基于台风过程的三维环流结构及水环境影响机制研究

The change of the three-dimensional circulation structure，it's effects and driving mechanics based on Typhone Process are studied in view of the folling existed problems,e.g. the inaccuracy of Eularian residual current and the limination to the widely application of parallel mode based on MPI, especially the lack of research on the Short Term Circulation(STC) such as the effects of strong meteorlogic process on the circulation pattern and the time-delayed responses of the ocean. Firstly, a tide-storm surge-Typhoon wave two-way coupling model is developed based on GPU parallel algorithms for coastal and offshore ocean of China. Secondly, the time-dependent response of STC in studied ocean under Typhoon process are stuided thoroughly, including the spatial scale and the minimum identificaion scale of the three-dimensional STC structure, the effects of intensity of the Typhoon on the vertical velocity and vertical circualtion structure, the realtionship between the vertical strcuture and horizontal structure. At the same time, a comprehensive numerical method based on the joint description of Lagrangian residual current, Lagrangian particle tracing and the Lagrangian coherent structure. Based on all the above research, the characteristics of spatial and temporal distribution of the mixing structure and thickness of mixing layer from numerical simulation, the Sea Surface Temperature（SST）from analysis of satelite data，the suspended matter and chlorophyll from satelite data are analyzed in detail, which can supply a conceivable validation of the circulation model besides their functions as the description of effects of Typhoon on ocean Hydrodynamic, water quality and ecosystem. At last, the effects of the STC on monthly and seasonal circulation for strong Typhoon and two Typhoons happened with short time interval are studied further. Hopefully, the driving mechanics of the effects of the change of STC under Typhoon process on coastal and offshore ocean are obtained. The two-way coupling mode based on GPU parellel algorithm and the comperehensive Lagrangian method for circualtion can lay a good foundation for further research on the effects of Typhoon on sediment transport, water quality and ecosytem.

本课题针对国内外近浅海环流研究中存在的不足，特别是缺乏对短期环流、强能天气过程对环流结构的影响及滞后水环境效应研究，以我国近浅海为研究区域，建立基于GPU并行算法的潮流-风暴潮-台风浪联合作用下的双向耦合环流模式。重点进行近浅海环流结构对典型台风过程的反应时效，三维短期环流尺度及最小识别尺度；台风强度对近浅海的垂向速度和垂向环流结构的影响；小尺度垂向环流和水平环流的相互关系的研究。同时进行短期环流计算方法的改进和探讨，发展结合拉格朗日余流、粒子追踪法和相干结构的拉格朗日综合环流描述方法。通过对近浅海混合特征、水文特征、物质输运特性的时空变化以及短期环流结构的变化对长期环流结构的影响研究等，得出环流结构突变后的水环境影响机制。通过课题中台风过程对近浅海环流动力学影响机制的研究、建立的耦合模式及拉格朗日综合环流描述方法可为进一步开展台风对泥沙输运、水质和生态环境的影响奠定基础。

全球极端天气不断增多，课题针对国内外缺乏对短期环流、强能天气过程对环流结构的影响及滞后水环境效应的研究，开展了基于台风过程的三维环流结构及水环境影响机制研究。.1)建立了基于GPU高效并行、高精度、具有良好质量守恒特性且能较充分考虑台风对潮流和波浪作用的耦合近浅海环流模式。基于GPU并行算法的模型相对于单线程串行计算模式计算效率提高达25-30倍；发展了一系列的边界处理方法，提高了模型解决浅水问题的适用性及稳定性。基于线性聚焦破碎波引起的波谱能量在频率间的耗散和转移规律，尝试性改进了海浪模型中白浪耗散项，台风浪成长过程的模拟精度有所提高。.2)通过引入基于有限时间李雅普诺夫指数（FTLE）的拉格朗日相干结构（LCS）时变系统分析方法，结合余流和概要图，发展了描述海域物质输运特征和短期环流结构的拉格朗日综合方法。该方法可以分别从物质输移路径、水体输运时间尺度和不同运动特性水团的分区多方面揭示海湾物质输运的时空演化特征，有助于了解物质输运和分布的深层原因。.3)利用改进的波流耦合模型，分别以狭长海湾和南海为例，得到了典型台风过程对海域三维环流结构影响的尺度和时效及其动力学机制。近浅海分别从拉格朗日余流、粒子运移距离及路径、拉格朗日相干结构、滞留时间分析了台风的影响；开阔海域中研究了典型台风过程对南海海域局部水流结构、温盐结构和海洋内部混合特征的影响，得到台风对开阔海洋水体影响的水平尺度、垂向尺度和时间尺度。研究结果有助于深刻认识台风过程对海洋水体混合和水环境的影响。 .4)通过卫星遥感技术手段，建立了特定海域的海洋水色要素反演模型；通过对比悬浮物浓度、叶绿素a浓度、海表温度SST在台风过程前后的时空变化，得到了台风发生前后水环境各要素时空变化特征。.以上的研究分别在环流模型和波浪模型改进、物质输运特性描述方法和多角度水环境变化的预测几个方面取得了实质性的进展。得到了有关台风过程对海洋水体混合和水环境影响的重要结论。