太湖水温空间差异驱动机制和水温三维模型研究

Forecasting of water temperature is an important part of algal bloomimg warning.Because water temperature is the most important physical factor determining the growth of algae and aquatic plants and affecting algal bloomimg and water quality in eutrophic lakes. There are spatial and vertical difference in ecosystem structure and physical-chemical elements in the large shallow Lake Taihu.Thus,based on previous research achievements in water-air interface heat exchange and attenuation of solar radiation, field observaions and laboratory simulations about the water-sediment interface heat flux and the intensity of heat exchange in different types of water-sediment interface are carried out. In view of research results, the express of Source and sink terms and boundary conditions will be found and 3-D temperature simulation model in Lake Taihu can be built and then tested on measured data from different regimen.In addition, we shall reveal the mechanism of water temperature spatial difference in Taihu Lake with numerical simulation experiments under different scenarios (with and without aquatic plants and algae, different water flow, temperature, solar radiation, as well as the water-sediment interface heat flux, etc.).Forecast of water temperature can provide a temperature variable for long-term diagnosis and prediction of algal bloomimg to improve the accuracy of prediction and reduce the harm of algal blooms in Lake Taihu.

水温是决定藻类和水生植物生长的最为重要物理因素，对富营养化湖泊藻类水华暴发和水质具有重要影响，进行水温预测计算是藻类水华预警预测重要内容。本申请针对大型浅水湖泊太湖，生态系统结构以及物理化学要素存在显著的水平和垂直方向差异特征，拟在国内外水-气界面热交换、太阳辐射在水体衰减等方面的研究成果基础上，重点进行不同类型湖区和底质条件下的水-沉积物界面热通量以及水体热源汇强度变化的观测与室内模拟试验，研究水-沉积物热通量、水体热源汇的参数化表达式，构建太湖三维水温模型；通过不同水情年水温模拟，进行模型校验和验证；开展不同情景（含与不含水生植物和藻类、不同出入湖流量和水温、不同的太阳辐射空间分布，以及不同的水-沉积物界面热通量等）的数值试验，通过结果对比分析，揭示太湖水温空间差异的驱动机制，提供太湖藻类水华长期诊断与预测预警所需温度输入过程，为提高藻类水华预警预报的精度和减轻太湖藻类水华危害服务。

针对太湖作为浅水湖泊易受沉积物影响这一特点，开展了水-沉积物界面热通量测量装置设计和测量方法研究，进行水体热量收支与温度变化模型的调研；通过2013年到2015年两年多时间太湖多点位长时间序列的温度链数据观测，弄清了太湖不同层次水温的时空差异和变化特征，首次获取了太湖不同水域沉积物温度周年变化特征和太湖不同水层及沉积物昼夜均温差异特征，发现大部分日期太湖水-沉积物界面夜晚均温大于白天均温；揭示了不同深度层温度之间的关系，建立了计算水沉积物界面的温度计算经验公式；并结合不同湖区温度的连续对照观测，阐明了水生植被对水温变化的重要热缓冲作用；本研究获得了太湖不同区域水土界面两侧沉积物温度梯度，弄清了太湖不同区域沉积物热源汇差异和水-沉积物传热方向的变化特征，计算了近底层水温垂向扩散系数；结合太湖特点，构建了太湖温度变化动力学概念模型和数学模型，给出了模型数值解法，并进行了模型计算程序的开发，利用观测获得的参数及水温数据进行了三维水温模型的参数率定和模型验证。