Errors of Interannual Variability and Trend in Dynamical Downscaling of Reanalysis
Errors of Interannual Variability and Trend in Dynamical Downscaling of Reanalysis
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DOI：
10.1029/2009jd013511
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发表时间：
2010-09
影响因子：
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通讯作者：
M. Kanamitsu;K. Yoshimura;Yoo-Bin Yhang;Song‐You Hong
中科院分区：
文献类型：
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作者：
M. Kanamitsu;K. Yoshimura;Yoo-Bin Yhang;Song‐You Hong
[1] 本文研究了动态降尺度分析的年际变化及其相对于全球粗分辨率分析的误差。研究表明，区域模型误差会严重影响季节平均值的年际变化。该误差占据了年际变化的重要部分，特别是在夏季。因此，该地区500 hPa高度的经验正交函数（EOF）主导模态与全球分析存在较大差异。本文对光谱微移的一种变体——尺度选择性偏差校正（SSBC）方法进行了改进，以进一步减少观测误差内的误差。应用该方法进行动力降尺度，减少了分析场（即高度、温度和风）年际变化的误差，使500 hPa高度季节平均EOF与全球分析结果吻合较好。 SSBC 的应用对模型导出的场（例如降水和近地表气温）影响不大。这些领域的改进不如分析领域那么显着，但模拟技能的提高是显而易见的。讨论了年际变化误差的可能原因。没有发现高频变化有明显的系统性减少，年际变化的误差更可能是由于横向边界强迫和不适定横向边界条件对稳态计算模式的激励所致。
[1] The interannual variability of dynamically downscaled analysis and its error relative to global coarse resolution analysis is examined in this paper. The regional model error is shown to significantly contaminate the interannual variability of the seasonal mean. The error occupies a significant part of the interannual variability, particularly during the summer season. Accordingly, the leading modes of empirical orthogonal functions (EOFs) of 500 hPa height in the region differ greatly from those of global analysis. In this paper a variant of spectral nudging, the scale selective bias correction (SSBC) method, is refined to further reduce the error within the observational error. Application of this method in dynamical downscaling reduced the error of the interannual variability of analysis fields (namely, height, temperature, and winds), and made the EOFs of seasonal mean at 500 hPa height agree well with those of the global analysis. Application of the SSBC had a modest impact on model-derived fields, such as precipitation and near-surface air temperature. The improvements in these fields are not as dramatic as those in the analysis fields, but the increased simulation skill is evident. A possible cause of the error in the interannual variability is discussed. No apparent systematic reduction in high-frequency variability is found, and the error in interannual variability is more likely due to excitation of the stationary computational mode by the lateral boundary forcing and ill-posed lateral boundary condition.