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杭州湾三维悬浮泥沙输运模型初始场的伴随法反演研究
杜云飞1, 张继才1, 王道胜2
1.浙江大学 海洋学院;2.中国地质大学武汉 海洋学院
摘要:
在悬沙输运的数值模拟中,初始场的准确给定至关重要,当前诸多确定初始场的方案均存在一定的缺陷,因而初始场的准确性有待进一步提高。本文基于一个三维悬沙输运伴随同化模型,通过孪生实验和实际实验,对模型初始场进行了伴随法反演研究。孪生实验中,首先验证了初始场的相对重要性;其次,探讨了初始场的反演结果对优化算法、初始猜测值、卫星遥感数据数量、同化时间窗口宽度和背景流场误差的敏感性;最后,比较了伴随法和插值法重构初始场的能力。孪生实验结果表明:最速下降法对初始场的的优化反演效果要优于三种共轭梯度法和有限记忆BFGS法;初始场的反演效果对初始猜测值、卫星遥感数据数量和背景流场误差不敏感,而对同化窗口宽度较为敏感;与插值法相比,伴随法是重构模型初始场更有效的手段。实际实验中,在杭州湾海域同化典型的小潮时期和大潮时期的GOCI卫星遥感资料所得表层悬沙浓度数据,优化反演了初始场。实际实验结果表明:数据同化后,得到了更符合实际的最优初始场,表明伴随法是实现初始场优化反演的有效手段。该研究对进一步改进悬沙输运模型的初始化方案具有一定的参考价值,也对其它数值模型的初始化方案具有一定的借鉴价值。
关键词:  伴随同化  悬沙输运模型  初始场  GOCI
DOI:10.11693/hyhz20191000189
分类号:
基金项目:国家自然科学基金项目(面上项目,重点项目,重大项目)
INVERSION OF INITIAL CONDITION OF A THREE-DIMENSIONAL SUSPENDED SEDIMENT TRANSPORT MODEL IN HANGZHOU BAY WITH AN ADJOINT METHOD
DU Yun-Fei1, ZHANG Ji-Cai1, WANG Dao-Sheng2
1.Ocean college, Zhejiang University;2.College of Marine Science and Technology,China University of Geosciences
Abstract:
In the numerical simulation of suspended sediment transport, the accurate setting of initial condition is very important. Many schemes to determine initial condition have some defects, so the accuracy of initial condition needs to be further improved.Based on a three-dimensional suspended sediment transport model with the adjoint data assimilation, we used adjoint method to optimize initial condition of the model by running twin experiments and practical experiments. In the twin experiments, the influence of errors of initial condition on the simulation results is first studied. Secondly, the sensitivity of inversion results of initial condition to different influencing factors such as optimization algorithms, initial guess values, number of satellite remote sensing data, widths of assimilation time window and errors of background flow field are discussed; finally, the ability to reconstruct initial condition with adjoint method and interpolation method is compared. The results of the twin experiments show: Steepest descent algorithm is better than three conjugate gradient algorithms and limited-memory Broyden-Fletcher-Goldfarb-Shanno algorithm in optimizing initial condition; the inversion results are less sensitive to initial guess values, number of satellite remote sensing data, and errors of background flow field, but is sensitive to the width of assimilation window; 5. Compared with interpolation methods, adjoint method is a more effective means of reconstructing initial condition of the model. In the practical experiments, the surface suspended sediment concentration data obtained from the GOCI satellite remote sensing data in typical neap and spring tide periods in Hangzhou Bay is used to optimize initial condition. Practical experimental results show: After data assimilation, a more realistic optimal initial condition is obtained, indicating adjoint method is an effective means to optimize initial condition. This research has certain reference value for further improving initialization schemes of suspended sediment transport model, and it also has certain reference value for initialization schemes of other numerical models.
Key words:  adjoint assimilation  suspended sediment transport model  initial condition  GOCI
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