双LADCP深水大洋测量及资料后处理技术研究

LADCP is the main measurement method for ocean survey. How to extract the reliable and accurate absolute velocity from it is still an international problem to be solved. LADCP observation in deep-water oceans has some restrictive conditions, especially in the depth more than 1000m, such as the “fracturing” of velocity profile data for the lack of particulate matter profile data of velocity, difficulty acquisition of bottom tracking, and high requirements on transducer characteristics. Based on the status quo, we will do exploratory research in two aspects: first, we use the dual LADCP of same frequency, one up and one down, do synchronous observation, to increase the observation samples and suppress the influence of measurement deviation caused by the instrument movement. Besides, we construct a set of on-site observation technology systems including CTD and GPS synchronous observation, control technical points and form technical processes and technical specifications. Second, we establish data post-processing methods for dual LADCP. Based on the core technology that the difference between the velocities of the adjacent two layers in the Ping section is equal to the true flow velocity, we get synchronous control of each element, the flow velocity error control caused by instrument motion, and the overall error control. The verification of the small flow layer are performed according to the Bernoulli equation and dynamic calculation, and the processing result is verified systematic. This study is expected to form a set of reliability plans for observations of full-section currents in the deep ocean region.

LADCP作为海洋大面调查主要的测流方式，如何从其提取可靠、准确的绝对流速，目前仍是一个待解决的国际性问题。LADCP观测在深水大洋，特别是1000m以深存在由于颗粒物少造成的流速剖面数据“断裂”、底跟踪困难、对换能器特性要求高等制约条件。基于现状，本研究从两方面开展探索性研究：一是采用同频率、一上一下、双LADCP同步观测，以增加观测样本量、抑制由于仪器运动带来的流速测量偏差影响，并构建包含CTD、GPS同步观测等一整套现场观测技术体系，把控技术要点，形成技术流程和技术规范；二是建立双LADCP的数据后处理方法。基于同Ping剖面内相邻两层流速的差等于真实流速之差这一核心技术，进行各要素同步性控制、仪器运动导致的流速误差控制、整体性的误差控制。根据伯努利方程与动力计算来进行小流速层的确认和验证，并且对处理结果进行系统性验证。本研究有望形成一套深水大洋区海流全剖面观测的可靠性方案。

本项目致力于自主专研双LADCP的观测技术和资料处理技术，研究内容为：1、对双LADCP深水大洋测量技术和CTD深水大洋测量技术进行了比较全面、深入的研究，构建了包含CTD、GPS同步观测等一整套现场观测技术体系，把控现场观测的技术要点，形成了完整的技术流程。2、为提高SBE9plus CTD的处理精度，提出了一种基于趋势项距平值迭进式方差控制的奇异值剔除方法。3、为解决LADCP底跟踪数据缺失的情况，基于WM15模式测量原理，对靠近底层的水流速度进行处理，实现了底跟踪速度的再提取。4、对LADCP资料处理的算法设计和算法比较分析研究，通过海上实验获取LADCP测量数据的质量控制参数，为进一步的误差分析提供依据。提出并应用“小流速层”和“分段积分”的方式，突破了深海大洋观测的资料处理困局，有效避免了垂向积分造成的误差积累问题。利用MATLAB语言，编制包括算法设计和质量控制等处理过程的系统程序，实现LADCP的资料后处理。5、对东印度洋南部水体夏季航次获取的双LADCP观测数据进行了处理、分析。该项目的研究内容对推动双机同步LADCP观测在深远海调查中的应用及推进我国的海洋学研究具有十分重要的意义。