The role of Arctic clouds in the recent rapid Arctic warming has attracted much attention. However, Arctic cloud water paths (CWPs) from reanalysis datasets have not been well evaluated. This study evaluated the CWPs as well as LWPs (cloud liquid water paths) and IWPs (cloud ice water paths) from five reanalysis datasets (MERRA-2, MERRA, ERA-Interim, JRA-55, and ERA5) against the COSP (Cloud Feedback Model Intercomparison Project Observations Simulator Package) output for MODIS from the MERRA-2 CSP (COSP satellite simulator) collection (defined as M2Modis in short). Averaged over 1980–2015 and over the Arctic region (north of 60°N), the mean CWPs of these five datasets range from 49.5 g/m² (MERRA) to 82.7 g/m² (ERA-Interim), much smaller than that from M2Modis (140.0 g/m²). However, the spatial distributions of CWPs, show similar patterns among these reanalyses, with relatively small values over Greenland and large values over the North Atlantic. Consistent with M2Modis, these reanalyses show larger LWPs than IWPs, except for ERA-Interim. However, MERRA-2 and MERRA underestimate the ratio of IWPs to CWPs over the entire Arctic, while ERA-Interim and JRA-55 overestimate this ratio. ERA5 shows the best performance in terms of the ratio of IWPs to CWPs. All datasets exhibit larger CWPs and LWPs in summer than in winter. For M2Modis, IWPs hold seasonal variation similar with LWPs over the land but opposite over the ocean. Following the Arctic warming, the trends in LWPs and IWPs during 1980–2015 show that LWPs increase and IWPs decrease across all datasets, although not statistically significant. Correlation analysis suggests that all datasets have similar interannual variability. The study further found that the inclusion of re-evaporation processes increases the humidity in the atmosphere over the land and that a more realistic liquid/ice phase can be obtained by independently treating the liquid and ice water contents.

北极云在近期北极迅速升温中的作用引起了很多关注。但是，来自重新分析数据集的北极云水路径（CWP）尚未得到很好的评估。这项研究针对COSP（云）评估了来自五个再分析数据集（MERRA-2，MERRA，ERA-Interim，JRA-55和ERA5）的CWP和LWP（云液态水路径）和IWP（云冰水路径）来自MERRA-2 CSP（COSP卫星模拟器）集合（简写为M2Modis）的MODIS的“反馈模型比较项目观测模拟器软件包”输出。这五个数据集的1980年至2015年及北极地区（北纬60°N以北）的平均CWPs为49.5 g / m ²（MERRA）至82.7 g / m ²（ERA-Interim），远小于来自M2Modis（140.0 g / m ²）。然而，在这些再分析中，CWP的空间分布显示出相似的模式，格陵兰岛的值相对较小，北大西洋地区的值较大。与M2Modis一致，除了ERA-Interim之外，这些重新分析显示的LWP比IWP大。但是，MERRA-2和MERRA低估了整个北极地区IWP与CWP的比率，而ERA-Interim和JRA-55则高估了这一比率。就IWP与CWP之比而言，ERA5表现出最佳性能。与冬季相比，所有数据集在夏季显示的CWP和LWP更大。对于M2Modis，IWP的季节性变化与陆地上的LWP相似，而在海洋上则相反。在北极变暖之后，1980-2015年期间，低WP值和IWP的趋势表明，在所有数据集中，低WP值和IWP值都有所下降，尽管在统计上并不显着。相关分析表明，所有数据集都具有相似的年际变异性。研究还发现，包含再蒸发过程会增加陆地上大气中的湿度，并且通过独立处理液体和冰水含量可以获得更现实的液/冰相。