NCEP-NCAR和ECMWF再分析南半球中纬度大气变率的不一致性
Discrepancies in Southern Hemisphere Mid-latitude Atmospheric Variability of the NCEP-NCAR and ECMWF Reanalyses
摘要：
在这项研究中，我们比较的代表性南半球中纬度冬季变率的NCEP-NCAR和ERA 40再分析。我们使用经典的Hayashi光谱技术，最近应用到比较不同的光谱子域上的北半球的大气变率的描述。我们检验了两个再分析系统在大气活动性表征上的一致性。在南半球，即使在卫星期间，同化的数据也相对较少，主要是在海洋上空，它们对模式动力学的约束较弱。我们发现在不同的空间和时间尺度的变异性的描述相关的差异。ERA 40通常以较大的方差为特征，特别是在高频频谱区域。在卫星观测前，两次再分析结果之间的差异较大，且是随机分布的，而在1979年以后，两次再分析结果之间的差异是系统性的。此外，在VTPR期间（1973-1978年）观察到一个突然的跳跃，主要是在ERA 40再分析。我们的研究结果表明，今天，我们没有一个明确的图片的冬季中纬度变率在南半球的属性，用于评估的现实主义的气候模式和需求的相互比较研究的IPCC模型的自我一致性的评估在分析的属性的代表。
英文摘要：
In this study we compare the representation of the southern hemisphere midlatitude winter variability in the NCEP-NCAR and ERA40 reanalyses. We use the classical Hayashi spectral technique, recently applied to compare the description of the atmospheric variability in the northern hemisphere on different spectral sub-domains. We test the agreement of the two reanalysis systems in the representation of the atmospheric activity. In the southern hemisphere, even in the satellite period, the assimilated data are relatively scarce, predominately over the oceans, and they provide a weaker constraint to the model dynamics. We find relevant discrepancies in the description of the variability at different spatial and temporal scales. ERA40 is generally characterised by a larger variance, especially in the high frequency spectral region. In the pre-satellite period the discrepancies between the two reanalyses are large and randomly distributed while after the 1979 the discrepancies are systematic. Moreover, a sudden jump in the VTPR period (1973-1978) is observed, mostly in the ERA40 reanalysis. Our results suggest that today we do not have a well-defined picture of the properties of the winter mid-latitude variability in the southern hemisphere to be used in the evaluation of the realism of climate models and demand for an intercomparison study for the assessment of the self-consistency of the IPCC models in the representation of the analysed properties.
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