The design of ocean turbulence measurement with a Moored instrument

The newly designed Instrument MTMI (Moored Turbulence Measuring Instrument) developed by OUC (Ocean University of China) had been deployed in the South China Sea from October 19, 2013 to February 10, 2014 at 21° 09.900' N 117°42.031' E and succeed to collect time series for about 115 days in 250-m-deep water. According to the requirements of turbulence measurement, the mechanical design was developed for turbulence observation platform to achieve stability and good flow tracking. By analyzing the pitch varying with flow speed, the results suggested that the platform satisfies the requirements of stability. Then, the heading of instrument compared with the flow direction measured by RCM (Recording Current Meter), and the two groups of data matched well which showed that our platform has a good ability to track the vibration of the flow direction. Finally, the power spectrum curves of shear signals and the theoretical Nasmyth spectrum also matched well and the rate of turbulence dissipation are 10^-7W kg^-1 approximately. In general, instrument mechanics were rationally designed and MTMI provided a good observation platform for the long-term turbulence measurements.

I. Introduction

The ocean turbulence plays an important role in cognizing the process of ocean circulation and significantly improving climate modeling. It also has a significant impact on the study of marine ecological environment and the distribution of suspended materials [1]. The ocean turbulence has grown up to be an important subject in the marine science research. Conventionally, the measurements of turbulence and mixing are usually limited to surveys of short time’ duration and the samples are incomplete and sporadic [2]. Therefore, turbulence measurements for long-term periods are needed to improve our understanding of the ocean mixing process on ocean circulation dynamics. So the technologies for long-term measurements are becoming increasingly important.