夏季长江冲淡水两种扩展形态的机理分析

The Changjiang diluted water (CDW) has two basic forms appeared as band and patch in its summertime extension, which was frequently observed by field survey and remote sensing methods. Some dynamic factors, like tide, wind-induced current, Taiwan warm current and frontal baroclinically unstable, are driving forces in the two extension processes by current studies. However, the relative importance of how these factors effecting on the two CDW forms are barely analized. Targeting to the crucial roles of the above dynamic factors on the two CDW forms in summertime extension, the main research contents are the following: explore evolution characters of the two CDW forms from newest remote sensing data; reproduce extention processes of the two CDW forms with high resolustion model; quantify relative importance of the dynamic factors by a series of numerically sensitive tests. The detailed dynamic factors include relative contributions among tidal current, wind-induced current and Taiwan warm current on forming the CDW banding pattern, relative contributions between tidal mixing and wind mixing on shaping the CDW patches, and Taiwan warm current effecting on fomation and evolution of the two CDW patterns. The research results will help us better understand the processes and mechanism of the CDW extention in summer through dynamic analysis.

现场和遥感观测都显示夏季长江冲淡水（CDW，Changjiang Diluted Water）以带状和斑块状两种基本形态向外海扩展。前人的研究表明，潮流、风海流、台湾暖流及锋面的不稳定性等在产生这两种扩展过程中起着一定作用，但对这些动力因子在影响CDW扩展形态中的相对重要性缺乏综合分析。项目以揭示各种动力因子在夏季CDW扩展形态中扮演角色为目标，从最新观测资料中提取CDW扩展过程的演变特征，用高分辨率数值模型再现CDW扩展过程，利用一系列的敏感性数值试验量化各种动力因素贡献，如潮流、风海流和台湾暖流在形成CDW带状形态中的相对贡献，潮混合和风混合在形成CDW斑块形态中的相对贡献，台湾暖流在CDW两种扩展形态的形成和演变中的贡献。研究结果将有助于我们从动力学角度更好地认识夏季CDW扩展过程和机理。

本项目研究长江冲淡水带状和斑块状两种扩展形态，以及风、潮流和台湾暖流在夏季扩展中的作用。研究结果显示，风和潮流共同作用是控制长江冲淡水带状和斑块状扩展的主要原因；潮流还影响长江冲淡水在长江浅滩上的长期东北向扩展；台湾暖流影响低盐水团在夏季向外海的长期输送，以及冬季跨东海南部陆架的短期输送过程。基于以上研究内容，发表了5篇SCI/EI论文，包括JGR、JMS和OS等国际期刊。项目研究成果从机理上深入认识了长江冲淡水的物质输送过程，研究成果将进一步应用于我国重点养殖区生态动力过程分析，为我国科学水产养殖提供水动力方面的技术支持。