Climatology of total cloudiness in the Arctic: An intercomparison of observations and reanalyses amg

Total cloud frac­tion over the Arctic (north of 60° N) has been eval­uated and inte­rcom­pared based on 16 Arctic cloud clim­atol­ogies from diff­erent sate­llite and surface obse­rvat­ions and rean­aly­ses. The Arctic annual-mean total cloud frac­tion is about 0.70±0.03 acco­rding to diff­erent obse­rvat­ional data. It is higher over the ocean (0.74±0.04) and less over land (0.67±0.03). Diff­erent obse­rvat­ions for total cloud frac­tion are in a better agre­ement in summer than in winter and over the ocean than over land. An inte­rann­ual vari­abil­ity is higher in winter than in summer acco­rding to all obse­rvat­ions. The Arctic total cloud frac­tion has a prom­inent annual cycle acco­rding to the most of obse­rvat­ions. The time of its maximum concurs with the time of the sea-ice extent minimum (early summer   — late autumn) and vice versa (late spring). The main cause of the disc­repa­ncies among obse­rvat­ions is the diff­ere­nce in the cloud-dete­ction algo­rit­hms, espe­cia­lly when clouds are dete­cted over the ice/snow surface (during the whole year) or over the regions with the pres­ence of strong low-trop­osph­eric temp­erat­ure inve­rsi­ons (mostly in winter). Gene­rally, rean­aly­ses are not in a close agre­ement with sate­llite and surface obse­rvat­ions of clou­din­ess in the Arctic.