LADCP观测和资料后处理的关键技术

Key Technology of LADCP Observation and Data Post-Processing

针对 L ADCP这一崭新而又特殊的海流观测技术 ,系统地介绍了 L ADCP/CTD捆绑式测量、罗盘标定、测量设置和附加信息获取等 L ADCP观测中的主要技术问题。在对 L ADCP瓦迭式资料特点进行研究的基础上 ,阐释了 L ADCP资料后处理的关键技术 :首先进行 L ADCP资料初处理和声速剖面校正 ,利用同 ping剖面内相邻两水层的 L ADCP测量值之差等于两水层的真实速度之差这一特性 ,把 L ADCP的所有测量值转化为垂向切变流速 ,求出水柱内各水层的垂向切变率 ,对其按照一定的积分顺序进行深度积分 ,得到水柱内各水层相对于参考层的相对速度 ,利用底跟踪信息可以较直接地求出参考层的速度 ,也可以根据测量过程中 L ADCP和测船相对位置在入水时和出水时保持不变这一基本成立的假定通过 GPS信息求出参考层的速度 ,从而得到整个水柱内各水层的绝对流速。为了提高处理结果的准确度 。

In this paper a new and special current observation technology with LADCP is studied. Some main processes of LADCP observation are introduced including LADCP/CTD binding measurement, compass calibration, measure setup, obtaining additional information, etc. Based on the study of the character of LADCP data, which is described as alternating tiles, the key parts of post-processing are explained. At first, the data should be preprocessed and the sound speed profiles should be corrected. Secondly, measured values could be translated into shear values according to the character that the difference of the measured values between two adjacent layers in the same ping is equal to the one between the absolute velocities in two layers. Thirdly, all the shear values should be integrated by depth in a certain order to get relative velocities. Fourthly, the reference velocities could be calculated directly from bottom tracking information, or indirectly from GPS information provided the relative positions between the LADCP and the vessel are nearly the same at the moments the instrument is launched into and come out of water. At last, the absolute velocities of the whole profile could be calculated from the relative velocities and reference ones. Especially, the data quality control must be applied at every step for improving result.