The University of Reading A Comparison of Potential Vorticity-Based and Vorticity-Based Control Variables
The University of Reading A Comparison of Potential Vorticity-Based and Vorticity-Based Control Variables
复制标题
雷丁大学基于位涡和基于涡度控制变量的比较
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
R. Bannister
中科院分区：
文献类型：
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作者：
D. Katz;A. Lawless;N. Nichols;M. Cullen;R. Bannister
在大多数业务天气预报中心，变分数据同化是使用与实际模式变量不同的一组变量进行的。变量的变换通过假设变换后的变量中的误差是不相关的来简化问题。这一假设的有效性是数据同化准确性的关键。最近提出了一套基于位涡（PV）的变量。这些新的变量被认为更准确地利用了大气的重要动力学特性。在这里，我们提出了新的结果，获得了一个简化的1-D浅水模型，比较PV为基础的变量，目前使用的基于涡量的变量在业务天气预报中心，包括气象局。在各种动态制度的基本假设，即在转换变量的误差是不相关的有效性进行了测试。结果表明，在PV为基础的变量的错误是不相关的所有制度测试。然而，对于基于涡度的变量，情况并非如此。这表明基于PV的控制变量比当前基于涡度的变量更好地表示背景误差。
In most operational weather forecasting centres variational data assimilation is performed using a different set of variables from the actual model variables. The transformation of variables simplifies the problem by assuming that the errors in the transformed variables are uncorrelated. The validity of this hypothesis is key to the accuracy of the data assimilation. Recently a potential vorticity (PV) based set of variables has been proposed. These new variables are thought to exploit more accurately important dynamical properties of the atmosphere. Here we present new results, obtained with a simplified 1-D shallow water model, comparing the PV-based variables to the vorticity-based variables currently used at operational weather forecasting centres, including the Met Office. The validity of the fundamental assumption that the errors in the transformed variables are uncorrelated is tested in a variety of dynamical regimes. The results show that the errors in the PV-based variables are uncorrelated across all regimes tested. This is not the case, however, for the vorticitybased variables. This suggests that the PV-based control variables imply a better representation of the background errors than the current vorticity-based variables.