多瑙河存在吗？各种区域气候模式和气候数据集给出的现实版本
Does the Danube exist? Versions of reality given by various regional climate models and climatological datasets
摘要：
我们对嵌套在同一大气全球环流模型（AGCM）同一运行中的几个区域气候模式（RCM）进行了相互比较和验证分析，以了解它们对1961-1990年多瑙河流域水文平衡统计特性的代表性。我们还考虑了驱动AGCM产生的数据集，从ECMWF和NCEP-NCAR再分析。水文平衡是通过对感兴趣区域的降水和蒸发场进行积分来计算的。RCMs之间存在很大的差异，每月的气候以及平均值和变化的年度平衡，只有少数数据集是一致的，在其三角洲的多瑙河观测流量值，即使驱动AGCM提供了一个很好的估计。由于所考虑的方法依赖于质量守恒原理和绕过的细节的空气-陆地界面建模，我们建议，大气成分的区域气候模型仍然面临困难，即使在一个相对较大的规模代表水量平衡。它们在较小的河流流域的可靠性可能更成问题。此外，由于一些模型的水文平衡估计与径流场得到的降水和蒸发不一致，陆地模型的一些不足也是显而易见的。NCEP-NCAR和ERA-40再分析结果在很大程度上不足以代表多瑙河流域的水文，无论是重建长期平均值还是季节周期，在任何意义上都不能用作验证。我们建议，这些结果应该仔细考虑的角度审计气候模式和评估他们的能力，模拟未来气候变化。
英文摘要：
We present an intercomparison and verification analysis of several regional climate models (RCMs) nested into the same run of the same Atmospheric Global Circulation Model (AGCM) regarding their representation of the statistical properties of the hydrological balance of the Danube river basin for 1961-1990. We also consider the datasets produced by the driving AGCM, from the ECMWF and NCEP-NCAR reanalyses. The hydrological balance is computed by integrating the precipitation and evaporation fields over the area of interest. Large discrepancies exist among RCMs for the monthly climatology as well as for the mean and variability of the annual balances, and only few datasets are consistent with the observed discharge values of the Danube at its Delta, even if the driving AGCM provides itself an excellent estimate. Since the considered approach relies on the mass conservation principle and bypasses the details of the air-land interface modeling, we propose that the atmospheric components of RCMs still face difficulties in representing the water balance even on a relatively large scale. Their reliability on smaller river basins may be even more problematic. Moreover, since for some models the hydrological balance estimates obtained with the runoff fields do not agree with those obtained via precipitation and evaporation, some deficiencies of the land models are also apparent. NCEP-NCAR and ERA-40 reanalyses result to be largely inadequate for representing the hydrology of the Danube river basin, both for the reconstruction of the long-term averages and of the seasonal cycle, and cannot in any sense be used as verification. We suggest that these results should be carefully considered in the perspective of auditing climate models and assessing their ability to simulate future climate changes.
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