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Nonlinear effects in 4D-Var

机译:4d-var中的非线性效应

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摘要

The ability of a data assimilation system to deal effectively with nonlinearities arising from the prognostic model or the relationship between the control variables and the available observations has received a lot of attention in theoretical studies based on very simplified test models. Less work has been done to quantify the importance of nonlinearities in operational, state-of-the-art global data assimilation systems. In this paper we analyse the nonlinear effects present in ECMWF 4D-Var and evaluate the ability of the incremental formulation to solve the nonlinear assimilation problem in a realistic NWP environment. We find that nonlinearities have increased over the years due to a combination of increased model resolution and the ever-growing importance of observations that are nonlinearly related to the state. Incremental 4D-Var is well suited for dealing with these nonlinear effects, but at the cost of increasing the number of outer loop relinearisations. We then discuss strategies for accommodating the increasing number of sequential outer loops in the tight schedules of operational global NWP.
机译:数据同化系统有效处理从预后模型产生的非线性或控制变量与可用观察之间的关系的能力在基于非常简化的测试模型的理论研究中得到了很多关注。已经完成了更少的工作来量化非线性在运营,最先进的全球数据同化系统中的重要性。本文中,我们分析了ECMWF 4D-VAR中存在的非线性效应,并评估增量制剂在逼真的NWP环境中解决非线性同化问题的能力。我们发现,由于模型解决方案的组合以及与国家非线性相关的观察结果的结合,非线性多年来增加了多年。增量4d-var非常适合处理这些非线性效果,但以增加外环的数量的成本增加。然后,我们讨论在运营全球NWP的紧密时间表中容纳越来越多的顺序外环循环的策略。

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  • 来源
    《Nonlinear processes in geophysics》 |2018年第3期|共17页
  • 作者单位

    European Ctr Medium Range Weather Forecasts Shinfield Pk Reading RG2 9AX Berks England;

    European Ctr Medium Range Weather Forecasts Shinfield Pk Reading RG2 9AX Berks England;

    European Ctr Medium Range Weather Forecasts Shinfield Pk Reading RG2 9AX Berks England;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地球物理学;
  • 关键词

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