNO Takeshi
金额：
$ 1.28万
依托单位：
NAGASKIi UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05640480/
关键词：
Internal wave Bottom mixed layr Turbulent dissipation rate Vertical mixing 鉛直渦拡散係数

项目摘要

During 5 to 7 August, 1993 and during 4 to 7 August, 1994, temporal variations of current velocity and temperature by mooring arrays just above the sloping bottom with several current meters, temperature distribution with CTD and XBT cast, vertical distribution of the turbulent energy dissipation epsilon with MSP,and in 1994 temporal variation of the fine structure of temperature with thermistor-chain were obtained around the area near the continental shelf break in the East China Sea.Mooring current meters caught short time scale fluctuations which took place intermittently within the bottom mixed layr. These small scale fluctuations may be caused by instability due to shear flow in the stratified fluid, that is KH-instability. We can consider the instability must play an important role to form the bottom mixed layr. Small scale internal waves with frequencies near the Brunt-Vaisala frequency were also generated along with the small scale turbulent fluctuations.However, we could not detect an evidence of breaking of internal waves from the measurement of temporal variations of temperature fine structure near the bottom mixed layr with the thermistor-chain.The maximum value of epsilon obtained by MSP is about 10^<-3>cm^<2s>^<-3>. Time scale of turbulence which is estimated from the value of epsilon is about 3 hours for the turbulent energy of 10 cm^2s^<-2>. This may correspond that the small scale fluctuations measured from mooring system continued for a few hours in a thin layr.

1993年8月5日至7日和1994年8月4日至7日，在东中国海陆架断裂附近海域，用多台测流仪观测了斜底上方系泊阵列测得的流速和温度的时间变化、用CTD和XBT测得的温度分布、用MSP测得的湍流能量耗散量的垂直分布和用热电阻链测得的1994年温度精细结构的时间变化。这些小尺度的波动可能是由层状流体中剪切流动引起的不稳定性引起的，即KH不稳定性。可以认为，失稳对底部混合层的形成起着重要作用。伴随着小尺度湍流起伏，也产生了频率接近Brunt-Vaisala频率的小尺度内波，但通过测量热电阻链混合层底部温度精细结构的时间变化，我们没有发现内波破裂的证据。MSP获得的最大epsilon值约为10^&lt；-3；cm^&lt；2s&gt；-3&lt；-3。对于10 cm~(-2)s~(-2)~(-2)的湍流能量，由epsilon值估算的湍流时间尺度约为3小时。这可能对应于从系泊系统测得的小尺度波动在薄层中持续了几个小时。