资源环境科技发展态势分析平台

Atmospheric reanalysis normally provides a comprehensive record of Earth's weather and climate changes over time, and is extensively used in climate and energy researches. Among various atmospheric variables, clouds play a unique and important role in the atmosphere. However, there are still significant uncertainties on our understanding on cloud properties, and it is still unclear how those newly developed atmospheric reanalyses represent cloud spatiotemporal characteristics. This study evaluates the cloud properties in two atmospheric reanalyses, i.e., the China Meteorological Administration Reanalysis data (CRA) and the ECMWF's Fifth-generation Reanalysis (ERA5), and monthly mean cloud cover from satellite radiometers are considered as the reference. Both CRA and ERA5 generally represent cloud temporal and spatial distributions. To be more specific, ERA5 gives monthly mean cloud cover closely to the MODIS observation over land, but its value over ocean is ~10% smaller than MODIS. CRA underestimates global cloud cover for ~20%, especially over subtropical zones. The differences between the MODIS and reanalysis cloud cover are mostly significant over the polar regions, whereas they can be contributed by the uncertainties of both. Furthermore, the interannual climate variability of cloud cover influenced by ENSO can also be reasonably captured by the two reanalyses, especially ERA5, whereas the CRA and ERA5 cloud cover anomalies are both spreading over a slightly larger region than those from MODIS. Such evaluations are suggested to be extended to even more detailed cloud properties and variations in the reanalysis for further improvements.