The relationships between Arctic sea ice and cloud-related variables in the ERA-Interim reanalysis and CCSM3

This study uses reanalysis data from ECMWF ERA-Interim and GCM output from the CCSM3 to investigate how sea ice and clouds interact locally (within individual grid boxes) and whether similar variability between the two datasets is captured. During autumn (October), the vertically integrated low cloud amount increases over increased sea ice in the reanalysis, but decreases in the GCM output. Closer inspection, however, reveals that both datasets have more low cloud cover over increased sea ice within the lower boundary layer (1000–925 hPa for the reanalysis and 1000–975 hPa for the GCM output), but they differ in their integrated response within the lower troposphere. These results highlight the differences between the datasets and show the importance of understanding where cloud changes occur, because clouds vary in their effect on the radiation budget as a function of height.