基于水动力箱式模型的长江口及邻近水域物质通量研究

发布时间：2018-06-07 08:52

本文选题：长江口 + 水动力箱式模型　；参考：《中国科学院研究生院（海洋研究所）》2014年博士论文

【摘要】：长江口及邻近水域（30.5°N-32°N,122°E-123°30′E）是我国近海富营养化的典型水域，其物质通量研究具有重要意义。传统的“水-盐-营养盐”箱式模型是海岸带陆海相互作用研究计划（LOICZ）研究河口与近岸物质通量的一种稳态模式。该模式没有充分考虑研究区域的水动力因素，模式结果受箱体划分影响很大，只能估算盐度差异明显的界面之间的物质通量，对与海岸线平行以及流系复杂多变水域的物质通量估算无能为力。针对长江口及邻近水域流系复杂多变的特点，本研究尝试对传统箱式模型进行改进。本研究将物质输运过程正交分解为水平方向的物质输运和垂直方向的物质输运，水平与垂直方向的物质输运分别分为对流引起的物质输运和扩散引起的物质输运。以区域海洋模式系统（ROMS）为基础，通过Matlab编程，，将水动力模型的流场数据准确匹配到箱式模型的箱体边界上，实现了水动力模型与箱式模型的联接，成功构建了基于水动力模型的改进的箱式模型（本研究简称为“水动力箱式模型”）。运用构建的水动力箱式模型，计算并阐释了研究区域的水平水通量、垂向水通量和边界水通量的空间分布与季节变化，探讨分析了研究区域水通量的动力因素与机制，以及研究区域水体交换与缺氧之间的关系，为该水域物质通量研究提供了准确的水量基础。在此基础上，利用2005年2月、5月、8月、11月4个航次的监测数据，计算并阐释了研究区域营养盐的水平通量、垂向通量和边界通量及其营养盐结构的空间分布与季节变化，探讨分析了研究区域营养盐通量的动力因素与机制。研究表明，表层水体水平水通量的季节排序为冬季秋季夏季春季；底层水体水平水通量的季节排序为夏季春季冬季秋季；秋、冬季底层水通量约比表层小1个数量级，夏季底层水通量约为表层的1/2，春季表、底层水通量差别最小。研究区域水通量整体受季风控制，季风使水体在南-北方向上季节性交替输运，台湾暖流对春、夏季底层水体向北输运具有重要作用，CDW、地形、向岸风等多种因素对水通量的时空分布态势具有重要作用。夏季上升流水通量为18.53m3/s，春季为12.55m3/s，冬季为13.07m3/s，秋季为14.25m3/s。西边界水通量方向全年向海。南、北边界的表层水通量与季风方向总体一致。东边界水通量方向规律不明显。南、北边界的水通量约大于西边界一个数量级。东边界水通量，除春、秋季以外，明显小于西边界。秋、冬季南、北边界的表层水通量约比底层水通量大1个数量级，春季约为底层水通量的1/2，夏季约为底层水通量的两倍。经东边界直接进入123.5°E以东外海水域的水通量极少（夏季5.41m3/s），且明显小于春、秋季经东边界自东部外海流入的水通量（12.45m3/s、27.75m3/s）。全年计算，约187.73m3/s的水通量自南边界流出研究区域，后经海洋环流系统间接入海。研究区域水体交换主要依赖季风方向、同层水体之间的的水平水通量。该水域底层水体缺氧的本质原因是跃层阻隔了表、底层水体之间的氧气交换。表层水体水平营养盐通量的季节排序为冬季秋季夏季春季；底层水体水平营养盐通量的季节排序为夏季春季冬季秋季；表层水体水平营养盐通量的空间差异与季节变化均显著大于底层水体。研究区域营养盐通量主要受物理作用控制，以生化作用为辅。与水通量相似，季风使营养盐在南-北方向上季节性交替输运，台湾暖流对春、夏季底层营养盐向北输运具有重要作用，是春、夏季长江径流影响范围向东扩展的重要限制因子，此外，垂向营养盐通量补给、外海水团入侵和初级生产消耗等多种因素对营养盐通量的时空分布态势具有重要作用。垂向DIP通量是DIP的重要来源。垂向营养盐通量的总体特征主要是由上升流通量的时空分布决定的。同一季节的上升流营养盐通量显著大于向上扩散的营养盐通量，且上升流营养盐通量与向上扩散的营养盐通量的产生区域基本重合。春、夏季的上升流营养盐通量和向上扩散的营养盐通量均显著大于秋、冬季。DIP上升流通量(5.83mol/s)和向上扩散通量(5.55mol/s)最大值均发生在夏季，但春季垂向通量对其影响最大。春季DIN、DSI垂向通量分别比水平通量少3-7倍、3-5倍，DIP垂向通量与水平通量接近相等；夏季DIN、DSI、DIP垂向通量分别比水平通量少3-6倍、5-10倍和5-8倍；秋、冬季，三种营养盐垂向通量均比水平通量小2个数量级。研究发现，同一季节流经南、北边界的营养盐通量均显著大于流经东、西边界的营养盐通量。四个边界中，经东边界与东部外海水体交换的营养盐通量最小，比经西边界流入的营养盐通量小大约1-2个数量级。西边界营养盐通量方向终年向海，南、北边界营养盐通量方向与季风方向基本一致，秋、冬季南向，春、夏季北向。但秋季为季风转换期，北边界表、底层营养盐通量方向相反，表层南向，底层北向。东边界营养盐通量方向规律不明显。研究区域扮演着营养盐从黄海向东海输送的“中转站”角色。来自西边界的营养盐通量主要被局限在122.5°E以西的近岸区域，被直接输送到123.5°E以东外海的极少。全年计算，约7149.82mol/s DIN，4097.97mol/s DSI,115.42mol/s DIP自南边界流出研究区域。相比传统箱式模型，水动力箱式模型弥补了传统箱式模型未能充分考虑水动力因素的缺陷，对复杂水动力环境下的营养盐通量估算具有明显优势，为河口物质通量研究提供方法借鉴。
[Abstract]:The model of " water - salt - nutrient " box model is a steady state model for studying the flux of river mouth and coastal matter . The traditional " water - salt - nutrient salt " box model is a steady state model for studying the flux of river mouth and coastal matter .

Based on the regional ocean model system ( ROMS ) , the flow field data of the hydrodynamic model is accurately matched to the box boundary of the box model , and an improved box model based on the hydrodynamic model is successfully constructed ( this study is simply referred to as " hydrodynamic box model " ) .

This paper calculates and explains the spatial distribution and seasonal variation of the water flux , vertical water flux and boundary water flux in the study area by using the constructed hydrodynamic box model , and studies the dynamic factors and mechanism of the regional water flux , and studies the relationship between water exchange and anoxia in the area . Based on this , the paper calculates and explains the spatial distribution and seasonal variation of the nutrient salt in the study area , and discusses the dynamic factors and mechanism of the nutrient salt flux in the study area .

The results show that the seasonal ranking of the horizontal water flux in the surface water is the spring of autumn in winter in winter ;
The seasonal ranking of the level water flux in the bottom water body is autumn in spring in summer ;
In autumn , the water flux in the north boundary is about 1 / 2 of the surface layer , the spring is 12.55m3 / s , the winter is 13.07m3 / s , the spring is 12.55m3 / s , the spring is 13.07m3 / s and the autumn is 14.25m3 / s . For the whole year , the water flux of about 187.73m3 / s flows out of the study area from the south boundary , and then is directly entered into the sea through the ocean circulation system . The research area water body exchange mainly depends on the monsoon direction and the horizontal water flux between the same layer water body . The essential reason of the anoxic of the bottom water body of the water body is that the jump layer blocks the oxygen exchange between the table and the bottom water body .

The seasonal ranking of the level nutrient flux in the surface water body is winter autumn summer spring ;
Seasonal ordering of the level nutrient flux in the bottom water body is autumn in spring in summer ;
The seasonal variation of nutrient salt flux in the surface water body is significantly greater than that of the underlying water body . The research area nutrient flux is mainly controlled by the physical action , and the seasonal alternation of nutrient salt in the South - North direction is important to the north transport .

Vertical DIP flux is an important source of DIP . The overall characteristic of vertical nutrient flux is determined by the space - time distribution of upwelling flux . The flux of upwelling nutrient salt in the same season is significantly greater than that of the upward diffusion . In spring and summer , the flux of nutrient salt and the flux of upward diffusion are significantly higher than those in autumn and winter . In spring , the vertical flux of DIP is 3 - 7 times less than the horizontal flux , 3 - 5 times higher than that of the horizontal flux , and the vertical flux of DIP is nearly equal to the horizontal flux .
in summer , that vertical flux of din , dsi and dip is 3 - 6 times , 5 - 10 times and 5 - 8 times less than the horizontal flux , respectively ;
In autumn and winter , the vertical flux of three nutrient salts is 2 orders of magnitude smaller than that of the horizontal flux .

The study shows that the fluxes of nutrient salts flowing through the south and north boundary in the same season are significantly larger than those flowing through the eastern and western boundaries . The fluxes of nutrient salts in the eastern boundary and the East China Sea are the smallest , which is about 1 - 2 orders of magnitude smaller than that of the western boundary . However , the nutrient salt flux from the west boundary is mainly confined to the coastal areas in the east China Sea . The study area is mainly confined to the outer sea of 123.5 掳 E . The study area is calculated at about 7149.82mol / s DIN , 4097.97mol / s dsi and 1150.42mol / s DIP from the south boundary .

Compared with the traditional box model , the water dynamic box model makes up the failure of the traditional box model to fully consider the water power factor , and has obvious advantages to the estimation of the nutrient salt flux under the complex hydrodynamic environment , and provides a method for the research of the estuary material flux .
【学位授予单位】：中国科学院研究生院（海洋研究所）
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV14;X143

【参考文献】