| LIANG Hui,ZHAO Wei,DAI Dejun,ZHANG Jun. 2014. Estimation of vertical diffusion coefficient based on a onedimensional temperature diffusion equation with an inverse method. Acta Oceanologica Sinica, 33(5):28－36 |
| Estimation of vertical diffusion coefficient based on a onedimensional temperature diffusion equation with an inverse method |
| 基于一维扩散方程反演温度垂直扩散系数的变分方法 |
| Received:April 17, 2012 Revised:July 08, 2013 |
| DOI：10.1007/s13131-014-0472-z |
| Key words:inverse method temperature diffusivity one-dimensional vertical diffusion equation |
| 中文关键词: 反演算法, 温度扩散系数, 一维垂向扩散方程 |
| 基金项目:The Program for New Century Excellent Talents in University of the Ministry of Education under contract No. NCET-10-0764; the National High Technology Research and Development Program of China (863 Program) under contract No. 2013AA09A502; the National Natural Science Foundation of China under contract Nos 40876015 and 41176010. |
| Author Name | Affiliation | E-mail | | LIANG Hui | Physical Oceanography Laboratory, Ocean University of China, Qingdao 266100, China | | | ZHAO Wei | Physical Oceanography Laboratory, Ocean University of China, Qingdao 266100, China | | | DAI Dejun | The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China
Key Laboratory of Marine Science and Numerical Modeling, State Oceanic Administration, Qingdao 266061, China | djdai@fio.org.cn | | ZHANG Jun | The Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, China | |
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| Abstract: |
| Diapycnal mixing is important in oceanic circulation. An inverse method in which a semi-explicit scheme is applied to discretize the one-dimensional temperature diffusion equation is established to estimate the vertical temperature diffusion coefficient based on the observed temperature profiles. The sensitivity of the inverse model in the idealized and actual conditions is tested in detail. It can be found that this inverse model has high feasibility under multiple situations ensuring the stability of the inverse model, and can be considered as an efficient way to estimate the temperature diffusion coefficient in the weak current regions of the ocean. Here, the hydrographic profiles from Argo floats are used to estimate the temporal and spatial distribution of the vertical mixing in the north central Pacific based on this inverse method. It is further found that the vertical mixing in the upper ocean displays a distinct seasonal variation with the amplitude decreasing with depth, and the vertical mixing over rough topography is stronger than that over smooth topography. It is suggested that the high-resolution profiles from Argo floats and a more reasonable design of the inverse scheme will serve to understand mixing processes. |
| 中文摘要: |
| 由于在大洋环流中的重要作用，海洋混合逐渐成为物理海洋学研究的热点之一。现场观测是认知海洋混合时空分布特征最有效的手段，然而目前针对湍动能耗散率的观测数据还很少，在该情况下，利用常规温盐资料反演垂向扩散系数不失为一个了解垂向混合的有效途径。本文基于垂向一维扩散方程，建立了反演垂向扩散系数的变分方法。这里我们采用半隐半显格式进行数值差分。为了检验该方法的可行性和对初始温度场、扩散系数初猜值、垂向分辨率等的敏感性，我们开展了理想实验。检验结果表明，本文中我们建立的反演模型对实际海洋数据中存在的观测误差以及扩散系数的初始猜值不敏感，在各种情况下都具有较高的可行性，是一种估算实际海洋中温度扩散系数的有效方法。随后，我们将此法用于Argo数据，以分析北太平洋中部垂向混合的时空分布特征。结果表明大洋上层的垂向混合表现出明显的季节变化且变化幅度随深度减弱；地形的粗糙度对大洋垂向混合有重要影响，粗糙区的垂向混合要强于平滑区的。但该方法基于一维温度扩散方程，仅适用于海流较弱的区域。因此对高质量、高分辨率数据的分析以及对反演算法的改进将加深我们对海洋混合过程的理解，是未来工作的方向。 |
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