Cloudiness climatology in the arctic and subarctic regions from satellite and surface observations and reanalysis data

Total cloud fraction (TCF) over the polar regions of the Northern hemisphere (northward of 60° N) is analyzed using satellite and surface observations and reanalysis data (we use 16 different databases). On average, TCF over all arctic area is 0.70±0.03 from observations. It is higher over the ocean (0.74±0.04) and less over surface (0.67±0.03). Different TCF observational data show better agreement in summer than in winter, and better over the ocean than over surface. The main reason for these discrepancies is the differences in cloud-detection algorithms, especially over the ice/snow surface (it is typical of a whole year) or over the regions with strong surface temperature inversions (mostly in winter). In general, reanalysis systems do not reproduce arctic cloudiness sufficiently.