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arXiv 2105.09802math.NAcs.NA
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增量弱约束4D-Var状态列式的时间并行预处理

On time-parallel preconditioning for the state formulation of incremental weak constraint 4D-Var

Ieva Daužickaitė, Amos S. Lawless, Jennifer A. Scott, Peter Jan van Leeuwen

摘要:

使用高度的并行性对于有效地进行数据同化是必不可少的。增量弱约束四维变分同化方法的状态方程允许在时间维上进行并行计算。在这种方法中,解决方案是近似最小化一系列的二次费用函数,使用共轭梯度法。要在实践中使用这种方法,需要有效的预处理策略,保持并行计算的潜力。我们检查近似的控制变量变换(CVT)技术时,后者是有益的。新的策略采用了一个随机的奇异值分解,并保留了潜在的并行在时域。Lorenz 96模型的数值结果表明,这种方法在前几次迭代中加速了最小化,当CVT表现良好时,结果更好。

英文摘要:

Using a high degree of parallelism is essential to perform data assimilation efficiently. The state formulation of the incremental weak constraint four-dimensional variational data assimilation method allows parallel calculations in the time dimension. In this approach, the solution is approximated by minimising a series of quadratic cost functions using the conjugate gradient method. To use this method in practice, effective preconditioning strategies that maintain the potential for parallel calculations are needed. We examine approximations to the control variable transform (CVT) technique when the latter is beneficial. The new strategy employs a randomised singular value decomposition and retains the potential for parallelism in the time domain. Numerical results for the Lorenz 96 model show that this approach accelerates the minimisation in the first few iterations, with better results when CVT performs well.

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